16 Jul
2014
16 Jul
'14
2:53 p.m.
On Wed, Jul 16, 2014 at 02:11:26PM -0600, emanuel stiebler wrote:
On 2014-07-16 12:04, David Riley wrote:
> Making a wild-ass guess, with careful design, you could probably run
> something at least as fast as a KA650 (CVAX) on even a cheap modern FPGA.
> But that's a wholly uninformed guess; it could be either way faster or way
> slower.
It should be possible to catch up to a NVAX, but it
probably is on
really modern low cost FPGAs.
Thar Interwebs tells me that the KA650 has roughly 2.5 VUPs, with a VUP
equvalent to the bog standard 1977-vintage VAX 11/780, and further that the
11/780 ran at 5MHz and the superficial design elements seem similar to a CPU I
am more familiar with, the 68000. The VAX has paging hardware -- the giveaway
is in the acronym! -- which makes it a bit more complex, but we're still in the
same sort of ballpark.
So, here's a soft 68000: https://github.com/alfikpl/ao68000
The README.md notes that it has similar IPC to the 68000, is good for up to
about 82MHz, and uses roughly 5,000 LEs and 46kb of memory. I reckon this means
you could get four VAX cores onto the relatively low-specced Cyclone IV that
comes on the dirt cheap DE0-Nano FPGA dev kit.
The NVAX is 80-90MHz which is pleasingly similar to the maximum speed of that
68000 core. Did you fancy a cluster of four NVAXen that runs on a chip that
costs something like $15 in bulk and can be powered by a lemon with a couple of
nails banged into it?