Atari Guru Dave Small Guides You On A Tour Through The Power And Speed Of The New TT030
BY DAVE SMALL
PHOTOGRAPHY BY CHLOE ATKINS
Author's Disclaimer: In my work at Gadgets by Small, I've come into close contact with many of the new features of the TT in Gadgets' new products, such as the SCC chip, LocalTalk (formally Appletalk) and the 6830 and its burst-mode RAM ability. While this gives me an informed viewpoint from which to review the TT, I've refrained from commenting about areas of the TT where Gadgets could be perceived as competing with Atari.
Long awaited by ST users, the TT030 represents Atari's latest effort in their Computer line based on the Motorola 68000-series microchip. The TT made its "official" debut in the United States at Fall Comdex last November; projected availability, which depends on FCC approval, is in early 1991.
The TT can be perceived as many different machines rolled into one. It is intended as a faster ST with more memory and capabilities: a mix-compatible workstation: a Localtalk- (formerly Appletalk) equipped, hence networkable, computer as a network server: and a VME-bus expandable computer.
The TT fits into these categories, but each ends up with "extra parts" from its other functions. For instance, it works as a faster ST but has a VME slot and Localtalk connector that ST software does not currently support . It works as a Unix workstation, but has display modes that are nearly useless for Unix (ST low-res. for instance).
This is good, in that the TT is multifunction; it isn't simply a souped-up ST. It's bad, in that all the extra hardware is costly. At $2,995 announced retail base, the machine is pricey to an ST audience wanting only a more powerful ST.
Market trends will affect the TT as well. Atari's slogan of "Power Without The Price" is going to he affected by the price competition entering the computer market. The market is no longer in the same place it was when the 1040ST broke records by offering a megabyte of memory for under $1,000.
For instance, the Next Unix workstation selling at $4,995 offers a next-generation, object-oriented software-development system (NextStep), that will tempt users facing a $3,000 TT. Sun's Sparc (RISC-based) Unix workstations, in the same price range as Next, offer considerably more raw performance than the (68030-based) TT - or almost anything else. The new Macintoshes, particularly the "low cost" LC, offer performance and the vast Mac software base. And finally, the endless 80386 and 80486 clones available around $3,000, with the largest software base of all, will prove to be the stiffest competition for the TT.
Hence, it may be that Atari should have specialized with a line of machines, each dedicated to one function (faster ST: Unix workstation; network server; VMF bus station), to remove the expensive Parts not needed for the particular function. However, the TT represents Atari's marketing choice to roll all these functions into one box, for good or bad.
Let's examine the TT with an eye toward these different functions. Since the average START reader is ST oriented, you may find some of this equipment unfamiliar; these may be pieces relating to other functions (for instance, VME). I'll try to explain these parts in familiar terms.
(I'm not qualified to review the VME board. Hence I'll simply note that the TT's VME slot is capable of accepting half-height VME boards [called 3U boards].)
Unix Anyone?
TT Unix was not released nor otherwise available to me by the time
this review was written - Specifications on it seem to vary from month
to month, as to which release of the AT&T Unix operating system it
will support (version 3.0 or 4.0), if X-windows will be supported, which
Desktop "look" might be included, and whether or not Berke1ey extensions
will be supported. I feel Unix requires a 50MB hard disk just to begin
with, with more being far preferable - particularly if you join data-intensive
areas such as Usenet or other networks - and the more RAM the better; more
RAM helps prevent hogging down due to disk paging. 8MB seems to work well;
the TT gives you the option of four or 16 in TT RAM, where I assume Unix
will he located, for speed.
Walk-Around
Let's begin with a quick walk around of the TT, going clockwise from
the front.
The keyboard: The detachable TT keyboard is familiar to ST users; everything's the same. The one exception is that the function keys are now unslanted and stand far above the other keys. Since the slanted function keys on the ST series often resulted in missed keypresses. this is probably a good change. The keyboard has a good feel to me; however, the feel of a keyboard is completely subjective, from those preferring an IBM-style "click" board to those preferring an utterly soft "mush" board, so you'll have to form your own opinions of this one. The keyboard does offer "positive action"; in other words, the keyboard lets you know when you've pressed the key far enough to activate it.
