Alpha AXP is a 64-bit RISC processor developed by DEC in 1992. Alpha AXP was used in Alpha systems developed by DEC.
The operating systems that originally support Alpha include
- OpenVMS
- DEC OSF/1, which later became Digital UNIX and then Tru64
- Windows NT
Later also Linux and BSD was added.
Alpha AXP architecture is the successor of DEC VAX architecture. The successor is Itanium.
During the lifetime of Alpha systems many versions of the CPU where developed. The following table presents the CPU versions ordered by the CPU ID.
| Id | EV | Chip | Extensions | Year |
|---|---|---|---|---|
| 1 | EV3 | |||
| 2 | EV4 | 21064 | 1992 | |
| 3 | Simulation | |||
| 4 | LCA | 21066, 21068 | 1993 | |
| 5 | EV5 | 21164 | HWR | 1995 |
| 6 | EV45 | 21064a | 1994 | |
| 7 | EV56 | 21164a | HWR, BWX | 1996 |
| 8 | EV6 | 21264 | HWR, BWX, MVI, FIX | 1998 |
| 9 | PCA56 | 21164PC | HWR, BWX, MVI | 1997 |
| 10 | PCA57 | 21167PC | HWR, BWX, MVI | |
| 11 | EV67 | 21264A | HWR, BWX, MVI, FIX, CIX | 1999 |
| 12 | EV68CB | 21264C | HWR, BWX, MVI, FIX, CIX, PREFETCH | 2001 |
| 13 | EV68A | 21264B | HWR, BWX, MVI, FIX, CIX, PREFETCH | 2001 |
| 14 | EV68CX | 21264D | HWR, BWX, MVI, FIX, CIX, PREFETCH | 2001 |
| 15 | EV7 | 21364 | HWR, BWX, MVI, FIX, CIX, PREFETCH | 2003 |
| 16 | EV79 | 21364xx | HWR, BWX, MVI, FIX, CIX, PREFETCH | 2004 |
| 17 | EV69A | 21264 | HWR, BWX, MVI, FIX, CIX, PREFETCH |
Here the CPU extensions are as follows
- HWR – hardware support for rounding towards infinity.
- BWX – load/store of byte/words
- MVI – multimedia vector instructions
- FIX – Conversions between floating and integer numbers
- CIX – Bit counting instructions
- PREFETCH – support for prefetch with modify intent.
Alpha architecture supports two main floating point number formats: VAX and IEEE. VAX is used for compatibility with the predecessor. Either format can be implemented by the CPU or left for the software emulation.