Accelerators, array processor ?

[Howard C. Hart]

In article <5021 at brazos.Rice.edu> sungeo!geodel at prg.oxford.ac.uk (Delman Lee) writes:
>I am interested in add-on boards (accelerator, array processor, etc..) for
>Sun workstations. I have heard of 2 boards for VMEbus --- SKYbolt from SKY
>(80MFLOPS), and SuperCard from CSPI (80MFLOPS/card). 

Can't vouch for the Skybolt but we did buy the previous version, the SKY
Warrior. For our applications, it worked about as fast as a Sun 3/260 with
an FPA. Definitely a buyer beware situation.

>- Are there any add-on boards for SBus?

No for SKY and no for Mercury. Don't know about Supercard. Something about
insufficient power.

>- Any other boards of same category?

Mercury datasystems or something like that. Unlike SKY, they're offering a
multiprocessor option. Judging by the MFLOPS above, CSPI is probably doing
the same thing as SKY and banking on the i860 40 MHZ chip running parallel
instructions (get it? - 40 * 2 instructions = 80 MFLOPs...maybe).

One big word of warning before you buy. Benchmark using your own primary
applications. The thing that killed the old SKY board was VME bandwidth.
If you couldn't ship the instructions across the bus faster than it takes
to calculate the answers, you'll never see the performance as advertised.
The old SKY was benchmarked against FFTs which sit on the SKY processor
board and crunch away until the final answer comes out.  Thus, no I/O
bottelneck. If your applications are inherently sequential, you might be
able to transfer up to 2000 adds, multiplies or divides at a time, but it
takes too long to ship the answers back for the next iteration. Supposedly
these new boards are complete CPUs and floating point processors on one or
more boards, so VMEBus I/O is minimized.  I'd check it anyway.

Howard C. Hart                 UUCP:{sun!sunncal,pyramid}!leadsv!laic!nova!hart