The right side of the keyboard sports the normal mouse (or Joystick 0) DB-9 connector, the left side the Joystick 1 connector.
The keyboard cable connects from the right side of the keyboard to the left side of the TT computer, unfortunately, via a coiled cable. The keyboard can he locked to the TT if you desire, with some finagling of the keyboard cable.
The Case: Connected to the keyboard cable, of Course, is the case. Opinions on the case are heated and diverse; it is certainly a unique design, something between a wedding cake and a toaster in appearance.
The contortions required of the shielding inside the TT to fit within this case mean there is almost no free room available inside for any aftermarket expansions. Don't disassemble the TT unless you absolutely have to; this is not an easy machine to take apart.
The Floppy Drive: In the front is a double-sided floppy disk drive, It is presently 720K. the same density as ST floppy drives. Atari reportedly was going to offer 1.44MB drives (high density). much like the IBM and Macintosh; however, the 1772 controller chip Atari uses cannot consistently operate at this rate.
The Monitors: The normal monochrome (SM124) or color (SC1224) ST monitors will not run off the TT and there's no place to plug them in. Instead, Atari uses a VGA-style monitor for output, and will market an Atari-brand monitor with stereo speakers. I did not have the opportunity to use this monitor; instead, I used a PanaSync C1331 monitor, which I feel offers fine video performance at a fair price. Any multisync monitor with a 15-pin connection should work fine.
The TT supports the old ST video-resolution modes, if not the old ST monitors. This is part of a deliberate decision permeating the TT's design to remain as compatible as possible with ST software. This effort is as successful as it could have been. Atari claims that 75 percent of the ST software in their extensive library of third-party products works fine on the TT; I had somewhat lesser luck with the TT, but in my usage I was not using many popular ST applications.
The TT also has its own video modes, which provide higher resolution and more colors. More on these later; we're still touring the machine.
A two-page monochrome monitor (designated the TTMI94), may be connected to the TT. This provides excellent-quality video for applications compatible with it, very comparable to the Moniterm for the Mega. (Unconfirmable rumor has Moniterm manufacturing these monitors for Atari; in a comparison with our Moniterm, they appeared very similar.) However, a key point: old Moniterms will not connect to the TT Apparently Moniterm and Atari chose incompatible video frequencies and video-cable transmission methods; so far, no third-party developer has been able to Provide an adapter.
Incidentally, with any monitor, be careful of sitting it on top of the TT. We have had frequent experience with crashes caused by apparent circuit-board flexing due to monitor weight. We can't isolate the problem. If your TT experiences frequent weird crashes, try moving the monitor off and behind it. (Editor's Note: This problem may also be caused by a lack of effective radio-frequency shielding on the bottom of the TTC1434 monitor which apparently can disrupt floppy-disk action. The solution the author suggests should help.)
Internal SCSI Hard Disk: The right side of the machine offers no connectors, and only one interesting point. The internal 3.5 inch hard disk, which is connected via SCSI (rather than the "normal" Atari ACSI), sits in the right-hand portion of the case, isolated from the rest of the unit by a slice taken out of the case.
Because the internal hard drive is standard SCSI, there is no need for an "Atari Host Adaptor" to connect the usual hard disks to the Atari. In addition, other popular SCSI peripherals, from hand scanners to Ethernet adaptors, can he directly connected to the DB-25 SCSI connector on the back of the Atari. (SCSI is normally 50 pins, but half of those are ground for noise suppression, and thus SCSI can easily be wired to a 25-pin connector.)
This internal hard disk can he easily removed - it takes just one screw to pop the cover, then unplug the drive from its 50-pin SCSI connector - and replaced with another. Given the plethora of 3.5 inch SCSI units, this gives you the option of going to a much larger hard disk. Also. you can add more storage on the SCSI or ACSI daisy-chains should the internal hard disk not give von enough room.
