The new 500MHz Alpha 21164

In early July this year, Digital announced the next level of its high-end Alpha CPUs: 433, 466, and 500MHz versions of the 21164A (revision EV5). These Alpha CPUs are all built from a 0.35µm CMOS process. Subtle changes (over the previous release of the chip) to the pipeline architecture and word addressing scheme enhance performance. The 433MHz chips have been available for a couple of months, and by the time you read this article, Digital will be shipping the 500MHz chips in quantity. The 466MHz version offers systems vendors an opportunity to see how the 500 will perform. The 466MHz chip probably will not show up in many production computers because accommodating the faster CPU is just a matter of changing the clock frequency of the motherboard.

As with the original release of the 21164, this release is still a fully pipelined 64-bit architecture, but with a smaller device size, lower core voltage (2.2V), and higher operating speed­the chip will still dissipate only 22 watts of power at 366MHz. All other characteristics, such as its onboard 96KB Level 2 cache, 8KB/8KB instruction and data Level 1 cache, and superscalar instruction handling (four instructions retired per clock cycle), remain unchanged. The 500MHz chip is the latest in a string of updates over the past nine months that took CPUs from the 266MHz 21064 to the 300MHz, 333MHz, 366MHz, and 400MHz 21164. Figure A shows a functional diagram of the 21164.

The future holds several changes for the Alpha line. Currently, Digital plans to release lower-priced systems based on a new version of the 21064A (such as the 21164PC). Digital will manufacture this system jointly with Mitsubishi and market to a new entry-level graphics PC market. In mid-1997, Digital Semiconductor will release the 21264, an entirely new architecture that will far exceed the performance of the current CPU generation and break the 500MHz speed barrier. Following the 21264, Digital will add motion video instructions to the Alpha architecture to make it a bigger contender in the multimedia market as a high-performance system that won't need any costly peripheral cards. As Digital releases each new generation of chip, the company will drop the price points of the previous versions. Over the next three years, system prices will drop to below $3000.

In the Windows NT Magazine Lab, the new 500MHz 21164 performed at twice the speed of the earlier 300MHz 21164 (EV4). With LightWave 3D on a system with the new DEC AlphaPC 164 Motherboard and running against a Deskstation Raptor 3, the new Alpha chip cut render times in half. With end-user system prices running under $10,000, the new Alpha is a real bargain.

One other thing you can look forward to on the Alpha platform is a 64-bit version of Windows NT (most likely, NT 5.0). Aimed at enterprise applications that need to access extremely large databases, such as applications for credit card companies or airlines, the new 64-bit very large memory (VLM) architecture will support almost any sized database mapped directly into addressable memory. Alpha is an ideal CPU to accommodate this task because it is a true 64-bit engine, instead of a 64-bit chip squeezed onto a 32-bit bus. MS BackOffice will be among the first applications ported to this new environment.