RISC-Based Mainboard Advancements

Right now, there are three RISC platforms that offer standard PCI-based desktop mainboards on the open market: Alpha running Windows NT, PowerPC running Mac OS, and Sparc running Solaris (for Sun UltraAX boards only, using the UltraSparc II CPU).

For the PC market, Alpha is now the only RISC Windows platform, and its three CPU suppliers (Digital Semiconductor, Mitsubishi, and Samsung) are strongly driving the push into the mainstream with a new series of Alpha mainboards in standard ATX, which are set to come out this year. For the standard midrange 21164 processor at frequencies up to 600 MHz (800 MHz if supercooling is used), the PC164LX mainboards from Digital are available with 2 MB of 128-bit burst cache, as well as a 128-bit, 66-MHz SDRAM main memory bus with four DIMMs, providing up to 512 MB of RAM.

The new mainstream 21164PC processor runs at frequencies up to 533 MHz and is supported by the PC164SX mainboard, which is similar to the LX but with only 1 MB of burst cache. Both boards use the 21174 Pyxis chip set, integrating the whole North Bridge core logic with a 64-bit PCI interface in a single BGA chip. The mainboard designer can then choose from a variety of South Bridge chips from Cypress, Intel, VIA, or VLSI Technology. While the LX uses the Intel 82378ZB bridge, the SX uses the new Cypress bridge, which provides USB functionality. Importantly, Digital Semiconductor offers design information on these reference mainboards to mainboard makers interested in embracing the Alpha.

VLSI Technology offers the new Polaris single-chip North Bridge for the 21164PC Alpha, providing even tighter integration and saving a lot of external discrete logic. The PC164ZX mainboard from Digital, similar in specs to the PC164SX, will use the Polaris. Several mainboards from other Alpha manufacturers are also expected to use Pyxis or Polaris chip sets for the 21164 generation. In fact, the new PCA 57 0.25-micron successor to the 21164PC, expected to arrive around year's end, will be supported by the AGP-capable Polaris 2 chip set. The PCA 57, expected to be produced by all three Alpha CPU vendors, should reach 800 MHz in desktop versions and 600 MHz in low-voltage notebook versions. With its dual-CPU support, ultrafast cache and memory buses, and very small die size, the PCA 57 will be a fantastic competitor to Intel's 350- to-400-MHz Deschutes.

On the high end, the 21264 EV 6, running at 600 MHz and higher, should be supported around year's end by a series of reference mainboards: the PC264 uniprocessor, the PC264DP dual processor, and, later, the PC264QP quad processor. All are based on configurations of the Tsunami 21272 chip set in either integrated or modular configurations.

With their separate cache and memory paths for each CPU; 6.4-GBps peak total main memory bandwidth from a 512-bit-wide, 100-MHz SDRAM memory; and multiple, parallel 64-bit PCI and AGP buses, these boards should offer the closest one can get to a real supercomputer on a desk, running either Digital Unix or 64-bit Windows NT 5.0. In addition, features such as USB, PC97, UW SCSI, wave-table audio, and Fast Ethernet are expected to appear on some of these boards, with IEEE 1394B Firewire II and 66-MHz, 64-bit PCI 3.0 for1998 revisions. Further speedups will come from the 800-MHz+ 21264 EV67 and 21264PC PCA67 processors in late 1998, as well as the 1-GHz, 100-SPECint95+ 21364 EV7 Alpha in late 1999, which is expected to keep Intel's Merced at bay.

---

Alpha Support at Super Speeds

photo_link (71 Kbytes)

The DeskStation RPX164-2 supports the Alpha 21164 microprocessor at 600 MHz.