Out Back
Moving around to the hack of the TT, the DB-25 SCSI connector is the
first thing you see. Atari has persisted in its policy of moving the Power
and Reset buttons around on different machines.
The DB-25 connector appears to be wired identically to a Macintosh DB-25, which is very good news for those of you searching for peripherals; Mac SCSI equipment should be able to plug right in. Note that software is required. For instance, a Mac hard disk with a DB-25 connector will still require formatting-software and a driver to use on the TT. Atari Provides software to initialize and use some drives.
Atari must be commended for sticking to industry standards for its connectors in the TT. By making the TT SCSI connector Mac compatible, users do not have to purchase or make kludgy adapter cables.
Moving across the back of the machine, you'll find two cooling fans. The TT has twin fans, a move I highly approve of, since many STs I have encountered are sensitive to heat, and since the many components in the TT put out quite a hit of heat.
Next, we find the familiar 14-pin DIN floppy connector; as with the recent STs. there is one internal and one external drive supported by the TT.
Next to the floppy connector is the DB-l9 ACSI hard-disk connector; you can hook ST compatible peripherals here.
Next comes the 15-pin video connector. This is a pretty standard IBM-style VGA hookup used on many monitors.
Next, we have four built-in serial ports, labeled Modem 1, Modem 2, Serial 1 and Serial 2. There's really a fifth serial port. the LocalTalk connector, as we'll learn in a moment.
You may he asking why the machine has five ports. There are several good reasons. First, when used as a Unix box, four terminals can be connected to the TT easily for multi-user applications. Or, when used as a multi-user BBS, the TT can easily hook to four modems.
Second, this allows connection of serial printers and other serial peripherals without the cable-changing or switchboxes needed on the (single serial port) ST.
Third, the serial ports basically come free of charge once some necessary hardware was added, so why not make them available? Here's the situation. Motorola makes a chip called an MFP (Multi-Function Peripheral). The MFP does many neat things, among them interrupt controlling, giving an easy-to-use programmable I/O port, and provides a single serial port. Atari used the MFP in the ST and thus replaced many chips with one chip, a good move.
In the TT, more interrupt handling was required, so two MFP's are onboard (they are designed to daisy-chain like this), and we get another "free" serial port - so why not let the user plug into it? Atari did so. The connectors Modem 1 and Serial 1 are the two MFP ports.
Two things to keep in mind: Modem 1 is the fully ST compatible Port, with all the strange RS-232C handshaking wiring. Modem 2 and Serial 1 are "three-wire" ports. featuring only input and output, without strange wiring; Serial 2 features full handshaking. It gets a little confusing.
Also note that these are DB-9 connectors, not the DB-25 connectors you're used to on the back of your ST. You'll require an adaptor cable. Fortunately, the wiring is the same as the IBM AT serial port, so you can pick up these adaptors at nearly any computer shop.
The Modem 2 and Serial 2 ports come from an SCC chip. This Zilog chip is the absolute cat's meow for serial communications; which it can do at incredibly fast rates. For instance, the ST's serial chips "max" out at 19,200 baud, or roughly 1,920 characters per second; the SCC "maxes out" at over 900,000 baud, or 90,000 characters per second!
At 90,000 characters per second, you begin to push the ability of the processor to feed the chip. As fast as a 680x0 processor is, stuffing nearly 100,000 characters per second into a port begins to push it. So, the Atari engineers built in DMA, or Direct Memory Access which just means that something can access memory directly, without the processor's help.
Video can access memory directly. That's DMA. (We'll discuss this at length shortly). The disk drive can access memory directly. That's also DMA. That's why your ST, hack in 1985, could run disk drives flat-out whereas the Mac Plus could only handle them at 1/3 speed; the CPU wasn't needed for the actual transfer. Sound can be driven directly from memory; DMA. And finally, the SCC serial chip can be driven from memory with DMA.
Thus, you can set up DMA, tell the SCC to "Go!", and go do other things with your CPU while the SCC and DMA work together to pull bytes from memory and send them out, or gather in bytes and store them. This is really neat stuff as opposed to tying up the 68030 to handle serial work; a good analogy would be a printer buffer.
