Electro What?

A popular myth that explains how Alpha chips got the nickname EV describes how engineers decided during lunch one day to excite a pickle to the frequencies at which Alpha chips run. The engineers plugged the pickle in to a pair of electrodes. The pickle glowed green, and from then on Alphas had the nickname Electro Vlasic, or EV for short.

Unfortunately, the truth isn't so amusing. Digital's original plan
for the Alpha processor, even before it had the name Alpha, was to replace the company's venerable CISC architecture, the VAX. Digital planned to provide an extension to the VAX family that would carry the product line into the next century. Some Digital employees took advantage of this opportunity to create a processor with no historical baggage or hardware emulation, and after the project was partially finished, Digital scrapped the Extended VAX (EV) plan and began to design a new chip. The only portions of the original project that the new chip retained are VAX floating-point compatibility (which is available in addition to the standard Institute of Electrical and Electronics Engineers--IEEE--floating-point format) and the EV designation.

The first number that follows EV in Alpha chips' designations identifies the processors' generation. (I haven't heard Digital's solution to the nomenclature of processors beyond the Alpha's ninth generation.) If a second digit appears after EV in a processor's name, it denotes that the chip has a more advanced process technology than the first chip of that Alpha generation. Table A shows the Alpha's processor designs and corresponding process technologies.

TABLE A: Alpha Processors and Features
Designation Processor Process Technology (microns) Speed Range (MHz) Special Features
LCA4 21066 0.75 166 Low-cost Alpha (LCA)
LCA4S 21068 0.75 >66
LCA45 21066a 0.50 233
EV4 21064 0.75 100 to 200 Original dual-issue Alpha
EV45 21064a 0.50 225 to 300 Level 1 cache doubled
EV5 21164 0.50 250 to 366 Quad-issue
EV56 21164* 0.35 400 to 767 Byte and word instruction alignment
PCA56 21164PC 0.35 400 to 600 Level 2 cache removed; motion video instructions (MVI) added
PCA57 21164PCa 0.25 667 Announced in February 1998; not available at press time
EV6 21264 0.35 450 to 600 Hex issue, speculation, and branch prediction
EV67 21264a 0.25 800
EV68 21264b 0.18 1000
EV7 21364 0.25 1200 On-chip cross-bar switching
EV8 21464 0.18   On-chip Symmetric Multiprocessing (SMP)?
* Digital originally planned to call this processor the 21164a, but the company dropped the a from the processor's name. Many users still refer to this processor as the 21164a.
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