With last week’s announcement from Chips & Technologies Inc and partners (CI No 850), the race is on with Western Digital Corp to become the progenitor of the first clones of IBM’s Personal System/2 – if anyone is courageous enough to brave being the first recipient of a lawsuit from IBM. And whoever does come out with the first clone does look likely to get the rough side of IBM’s lawyers – company after company is saying that it has approached IBM for licences and has not got any satisfaction, although officially talks are still on-going and there’s no word of IBM actually showing anyone the door. Vacant space Chips & Technologies says that its first products, the Chips/250 seven chip set for building PS/2 50 and 60 clones will be sampling in February. The set enables a clone to be built with 68 devices, 51 fewer than IBM uses on its highly integrated motherboard; the vacant space can be used by designers to add features that differentiate their machines from the competition. Samples of the Chips/280, also a seven chip set, for cloning the Model 80, will be available in February. The company says that the set will enable OEM customers to build machines that outperform IBM’s offering, using just 75 devices where IBM is at present using 192. Chips is also promising a higher performance Chips/281 set in the second quarter, which will add a cache and enable machines to be built that walk all over the Model 80. Indeed higher performance was regarded as an equal goal to 100% compatibility with the Micro Channel when the company handed the assignment to its engineers. The sets meet fully the Micro Channel timing specifications, and Chips says that thet are compatible with all IBM’s hidden registers and functional modes, and will boot up in IBM-compatible mode. They have been tested with IBM’s BIOS, its OS/2 Extended Edition and Presentation Manager, MS-DOS and Xenix, for compatibility. On the performance front, Chips believes that outdoing the PS/2s is vital because the size and overhead of OS/2 is so enormous that the IBM machines are likely to grind to a halt when really put through their paces. Chips & Technologies has a matched memory feature in the Chips/250 set so that clones of the Model 50 and 60 can run faster than IBM’s 10MHz while retaining compatibility. Clones will be able to run at 10MHz, 16MHz or 20MHz, a capability not built into the originals. Model 80 clones will be able to operate at up to 25MHz. Designers will also be able to use cheaper 100nS access memory chips at 16MHz with 0.5 to 0.7 wait states where IBM uses its own 80nS, 16MHz, one-wait-state parts which are more costly on the open market. The seven chips in the Chips/280 set are a processor-Micro Channel controller; advanced memory controller, advanced direct memory access controller, data address buffers, system peripherals controller, multifunction controller, and the hard disk controller set which is coming from Adaptec. On the Micro Channel front, Chips & Technologies reckons it has made several enhancements. The matched memory implementation accesses memory 33% faster than does IBM’s implementation, and the tightly coupled Fast VGA cycle is claimed to cut input-output and memory cycles by 50%. On the OS/2 front, some of its functions have been hardwired to reduce the overhead a little. Among the functions implemented in microcode is fast CPU reset that minimises the delay when the processor has to switch from protected to real mode to use the MS-DOS utilities that are required by OS/2. And a function called a fast gate A20 prevents MS-DOS from accessing memory over 1Mb when switching from protected to real mode. OS/2 functions The OS/2 save and restore of graphics in a multitasking environment is also microcoded. The Lotus-Intel-Microsoft 4.0 expanded memory feature is implemented for memory above 1Mb, and it will support up to 16Mb in four banks of 4Mb. On the Chips/250 set, the company claims that clones of the Model 50 and 60 could run at up to 20MHz, use up to 8Mb of memory, and provide better graphics than do IBM’s PS/2 machines. The
set needs only 200nS 10MHz memory chips where IBM uses 120nS 10MHz parts. The 16-bit set consists of seven parts, each with the same functionality as the Chips/280 parts. And again, some OS/2 functions are in silicon. The company says that its new Video Graphics Array chips, the Chips/450 series, can be used to build VGA boards for standard MS-DOS micros as well as PS/2s. There are currently two alternative parts, the VGA Controller and the Super VGA Controller. Chips & Technologies claims that the proprietary interface is up to 50% faster than IBM’s VGA, while the 16-bit data path, intelligent processor arbitration, and page-mode memory cycles are each twice as fast as IBM’s implementations. The chips have a dual bus architecture, take advantage of many undocumented VGA features, support high resolution, and panning in up to a 1,024 by 1,024 bit-map resolution, and are backwards compatible with EGA, CGA, MDA, and Hercules graphics. The Super version supports an external palette of up to 16m colours and resolutions of up to 640 by 480 pixels in colour, and 1,280 by 960 in monochrome. They are also designed to work with IBM’s OS/2 Presentation Manager and Microsoft Windows/386 without the need for special drivers. The VGA Controller provides 1,024 by 768 pixel resolution in monochrome. The Super VGA Controller is a superset of VGA graphics modes, and 1Mb of display memory. A hardware graphics cursor is said to reduce cursor overhead by 95%. Disk controllers Phoenix Technologies has a PS/2 BIOS, and Adaptec steps to the fore on the disk controller front. The Milpitas firm has developed MFM and RLL controllers for clones of the 50 and 60, and an ESDI controller and SCSI adaptor for Model 80 or 60 clones. The ACB-2610 MFM controller supports two drives and operates at direct memory access burst speeds of up to 10MBbtes per-second. Buffers of 8Kb, 32Kb and 64Kb are supported. The ACB-2670 RLL controller supports two drives of up to 285Mb each, and transfers data at 7.5Mbytes-per-second with a 10Mbps burst rate. The ACB-26M20 is a multitasking ESDI disk controller that supports multitasking and multithreading, executing three tasks simultaneously. It again supports two drives with up to 780Mb all told, and like the other parts supports optional data buffers, read-ahead cache, and error correction. And the AHA 1640 SCSI host adaptor is described as a full synchronous, multitasking device. It supports up to 56 drives and can handle up to 255 simultaneous tasks with an input-output bandwidth of 5Mbytes-per-second and a host bandwidth of 8Mbytes-per-second. According to Adaptec, it will also support optical disk drives, scanners, local networks and printers. So all the parts are in place for cheap and simple cloning of the PS/2 family – well all except the 80386 still in short supply. But will any major think the PS/2 worth cloning at this stage in the game?