Atari wisely used the SCC chip because they wanted to build in a network connector to the TT. One of the most popular networks (I have seen it reported as the largest installed base of any network) is LocalTalk, which used to be called Appletalk, originally for the Macintosh. The SCC chip is used in the Mac to generate much of the LocalTalk talk, and the information is sent differentially, with RS442, instead of RS232. Finally, it all has a different connector, a DIN-8, (with a circular pattern of pins) instead of the familiar DB-25 or DB-9 with two) rows of pins.
Atari does not at present offer any software to run LocalTalk. In other words, it has the hardware, not the software. Without the very complex Appletalk Protocol software (it's a 10-layer deep protocol), the ST simply cannot work on a LocalTalk network.
As with Modem 1/Serial 1, Modem 2 is a three-wire, no handshake interface; Serial 2 is full handshake.
Now, of course ST software hasn't really been written to handle more than one modem port, with few exceptions (Double Click's multiport expander for one). So Atari's given you the option of hooking up what the ST software will consider "the serial port" to any of these ports through "Bconmap," in software, or even through a new Control Panel option. Hopefully new software will use these multiple ports.
And yes, nearing the left side of the Atari, right where it's least accessible (directly centered under the monitor), is the power switch.
Continuing on with no comment, we encounter the second fan, and the two stereo sound ports; the TT has the STE's DMA-driven stereo) sound options.
To The Left
On the left we find:
The Reset switch, hidden at the far hack behind any LocalTalk cabling, to prevent accidental or intentional presses; the LocalTalk DIN-8 circular connector; the two MIDI ports; and the cartridge connector, which is fully ST compatible. In terms of physical room, even the large Spectre GCR cartridge fits fine, so most ST cartridges should work okay. And last, the key board connector cable, which should have been on the other side to match the keyboard.
It's time for a look inside the TT now; there's a lot of new stuff inside, from the new MC68030 on down.
Inside the TT: Video
Because I've already mentioned a good deal of what's inside the TT,
I don't have to say much about, for instance, the serial ports. The TT's
central design, in my opinion, revolves around this: speeding up a computer
and video system that is very difficult to speed up.
Few people appreciate how incredibly difficult it is to get a video display up on a TV screen and keep it there rock-steady. The problem is that the display is generated by only one dot. It starts at the top left of the screen, streaks across horizontally, moves down a line, streaks across again, and so forth, "painting" the screen. The dot gets brighter or softer to control intensity at any point, and is aimed slightly differently to generate color dots on a color monitor.
However, the image rapidly begins to fade out. The computer must redraw that image around 60 times a second, or better, to keep the image up there.. (If it's under 60 times a second, the user will perceive "flicker" and begin to get a headache. Some countries, by law, require over 70 times a second on monitors.
Let me give you some details here on just the ST's monochrome monitor. It has 400 scan lines horizontally, each about a foot long, with 640 dots on each. This whole thing is redrawn every 1/60th of a second.
One "refresh" is thus 400 feet of scan line, done 60 times a second, or 24,000 thousand feet per second. That's 4.5 miles! In an hour, your video) beam has traced 16,363 miles across your screen, over and over.
The computer is beating itself to death generating that video beam. Doing video is so hard for a computer, requiring so much very fast stuff, that computers are designed around doing video! The Atari ST shares a basic design with many other computers, such as the Apple II. The basic video image is stored memory. Memory speed is twice what the processor requires; half of the memory's speed is used feeding the processor, the other half is used feeding video. Doing video is so difficult that 16MHz (eight-million access/second) memory is used on the ST. shared between the 8MHz CPU and the 8MHz video; they get alternating memory accesses. The ST ends up pumping out 32K of video information each 1/60th of a second to generate the screen image.
Enter the TT. It does the "old, slow" video modes the ST did, as well as new modes that require much more memory (158K, instead of 32K). Yet it still has to get that video out in 1/60th of a second! A quick check with a calculator will show you that this would completely max out even 32MHz memory, leaving no time for a CPU to access it. So Atari had to do something.
