BYTE June 1993 on page 80
Cover Story
Tom R. Halfhill
Mips Technologies (Mountain View, CA), a relatively small chip-design house owned by Silicon Graphics, hopes Windows NT will enable its highly regarded RISC processors to challenge Intel's decade-long grip on the mass market for PCs. Raw speed isn't a problem for Mips processors. The clock-doubled 50-/100-MHz R4000, which costs about the same as a 33-MHz Intel 486 (around $400 in 1000-piece quantities), runs two to four times as fast. The 75-/150-MHz R4400, scheduled for volume production in June, costs about the same as a 66-MHz Pentium (less than $1000) and runs about twice as fast as Intel's flagship processor.
Today, Mips's processors are a trickle in the torrent of 80x86-compatible chips entering the PC market every year. Intel's high-volume manufacturing facilities ensure a healthy supply of chips, and its competitors (AMD and Cyrix) help keep prices in check. Mips has responded by licensing production of the R4000 series to six independent suppliers: Integrated Device Technology, LSI Logic, NEC Electronics, Performance Semiconductor, Siemens Components, and Toshiba.
Even if Mips can get supply and price under control, it's going to be hard to convince PC clone makers that a RISC PC is viable. Designing new systems around high-speed RISC chips is a daunting task. Many PC vendors weakened by last year's price wars can no longer afford major R&D efforts.
To seed the development of R4000-based systems, Mips recently founded the ODC (Open Design Center) in Mountain View. The ODC sells design kits that enable cloners to jump from using an 80x86 to using the R4000. One kit includes a reference motherboard for building systems specifically tuned to Mips processors; another has an under-$20 pair of ASICs (application-specific ICs) that allow vendors to adapt the R4000 to existing 486 motherboards. Either way, just add memory, peripherals, and Windows NT, and you've got a complete R4000 system that Mips suggests will be a Pentium killer.
One of the ODC's first customers is Carrera Computers, a
start-up company in Laguna Hills, California. In February, Carrera began selling
R4000 motherboards based on one of the ODC's reference designs. Sized to fit
standard AT cases and intended for high-performance workstations or servers, the
$4995 board includes a 1280- by 1024-pixel local-bus video controller, 2MB of
VRAM (video RAM), SIMM slots for memory expansion to 256 MB, four EISA slots, a
SCSI-2 connection, an Ethernet port, parallel and serial ports, and
PS/2-standard keyboard and mouse ports.
Carrera founder and chairman Bruce Faust believes that PC vendors will adopt RISC because it is economically sound and technically painless. While Carrera's motherboard complies with the ARC (Advanced RISC Computing) specification, he says that in the long run "ARC won't matter a hill of beans." ARC features, such as an EISA bus, SCSI, and built-in networking, can be omitted from the kind of bare-bones boxes that PC clone vendors like to sell. In fact, Carrera is working on a lower-priced R4000 motherboard that does just that. Faust claims that by the end of this year you'll be able to buy a $3500 RISC PC that delivers four times the performance of a 66-MHz 486DX2.
Ronald Chwang, CEO of Acer America (San Jose, CA), makes a similar claim. Acer, however, is taking a very different approach. Rather than adopting a Mips reference design, the company has developed a new system architecture called PICA (Performance-Enhanced I/O and CPU Architecture). "As CPU power continues to increase," says Chwang, "you must innovate to bring I/O bandwidth into balance with it. NT encourages us to do that."
At the core of Acer's minicomputer-like design is a 64-bit, 200-MBps bus connecting the R4000, memory, video, and a 64-bit, four-channel I/O processor that gives each channel independent DMA and bus-mastering capability. Integral Ethernet and SCSI I/O attached to those channels goes faster than it would on an EISA bus, and the design eliminates the prohibitive cost of EISA bus-mastering logic. A standard AT-bus controller does, however, support ISA cards.
PICA chip sets and motherboards not only will be found in Acer systems, but also will be licensed to other vendors through the ODC. A typical configuration may include a 50-/100-MHz R4000 chip, 16 MB of RAM, a 200-MB SCSI hard drive, a CD-ROM drive, a floppy drive, an accelerated video card on the video bus, built-in Ethernet, and a SCSI-2 port. The cost of such a configuration will be around $3500 (not including monitor).
PICA will compete with another new post-AT architecture--Intel's PCI (Peripheral Component Interconnect). Not simply a rival to the VL-Bus local-bus standard, PCI is actually a sweeping next-generation system architecture that just happens to support ISA and EISA for backward compatibility with old expansion boards. Like Acer, Intel offers a complete chip set that makes it easier for PC vendors to implement the new architecture; like Mips and the ODC, Intel is offering a reference motherboard that anyone can copy or modify.
A significant difference between PCI and PICA is that Intel's PCI supports any microprocessor, even non-80x86 and non-Intel chips. The current version of Acer's PICA works only with the Mips R4000 series, although Acer says future versions could support other chips as well. What PCI and PICA have in common is high performance, backward compatibility with the familiar AT bus, and a balanced approach to system architecture.
Windows NT is shaping up as the battleground not only for next-generation microprocessors, but also for next-generation PC system architectures.
Photograph: The PICA Mips motherboard.
Photograph: The ODC/Carrera Mips reference-design motherboard.
Tom R. Halfhill is a BYTE senior news editor. You can reach him on BIX as "thalfhill.