Re: Short Vectors Versus Long Vectors

On Tue, 23 Apr 2024 19:25:22 -0600, John Savard wrote:

After all, the reason the Cray I succeeded where the STAR-100 failed was
that it had those big vector registers ...

Looking at an old Cray-1 manual, it mentions, among other things, sixty
four 64-bit intermediate scalar “T” registers, and eight 64-element vector
“V” registers of 64 bits per element. That’s a lot of registers.

RISC-V has nothing like this, as far as I can tell. Right at the top of
the spec I linked earlier, it says:

    The vector extension adds 32 architectural vector registers,
    v0-v31 to the base scalar RISC-V ISA.

    Each vector register has a fixed VLEN bits of state.

So, no “big vector registers” that I can see? It says that VLEN must be a
power of two no bigger than 2**16, which does sound like a lot, but then
the example they give only has VLEN = 128.