Memory is organized with a certain. number of "bits across"; this means that every access to memory gives back a certain number of bits. On the 8-bit Atari, it was eight. On the ST, it was 16. On the TT, it's 32. Thus, for each of your cycles, you get much more information, adding a hidden speed-up to everything.
But the TT video circuit fetches 64 bits per access! It does this with a special latching system. With this 64-bit fetch, the TT is capable of giving half of system memory to the 68030 processor, and half to video once again - but now tile video is much, much better.
Here's a summary of the TT's video modes.
ST Modes:
320x200 16 colors ST Low
Res (Color)
640x200 four colors ST Med Res (Color)
640x400 one color ST High
Res (Mono)
New TT Modes:
320x200 16 colors
640x200 four colors
640x400 two colors (Duochrome)
640x480 16 colors
1280x960 one color TTM194 monitor
required
320x480 256 colors Many-color-mode
from a palette of 4,096.
There are also some interesting modes on top of these, like "smear mode." In this mode, the computer generates the first color on the screen that it finds in memory (again, starting at the top left), then continues making that color until it is specifically told a new color. (Techies: 0 in display memory means don't change colors). Why is this important? With very little processor time you can "fill" entire areas with color - without doing the customary fill to the corresponding display memory. This should allow some spectacular animation work.
There's also a way to change the machine into grey-scale mode, where instead of 256 colors, you get 256 shades of grey.
Incidentally, there is no Blitter in the TT. It was the opinion of the engineers that the 68030 processor is so fast that there was little to be gained by a Blitter. Even the two faster-video programs, Turbo-ST and Quick ST, have been updated for the TT, and yield very high-speed improvements.
The video appears extremely stable, without flicker or jitter. For instance, the Desktop simply appears sharper and more colorful, the result of higher resolution, in normal TT color mode. If only the ST's Moniterm monitor would plug into the TT; users who could afford Moniterms are likely TT buyers, but may be reticent to purchase another monitor that differs so slightly.
A New Type Of Memory
You'll recall that in the ST and TT both, we have main memory (ST memory),
shared evenly between video and the CPU, which cuts down machine performance
-there are times the CPU could use memory that video has. In the ST, the
68000 microprocessor very often hit memory just as its "time slot" opened
up, so there wasn't much speed degradation; the TT has a much faster 68030,
hitting memory much more often, and is thus more likely to be slowed down.
The TT's designers knew that the up to 4MB of ST memory would likely bottleneck the 68030, which is capable of awesome speed; the 68030 is the heart of many hot workstations (Sun-3 and HP equipment, for instance). So they added another space for "TT memory." This memory has nothing to do with video; for instance, you can't have a video image in TT memory and display it. However, this opens up TT memory to full-throttle access from the 68030; it about doubles the speed of programs running within it.
The 68000 processor in the ST was capable of addressing 16MB of memory. The 68030 in the TT is capable of addressing 256 times as much memory, or up in the gigabytes (billions of bytes). In the TT, the first 4MB of memory are ST memory, Then there's an open space reserved by Atari for other things. Starting at the 16MB border, there is TT RAM, which comes in either 4MB or 16MB sizes, depending on which chips you use. (The 1MB DRAM SIMMS so common today yield 4MB; the more expensive, but becoming affordable, 1MB DRAM SIMMS yield 16MB of TT RAM.)
This is also memory that's 32-bits wide, so everytime the 68030 hits it, it gets four bytes (eight bits each).
But there's something better. The 68030's designers built in a turbocharger if you design your hardware to use it, called "burst mode." And the TT uses it in TT RAM.
Burst Mode
Normally, the 68030 goes through a number of gyrations to "fetch" the
instructions it's going to execute out of memory. All these gyrations end
up taking many memory cycles, and even at millions per second, that ends
up slowing things down.
In burst mode, the 68030 pulls in 16 bytes, or four "longs" (a long is 32 bits, the size of TT memory) in just five cycles; one to set things up, one to fetch the first, the remaining three to fetch the other three. This is far, far better than the normal instruction-fetch mechanism. The 16 bytes are fed into the "instruction cache," a place inside the 68030 I'll talk about more later, and executed at top speed.
