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AT&T's Back in the PC Game!

Nick Stam

Looking back to 1983, just before the breakup of the Bell System, AT&T formed its American Bell subsidiary in preparation for competing in unregulated markets against various telecom equipment companies, and also against the likes of established computer vendors such as IBM and DEC. By 1984, American Bell became AT&T Information Systems (a better name for selling computers, along with the fact they were forced to drop the "Bell" name in the breakup). The computer media realized AT&T had the deep pockets (even after divestiture) to compete with IBM. Various incarnations of "Clash of the Titans" headlines were seen popping up everywhere, and the world braced for AT&T to take a healthy chunk of the desktop computing market away from IBM. Upstarts like Compaq and later PC's Limited (which was an enigma to polished AT&T execs), didn't stand a chance of holding sizable market shares once AT&T entered the picture. The PC business would be dominated by the two titans.

AT&T worked feverishly to develop PC systems based on the 8086 and 80286 in conjunction with Olivetti in the mid-80s, and also developed a broad line of minicomputers (the 3B series), some of which were highly fault-tolerant and powerful minicomputer systems (the kind of computers that kept the most reliable and largest computer/communications network in the world operating – the Bell phone system). So far so good.

AT&T thought they could compete head-on with IBM's desktop PCs by selling systems with slightly better performance and features at a reduced price (about 15% cheaper at retail). And AT&T's senior product and lab development managers deemed that 100% hardware compatibility with the IBM PC line was not a strict requirement, allowing room for hardware innovation, as long as all x86 software and PC/XT-bus expansion boards worked properly. Again, interesting strategy, if it was fully compatible.

You may recall the video system in their original PC 6300 line as being impossible to upgrade without first removing the video card (which also happened to bind together the motherboard on the underside of the desktop system unit to the top-facing expansion bus board), getting a special u-turn adapter to connect the motherboard/bus board, installing a PAL chip upgrade, and replacing/upgrading the BIOS chips (Flash BIOSs didn't exist back then). But the video was so far superior to standard IBM PC graphics, that the upgrade limitation wasn't deemed a big problem at the time.

Of course, history will tell you that AT&T was highly unsuccessful in their foray into the desktop computer business from the mid-80s to early 90's for a variety of reasons, losing over $1B by the late 80s alone.

Present-day AT&T management studied their prior blunders, and realized that the main reason the company failed in the PC business was lack of 100% IBM PC compatibility (or industry standard architecture as termed today), and lack of end-user tweakability and customizability. They realized their old PC 6300 Plus had the proper underpinnings (minus the video problem), as it was their most successful PC product ever, and if they could expand on its customizable feature-set, bring it forward in time, and add a "+" sign to its name (they considered "Turbo" too), yielding the catchy "PC 6300 Plus+", it would be immediately recognized among millions of computer users.

While planning the design of their new PC 6300 Plus+ product, AT&T execs insisted that their developers build compatible hardware capable of running all PC software back to the original Flight Simulator, which was known for being very ill-behaved, talking directly to hardware. They recalled the old adage – "if you can't run Flight Simulator, you ain't PC compatible".

After pondering for months, the engineering team realized that using stock motherboards and chipsets was not a good idea, given all they've read in Loyd Case's stories at ExtremeTech about problems he's experienced in compatibility and stability with numerous new chipsets and motherboards over the past few years. They knew that chipsets were continually integrating more complex functionality with each successive generation, and this provided far more potential for system failures. Intel, VIA, SiS, Nvidia – they all have chipset issues. So instead of using highly integrated chipsets, AT&T chose to fall back to the discrete, reliable and proven component approach.

Below is a picture of the latest PC 6300 Plus+ motherboard (eerily similar to the original 1985 pre-production Gen 4 PC 6300 Plus motherboard) with 185 large discrete components. This motherboard mounts on the bottomside of a desktop unit, facing downward, and the connectors on the left edge slip into the u-turn bridging connector (shaped like a horseshoe) mentioned earlier, and it attaches to the bus expansion card with mutiple slots that sits in the main chassis (more on that later).

