IBM's NEXT GENERATION Two of the really nice touches are The IBM PC-AT had claims made for it on its release that the two-speed, temperature-controlled it not only harnessed the most advanced technology cooling fan and the lock. The new T') fan makes this system a lot quieter (hence the :A but also surpassed the original PC in than any other member of the PC both power and speed (not hard...). Since then there's family, and in many office situations been a fair bit of controversy about how good the AT that can be a real blessing. When locked the PC-AT can be switched is, and claims that it's suffering from too many bugs to on but not used. The operating be commercially useful. Lloyd Borrett took a look one system won't boot, and the cover of the new machines. can't be removed . Once you're up i and running, locking the system makes the keyboard inoperative. On August 14 1984, three years after were the 16-bit support chips Yes, I know .these are but little frilly the introduction of the first IBM required. The chips necessary to bits to many of you, but to those , 113M US released build an 8-bit bus system based on who use a computer for extended the Personal Computer AT (for the 8088 were not only available, periods in the typical office environment Advanced Technology). The PC-AT is but a lot cheaper. The real criticism they are quite important. an -based here is that IBM should have released that dwarfs the original PC in compu­ an 8086 or 80186-based system The Meat in the AT tational speed and power. twelve to eighteen months ago when Okay, let's get to the meat of it. The But not only did IBM release this the market was ready for it. Its PC-AT comes as two models. The new-generation microcomputer, it also opposition did. base model gets one half-height 1.2M announced three new operating Well, IBM has answered the diskette drive and 256K of memory, systems (PC-DOS 3.0, PC-DOS 3.10 opposition by leaping ahead to an while the up-market one gets an and XENIX), a Intel 80286-based system, the PC-AT. additional full-height 20M fixed disk (PC Network), and a windowing Forget that IBM says you can only drive, serial and parallel ports, and a environment (Topview). In the months have three megabytes of memory, total of 512K of memory. since August there have been more because the 80286 chip can address Disk storage can be further extended announcements: Virtual Device 16M of memory, and AST Research by adding a second 20M fixed disk Interface, Enhanced Graphics Board, has already announced a multi-function drive, or your choice of a second and Professional Graphics Controller board with 256K, expandable to 3M. 1.2M diske~e drive or a half-height are just a few. In fact, running in its native mode the 320/360K diskette drive. (There is That is a lot for the industry to 80286 can support four tasks, each every chance that someone will come about. To this day the sages of of which can use one gigabyte of up with a way to add a half-height the microcomputer world are still virtual memory; the chip has all the 20M fixed disk drive when two half­ trying to assimilate it all, but let me instructions necessary to perform the height diskette drives are already in­ give you my brief version of what it required . But stalled .) all means. I'll start from scratch with let's come back to earth. This next bit isn't as confusing as the IBM PC-AT. it may first sound : you can use the The Frilly Bits 1.2M diskette drive to read and write IBM Listened The keyboard has been changed! to 1.2M diskettes with the 1.2M This is one very fast, well thought-out Shock, horror! As a two-finger-and­ format, but you can't read these machine. I've had one since early thumbs typist, I actually liked the old diskettes in eXisting 320/360K diskette November and I'm impressed. IBM keyboard. Quite a few people expressed drives. Well, you'd expect that, has listened to many of the criticisms other opinions, and IBM changed it. wouldn't you? But get this. You can levelled at the original PC and done With over two years pecking out use1.2M diskette drives to read and something about them. letters on the old keyboard the new write to 320/360K diskettes with the A lot of people thought the original one takes a little getting used to, but 320/360K format. Now for the catch. PC should have been based on the it is better. So there are now three Once a 1.2M diskette drive has chip instead of the 8088. keyboard layouts in use within the written on a 320/360K diskette, that Actually I thought it was a wise move IBM's Personal Computer family: on diskette can't be read in a 320/360K at the time; the 8086 wasn't readily the original PC, the 3270/PC, and the diskette drive. available, and more importantly nor PC-AT. As the PC-AT I'm using doesn't yet 20 base memory. To get 640K of base SYSTEM UNIT memory, as in the PC and PC-XT, an additional 16-bit bus 128K memory must be purchased. SYSTEM BOARD The 512K memory 16-bit bus memory 80286 80287 Oscillator H Power Supply expansion cards available from IBM Co-processor 115/230 go into the area above the one megabyte limit of an Speaker 16 ROM Speaker H . Extended memory will be ' , Connector Levels fully exploited by XENIX when it 7 Channel RAM Keyboard H Keyboard becomes available. PC-DOS 3.x can DMA Controller J only use it as a RAM disk. There are eight full-length expansion CMOS Real-Time Battery H Battery slots in the PC-AT. Six support both Clock Connector the old 8-bit and the new 16-bit bus, two support only the 8-bit bus. Some of the current option boards can only Fixed Diskette be used in the two 8-bit bus slots, Disk Drives while others can't be used at all. The Drives IBM colour graphics adapter board is ~~,"",I ~~~~~~~~ an example of one that must be in the 8-bit bus only slots. Fixed Disk and The new combination parallel and Diskette Adapter serial adaptor uses the same 25-pin 00000 0 connector for the , but a 9-pin connector for the ! If only they were the other way round! Monochrome Display and Monochrome Display I'll rarely use that parallel port, but Printer Adapter ' now I've got to get special communi­ Graphics Printer cations cables made up for the serial Serial/parallel Color Printer port. Adapter The PC-AT uses a CMOS RAM and a rechargeable battery to store Color/Graphics , the hardware configuration, instead of Monitor Adapter Color Monitor switches on the . This saves having to open up the box and Prototype RF Modulator reset switches when different combi­ Adapter nations are being tested. Believe me, there are times when you really wish 128KB Memory you didn't have to keep taking the Expansion cover off and putting it back on. The battery also keeps the built-in calendar 512KB Memory clock going. Exppnsion The Game Control Joysticks Now for the really important stuff, the Adapter software. To use the PC-AT, PC-DOS ~ Synchronous Data Link Control Adapter