Adding burst mode is really warp-drive stuff! The type of RAM the TT (and every other modern computer) uses mostly is "dynamic RAM" (DRAM); DRAM must periodically halt and see to its own needs ("precharge"), during which times it's off limits to the CPU. There is also "refresh" time, where the DRAM keeps its memory contents from fading. This all boils down to TT memory not being always ready for the 68030. With burst mode, there's no need for the 68030 to go main memory for the next 16 bytes of program: it's pulled inside the 68030. Thus the 68030 can execute at maximum efficiency.
|
A Sneak Peek At Atari's Middle Child By John Nagy |
| Atari Corp. surprised even their own developers
by announcing the Mega STE at last fall's Comdex. Scheduled for an early
1991 release, the Mega STE is identical in appearance to the TT, but in
ST grey rather than off-white. The base configuration was not set at press
time, but it will most likely include 2MB RAM, a 40MB internal hard drive
and run TOS 2.2 or higher with the Atari NewDesk enhanced GEM Desktop and
Extensible Control Panel. The Mega STE's central processing unit is a Motorola
68000 running at 16MHz, which is switchable (with or without static RAM
cache or down to 8MHz for compatibility with "problem" software, such as
Spectrum 512).
The Mega STE is, above all else, an STE and you may assume that any feature on the new machine is the same as on the 1040STE unless specifically mentioned here. The Mega STE does not include the new TT resolutions, larger on-screen color scheme or video outputs. The Mega STE does include the STE's standard 4,096-color palette with the same monochrome high resolution, four-color medium resolution and 16-color low resolution modes with hardware scrolling. Also like the STE, genlock is available without modification, but requires JRI's external hardware. The internal floppy is 720K.
Ports include the full complement of the 1040STE minus the analog joystick ports. Additional ports are: LAN (Appletalk compatible, same as the TT); two modem in the new smaller connector configuration that is becoming standard (although the second port shares internal hardware with the LAN port that may make simultaneous use with the LAN impractical); and a VME Bus Card (same as the TT and accessible from the rear of the machine). The Mega STE does not include the true SCSI external hard-drive port featured on the TT. Instead it features the Atari DMA port, now labeled ACSI (Atari Computer Special Interface). Internally, the Mega STE includes a 68881 math coprocessor socket. All other ports are the same as the STE, including an RF output jack to run a TV or VCR, and composite video available on the monitor line just like the older ST standard. The MIDI- and cartridge-port locations remain unchanged. The power switch for the Mega STE is placed in the center of the back panel. The reset button is within easy reach, on the left side of the machine. The Mega STE keyboard is the same as the TT. The function keys are now much more distinguishable due to better spacing, clearer markings and finger-stops at the left edge of each button. The mouse port is on the right edge of the keyboard; the keyboard cord exits to the right. At press time, pricing for the Mega STE was still to be determined. Sources at Atari say that the base Mega STE with a monochrome monitor will retail for less than a similarly outfitted Apple Mac Classic, but at double the speed. The street price for a Mega STE without monitor is rumored to be around $1,200. |
|
Mega STE, call for price. Atari Corp., 1196 Borregas Ave., Sunnyvale, CA 94088 (408) 745-2000 |
By the way, it's the nature of DRAMs to be slow to access; for instance, after accessing one location, the RAM must rebuild up the electrical charge in that location which was used up by you reading it. Otherwise, repeated accesses would literally drain that RAM location to zero! (This is called "precharge"and I am simplifying a highly complicated subject.) In order for burst mode to work, you need to have "nybble mode" RAM chips, which are definitely not run-of-the-mill SIMMs as they're advertised in many magazines. A "nybble" is four bits (the name is from a horrid pun: A nybble is half of a byte). When you access regular RAM, you get one bit, and eight of them together gives you a byte (the TT uses 32 together to give you a "long" at once). When you access a nybble-mode RAM, when you access the first bit, it also sets you up to grab the next three bits without much delay at all -which, as you can see, is perfect for burst mode, which has to grab four bits from each of the 32 RAM chips very very quickly.
