Alpha/Linux Wiki

Wikipedia has articles on the Alpha architecture and on the 21064, 21164, 21264, 21364, and 21464 processors.

See also Chipsets.

Since Linux 6.10, released in July 2024, the kernel requires an EV56 (21164A) or later processor, because it needs the byte/word extension (BWX) to make byte and word stores atomic. ¹⁾ Current kernels therefore support the EV56 (21164A), the PCA56 and PCA57 (21164PC), all 21264 variants (EV6, EV67, EV68), and the EV7 (21364). The EV4 and EV45 (21064 and 21064A), the LCA4 and LCA45 (21066, 21066A, 21068, and 21068A), and the EV5 (21164) need Linux 6.9 or earlier.

Distribution userlands have their own baseline. Debian's GCC has generated EV56 code by default since May 2023, ²⁾ so Debian packages need at least a 21164A. Gentoo's Alpha profile sets no -mcpu, so its stages use the compiler's default, the architecture baseline. ³⁾ See Toolchains: Distribution baselines.

The consoles report processors by part number rather than by EV name, for example "Alpha 21264A-8 666 MHz" on a DS20E, so the EV name has to be looked up from the part number. ⁴⁾ The table maps the processor type codes in Tru64 UNIX's cpuconf.h to part numbers and EV names, ⁵⁾ with the LCA4 and EV7 codes from the kernel's hwrpb.h, ⁶⁾ and gives the GCC -mcpu value for each. GCC has no separate value for the LCA4, which uses ev4, for the EV68 and EV7, which add no instructions to the EV67, or for the PCA57, which uses pca56. ⁷⁾

The Extensions column lists the optional instruction set extensions that GCC enables for each -mcpu value. ⁸⁾ BWX is the byte/word extension (ldbu, ldwu, stb, stw, sextb, sextw), FIX the square-root and floating-point convert extension, CIX the count extension (ctlz, ctpop, cttz), and MVI the multimedia extension. ⁹⁾ Code built for a processor with more extensions does not run on one with fewer; see Toolchains: Selecting a processor and Distribution baselines for the -mcpu that distributions build with, and amask for checking a running processor.

The Samsung part numbers are from Samsung's AlphaPC 164UX/BX manual. ¹⁰⁾

Compaq sold the DS20 and DS20E CPU modules as options KN310 (500 MHz), KN311 (667 MHz), and KN312 (833 MHz). The suffix of the option number gives the operating system the option was sold for: -xB for Tru64 UNIX, -xC for OpenVMS, and -xD for Linux. The table lists the Compaq modules; the AlphaPC 264DP's own 500 MHz daughtercard (21A06-M0) has 2 MiB of cache. ¹¹⁾

On earlier revisions of the 500 MHz modules the second CPU of a dual system could disappear after a power cycle; the revision notes are from Compaq's Information Blitz TD 2690. ¹²⁾ See Goldrush.

Alpha has no integer divide instruction; division is a library routine, so division-heavy code runs slowly. ¹³⁾

The 21164 was announced on 7 September 1994 in 266 MHz and 300 MHz versions, as the first Alpha with two levels of on-chip cache. ^{14) 15)} Faster parts followed, reaching 600 MHz from Digital on 31 March 1997, alongside the ATX form factor AlphaPC 164LX motherboard; Samsung later sold 633 MHz and 667 MHz parts. ¹⁶⁾