Binary Synchronous Communications Adapter

System diagram of the AT.

have a 320/360K diskette drive, and I like to move my work around between the various systems based on availability, that often eliminates the PC-AT from contention. Think carefully as to whether you should add a 3201 360K diskette drive if buying a PC­ AT; I would be very hesitant about adding a second 1.2M diskette drive. The 512K of memory available on the motherboard is referred to as 21 TYPE OF PO.,WER BATIERY KEYBOARD DISPLAY SUPPLY REAR PANEL CONNECTOR CONNECTOR SWITCH CONNECTORS

...Jcn weI: Z~ Zu

80286

RAM JUMPER SPEAKER CONNECTOR

The AT's system board.

3.0 is required. It has the changes most is the ability to use the COUN­ aren't really worth the additional necessary to support the new 1.2M TRY = option in the CONFIG.SYS file expenditure. Okay, you would get a diskette drive, the 20M fixed disk to specify Australia. Most of the DOS few nflw features, but it also uses drive, the calendar clock, and so on . commands then display the time and more memory. Wait, and buy DOS There are a few nice additions to date in our format instead of the 3.10 Wl1en you want PC Network DOS 3.0, such as an IBM-supported usual US format. support !ater on. RAMDISK driver, a change volume If you're an existing user of DOS labels command, and an enhanced 2.0 or 2.10, I wouldn't rush out and Incompatibility? print command. The one I like the buy DOS 3.0; the few extra nice bits Currently there is one big problem 24 with the PC-AT: not all the existing PC software will run on it. In fact quite a fair amount of it won't. But, in IBM the words on the cover of that infamous book, DON'T PANIC. This is a problem that has been coming for a long time. When a examples include Framework, dBase for PCs and true PC compatibles, not manufacturer provides the programmer III and Symphony. But what's the bet for other . Fourth, it's with an to access these programs will still bypass the not supported by XENIX. Finally, it's the hardware, it is expected that the DOS interface? That means they are IBM's own interface. programmer will usa the interface likely to get caught again real soon. PC Network is not IBM's planned defined by the operating system. But One good thing programs bypassing overall token-passing network. It is a there are always programmers who the DOS interface do is provide -based PC network specific­ are smarter than that, and for various compatibility tests. Programs such as ally designed to interconnect personal reasons decide to bypass the operating 's Flight Simulator and the computers. IBM has promised there system. In the case of the PC they Norton Utilities have been used by will be a gateway between the PC either use the BIOS code in ROM on reviewers as the classic test as to Network and the token-ring, cabling the motherboard, or go direct to the how compatible XYZ's new lookalike system-based network, and IBM has hardware itself. really is. These same reviewers have traditionally made good on such These programmers can always used the fact that such programs promises. justify why they do this. Strangely have problems running on the PC-AT The broadband-based IBM PC enough, they are also the first to to write nice sensational stories about Network was mostly built by Sytek, a complain when the manufacturer how incompatible the PC-AT is. Californian LAN speCialist, but changes the rules, and their software Apparently there have been problems significant parts of the network's stops working. In the PC-AT, IBM with the 20M fixed disk drives on a design are IBM's. has made some significant hardware few PC-ATs in the US, and that too The board components are separated changes, and