Now, because this memory is dedicated to the 68030, you can't do some things from it: remember, we don't want to slow it down by hanging other stuff on to it. Thus, you cannot do DMA to the TT RAM. This means you can't have video memory in it, you can't have a sound buffer being played from it through DMA, you can't have the SCC push/pull bytes with it, and you can't use ASCI hard- disk/floppy-disk DMA with it. (In an odd exception, you can do SCSI DMA to it; I have no idea why this ended up this way. Thus half the hard disk connections to the TT, ACSI [ST hard disks]. cannot touch TT RAM: the other half, SCSI [TT hard disks] can touch TT RAM.)
But, and this is key. your program can live in TT RAM and run from there. This means your program, instead of poking along with the video circuits preventing the 68030 from getting to it a lot, suddenly goes into turbocharged mode - and with burst mode, it's like adding a bottle of nitrous Oxide (oxygen super-enhancement).
If the program follows the above rules (no DMA to TT RAM), it usually lives and works in TT RAM just fine at far higher speeds. Up to an eight-times performance improvement is possible.
Memory Allocation
Atari has helped you out in this TT RAM business. There's now three
"flags"(a flag is just a yes/no switch) stored with any program you use.
You're probably already familiar With one such bit: it controls whether
or not the area a program is going to he loaded into is zeroed-out (cleared)
first. If this is not needed, a program load is much, much faster.
In the TT, a new flag tells the computer whether or not it should even try to load the program into fast RAM. With this, you can tailor programs that break in TT RAM to load to the slower ST RAM.
The next bit tells the TT that if the program requests memory, should
it get TT memory or ST
memory?
This one is a bit more subtle. Programs request memory for variety of reasons. One such reason is to set up a place to do work from disk, display a picture, or play a sound. If the programs do this, they can't do it with TT RAM. since that's not allowed. So while the main program can run in TT RAM and enjoy that, if it needs to set up video by itself, you can set it up to get that memory from ST RAM.
On the other hand, if the only memory it needs to request are for data
tables (say, a spreadsheet that uses regular video), the memory request
can come from TT RAM, and zoom along far faster.
|
TT030 $2,995 (4MB RAM 40MB hard disk). Atari Corp., 1196 Borregas Ave., Sunnyvale, CA 94088 (408) 745-2000 |
If you re wondering, the TT knows how to load programs into TT RAM from disk: it uses ST RAM as an intermediate stopping place. The program is loaded into ST RAM using disk DMA, then block-moved into TT RAM. This block-move is one thing that the 68030 excels at with its cache; see below for more on the cache.
Caches
The 68030 features both an instruction and data cache. All this means
is that the 68030 remembers the last 256 instructions it accessed, and
the last 256 places it worked with data from (and the data). When the 68030
goes to get its next instruction, it first looks to the cache, asking,
in effect. "Can you give me this instruction fast, or do I have to go to
RAM and wait awhile?". If the instruction is in the cache, the 68030 immediately
executes it; if the instruction accesses data that's in the data cache,
the 68030 doesn't have to worry about RAM at all.
When the 68030 kicks into burst mode and loads 16 bytes at top speed from memory, it's loading this instruction cache. Since 16 bytes are loaded, the 68030 doesn't talk to anything at all for a bit; it just buzzsaws through those instructions at top possible speech.
On the TT Desktop, where the Blitter pull-down menu option once was, there is now a "Cache" option you can turn on or off. When on, the machine displays blistering speed; when off, the machine is still faster than the ST. but not that much faster for the price: that's because video "contention" is forcing the 68030 to wait so much.
32MHz?!?
When the TT was originally designed, it was meant to be a 16MHz machine;
that means everything in the machine was to be rated to run 16 million
machine cycles per second. The ST's hardware chips (say, DMA or video for
instance), gasp and die when asked to) run any faster than eight million
per second; even the accelerator hoards deliberately slow to 8MHz from
16MHz when accessing hardware.
