On Thu, 7 Aug 2025 at 23:26, Maciej W. Rozycki via cctalk <[email protected]> wrote: > > On Thu, 7 Aug 2025, Paul Koning wrote: > > > > Well, the very same year MIPS Computer Systems came up with the R2000, a > > > classic RISC design, featuring a(n almost) non-interlocked pipeline design > > > and with the same 4GiB paged virtual addressing capability and memory > > > protection also giving true multitasking. A processor architecture the > > > descendants of which live in millions of devices around the world, and > > > which inspired other architectures such as DEC Alpha or more recently > > > RISC-V. > > > > I believe the ancestry of Alpha is a bit different, given that it was > > DEC's third generation RISC design, after the R&D one-off Titan (1982, > > see https://bitsavers.org/pdf/dec/tech_reports/WRL-86-1.pdf) and the > > canceled PRISM (spring 1985, > > https://bitsavers.org/pdf/dec/prism/memos/850528_NONVAX.pdf which > > mentions Titan and Berkeley but not MIPS as inspiration). > > Well, the similarity of the ISA is striking, unlike with say the ARM or > POWER ISAs, and the timeline and the use of MIPS processors in DEC systems > makes it hard to believe there was no influence. That does not preclude > other inspirations and it's worth noting that a key architectural mistake > was avoided (learnt from?), that is the lack of pipeline interlocking.
Given that DEC shipped their first MIPS based DECstations in 1989, and PRISM was (I believe) still morphing between 32 bit and 64 bit in that timescale, it seems very likely that the engineers working on Alpha were not only aware of MIPS but had direct experience of DEC hardware and software running on MIPS... Ancestry... arguable, influence... more than likely :) David