also changes to the makes great copy. Because IBM has by the logical function they perform, ROM on the motherboard. Result such a long-standing reputation for roughly along the lines specified for scratch quite a few programs. not having such problems, any that the different layers of the open In most cases the reason the surface are given wide coverage. At systems interconnection (OSI) model programs no longer work is that they the same time, some rather fundamental now being defined within the Interna­ are doing direct ROM BIOS and problems with other systems are quite tional Standards Organisation (ISO). hardware calls in order to implement often glossed over. I know a number By replacing the coaxial-cable elec­ various copy protection mechanisms. of other userS of the PC-AT in tronics with circuitry for twisted-pair The 1.2M diskette drive and 20M Australia, and only one has had a interface, and CSMAlCD control with fixed disk drive required some major problem - a faulty memory chip. token-passing, a similar board could changes that have brought such accommodate IBM's proposed token­ programs unstuck. Those of you who It's Fast ring network. already know my opinion of copy Okay, I've already said the PC-AT is It is significant that only layers protection mechanisms will understand fast, and those who have used it three to five of the OSI model how this is giving me a warm feeling would certainly agree. But how fast is (network, transport and session inside. I try to avoid programs that it? levels) are Sytek-developed. While the are protected, or can't be unprotected Well, all the benchmark tests I've network is open to software developers, - all the programs I have in day-to-day done indicate that the AT outperforms the communications protocol embedded use run on the PC-AT. the XT and PC by three to one on in layers three to five is the property New 'fixed' versions of most memory or calculation-intensive tasks. of Sytek. Sytek technicians say there programs that don't currently run on A specific example is a Lotus 1-2-3 is no way anyone can build an the PC-AT are in the pipeline; spreadsheet that took 300 seconds to interface card to the PC network recalculate on the XT and only 110 without a licence to use that protocol seconds on the AT. or the IBM PC Network board itself. APPLICATION LAYER When comparing the I/O performance The all-important layer seven (user/ of the 20M fixed disk drive on the device/application interface level) is AT against the 10M fixed disk drive implemented via an 8K Network Basic PRESENTATION LAYER on the XT, the ratio is two to one. A Input/Output System (NETBIOS) ROM read/write test of 5000 random which IBM defined. So be wary of SESSION LAYER records took 415 seconds to finish on the recent Sytek advertisements the XT and 190 seconds on the AT. which claim buying their product now TRANSPORT LAYER is the same as buying IBM's PC IBM's Local Area Network Network. I believe the most significant parts of IBM's PC Network is obviously NETWORK LAYER the August announcements are PC aimed at its large competitors. Going Network and DOS 3.10. The network with or some de facto DATA LINK LAYER is an important strategic move for standard would have aided Xerox or IBM, notable for what it does and another large vendor, so IBM chose PHYSICAL LAYER doesn't do. First, it's not Ethernet. to go its own way. It's not hard to Second, it's not compatible with any guess they're hoping PC Network will become the new de facto standard. The ISO System Interconnection Model. of the other major contenders for the network crown. Third, it's a network What does this mean? Well, finally ~

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