At the last minute, Atari changed out the 16MHz 68030 to a 32MHz 68030, and added enough hardware (a few PAL chips and stuff) to make that work. However, all those other custom chips, from the TT RAM controller to the new video chip to the new DMA chip, were all 16MHz, and redesign would he extremely costly- and this machine was already late to get out the door.
So, only the 68030 runs at 32MHz. The rest of the machine runs at 16MHz. Now you see the importance of those caches. They are onboard the 68030 chip, and run at 32MHz: if the program largely fits inside the cache, it will scream along at 32MHz. If it doesn't, it will run at 16MHz, Certainly, burst mode and TT RAM help at 16MHz as opposed to video RAM, but 32MHz is still a long way from 16MHz. Your speed absolutely will vary depending on what software you run.
Be particularly wary of benchmark programs that claim to measure the machine's speed! If the benchmarker's measuring loop fits into that 2S6-byte cache, it'll show a 32MHz machine; if it goes even 258 (or more) bytes, it'll show a 16MHz machine, which I assure you will baffle the user.
What's really needed, in my opinion, is for at least a 16K cache board to be made available for the TT. 16K caches show a very high "hit rate" (the percentage of times the processor finds what it wants in the fast cache, rather than in slower RAM): even more cache memory doesn't really help that much more. After-market manufacturers are already showing an interest in such a product. This would be a worthwhile addition to the TT if properly done.
punch with five times the
resolution and four times
the speed of the "old" ST.
Conclusion
The computer market moves very rapidly these days. Sun Microsystems
considers its primary advantage to be a six-month lead on the market! (Sun
is an extremely profitable workstation manufacturer). A 32MHz machine is
competitive right now, as I write this, December 1990; in not very long,
it will be considered slow, as 50MHz 68030, new generation 68040, and 80486
machines reach the marketplace. Machines dwindle into obsolesence very
quickly.
The ST machines were at the leading edge of this curve, and are now far behind it, even for "home computers"; very often a "home computer" is now someone's old office IBM PC or clone. Still. Atari made its reputation, and the cover of Byte Magazine, offering "Power Without The Price"; back in 1986, a megabyte of memory and an 8MHz 68000 were very good for $1000.
Now we're in a market where the TT is not going to remain competitive for long without some new engineering. Memory is ultracheap compared to 1986. Speeds are going up at remarkable rates, and PC clones live or die based on what clock speed they run at; right now, 33Mhz 386s and 25MHz's 486s are at the competitive edge. In the Motorola market, 50MHz 68030's are already available, but too costly for any but expensive machines to use. In my opinion, the TT is uncomfortably close to the trailing edge of saleable curve. Having a 32MHhz processor and a 16MHz "bus," or the other components, is uncomfortable at best. Atari has its hardware engineering work cut out for it to bring things to a 32MHz or higher spec; clearly they need to aim above even 32MHz to be with or ahead of the market when the new machine arrives. Call it the "UT" (ST, TT, UT) but it needs to happen.
Atari is also getting behind in software engineering. Virtual memory and multitasking are considered things that manufacturers are working toward, be it with Windows 3.0 for the IBM & clones, System 7 for the Mac, or whatever. Atari has fine software engineers, in my opinion; what it does not have is enough of them! The TT must be considered as an interim machine until the next machine, my UT, is designed and released. It spent too long in gestation, for a variety of reasons. At a $3,000 price point, the machine is far too uncomfortably close to such powerhouses as the new Next or Sun Sparcs, and even ahead of very powerful IBM clone boxes. And it is far too far away from the average ST user, comfortable with $1.500 major hardware purchases.
So my conclusions about the TT really are dependent on what Atari does next. The TT proves that Atari can still turn out hardware that has neat features and speed; remaining to be proven is if the TT can be improved upon, in software and hardware, and priced at a point where the US. market can support it.
Dave Small is owner and operator of Gadgets By Small, maker of the legendary Spectre GCR Macintosh emulator for the ST. After nearly a year absent from the pages of START, Dave's original and informed prose is a welcome sight.