The first things you'll note are the engineering change wires running all over the board. Often called "white wires", AT&T purposefully added the wires to show users just how customizable this board can be. They'll provide circuit schematics, a set of 100 white wires, a soldering iron, a book called "The Joy of Hand-Routing Motherboard Signals", and another called "Cuts and Traces 101" with each system.

We applaud AT&T's desire to not increase board dimensions when adding more circuits. Instead, they added a daughter board (you can see the words "daughter brd" are inscribed on the separate little board sitting atop the big board). We do question the reliability of the daughterboard attachment, because we know that many shook loose during transport and handling back in the mid-80s on the original PC 6300 Plus. Today's engineering team assures us the boards have a new formulation of a liquid nail-like compound that withstands high degrees of shock and vibration.

Processor choice on the new PC 6300 Plus+ was difficult decision, and we think the AT&T execs may have been a bit too literal when describing application compatibility requirements to their engineers (being able to run even the most challenging original IBM PC software), but we understand their intentions.

The execs knew that ever since the 80386 was introduced back in 1985, a whole bunch of Protected Mode virtual machine managers and Protected Mode OSs were built, and they spawned the creation of a bunch of bloated and error-laden MS-like operating system and application software. So, the processor choice was obvious to avoid such malware on the PC 6300 Plus+ -- the 80286, and we agree with their decision. Note that the CPU is located under the heatsink in the board photo.

Avoiding the new, unstable chipsets allowed the engineers to implement more reliable discrete components such as interrupt and DMA controllers. In fact, AT&T chose to limit the design to only a single 8237A DMA controller and a single 8259A interrupt controller, without cascading to second controllers of each type, which helps reduce the number of problematic interrupt-driven ISA cards that can be installed in the system. And fewer expansion boards means less bus loading, less electrical interference, etc. PCI interrupt sharing has always been troublesome, so they won't go there either.

Memory? Simple. Put 1MB of unfailing 256Kbit chips (36 of them with parity) down on the motherboard. The rationale being that 1MB was good enough to hold a bootable and usable kernel of AT&T Unix System V in 1985 (with a wee bit of swapping), so AT&T will make it good enough for their new pared-down version of Linux. If you want to add more memory you can, using three 2MB memory boards, for a total of 7MB as in the original PC 6300 Plus. The bottom line is that you have assurance that numerous bloated-software-driven problems cannot happen in this design. Heck, most virus code probably needs more memory than that, so the systems are more secure too. The PC 6300 Plus+ maintains "0" wait-state memory operation at 6MHz (which is actually faster than the IBM PC/AT's 8MHz system with one memory wait-state).

The new memory boards are near identical in style to the original PC 6300 Plus memory board pictured below, with 72 discrete 256Kbit memory chips. The original board was built for AT&T by AST Research, and it provided AST Rampage/AT functionality using AT&T's funky PC/XT compatible bus (that had a 16-bit extension-slot that was not compatible with the PC/AT "ISA" 16-bit bus). Note the "Attila" markings on this very first board out of the AST Research factory back in 1986, which was supposed to designate AT&T's conquering the PC market. Of course the Attila markings never made it to the public, as that would have been so unlike AT&T at the time (especially just coming out of monopoly mode).

Hard drives? Easy. The less data that can be stored, the less chances of trouble. AT&T execs were going to choose the 20MB Seagate ST-225, but instead opted for a bit more modern 40MB ST-251-1 as pictured below. The 251-1 has 28ms access time instead of the slower 40ms ST-251. I believe it has a 1:1 interleave factor too. A great choice.

AT&T plans a worldwide launch of the PC 6300 Plus+ at the end of April, priced 15% below Dell P4 Canterwood-based systems, whenever they ship. We think the PC 6300 Plus+ shows great promise.

Oh, and here's a photo of two technical product managers for the AT&T 6300 Plus+. The guy on the left is Rick Edwards, and we're not sure who the guy on the right is, but it looks a lot like this author circa 1985 (age 30).

Copyright © 2004 Ziff Davis Media Inc. All Rights Reserved. Originally appearing in ExtremeTech.





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