The Alpha architecture was 64-bit from the very beginning (though the amount of addressable virtual memory and physical memory depends on the processor implementation).

I think it goes something like:

  - 2106x/EV4: 34-bit physical, 43-bit virtual
  - 21164/EV5: 40-bit physical, 43-bit virtual
  - 21264/EV6: 44-bit physical, 48-bit virtual

The EV6 is a bit quirky as it is 43-bit by default, but can use 48-bits when I_CTL<VA_48> or VA_CTL<VA_48> is set. (the distinction of the registers is for each access type, i.e: instruction fetch versus data load/store)

The 21364/EV7 likely has the same characteristics as EV6, but the hardware reference manual seems to have been lost to time...

In 1998 I somehow got my hands on a DEC OEM 21164 533mhz board for cheap. PCs were nowhere near the performance of that at the time. It mounted in a regular PC case. A friend helped me get the power supply working (there was I think one wire to solder somewhere). Equipped with an ASUS SCSI card, an DEC Ethernet card, and an Elsa GLoria Synergy, it was a full machine. I ran Digital Unix at home on my desk on that for quite a few years. Wish I had kept it for old times sake.

One thing I remember about Alpha though was how bad the output from gcc was. Then DEC released a version of their own compilers that was command line compatible with gcc. That changed everything for open source stuff.

Yeah.

For what we needed, five 32 bit address spaces was enough DRAM. The individual CPU parts were way more than 20% as fast, and the 100Mbit switch was good enough.

(The data basically fit in ram, so network transport time to load a machine was bounded by 4GiB / 8MiB / sec = 500 seconds. Also, the hard disks weren’t much faster than network back then.)