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From: doug@certes.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: 12 - 50 Mip Amiga 2000 CoProcessor?
Message-ID: <8707181004.AA14081@unisoft.UNISOFT>
Date: Sat, 18-Jul-87 01:08:26 EDT
Article-I.D.: unisoft.8707181004.AA14081
Posted: Sat Jul 18 01:08:26 1987
Date-Received: Sat, 18-Jul-87 21:03:23 EDT
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> How would you like a 50 MIP board plugged into your Amiga???

There's been some confusion as to whether this is possible, so here
are some comments to clarify the issue.

The Definicon board works in a *standard* IBM PC, so there's no particular
reason to think that it would fail in the 2000's PC bus.

And more specifically, it comes with 1 megabyte of on-board 55 nanosecond RAM,
interleaved, to act as an efficient "cache" to the slower RAM external
to the board.  So the 2000 bus won't have to handle the 12-50 Mhz data rate.
I suspect that the local memory is nothing but vanilla local memory, and
that any caching would be done by software, but that doesn't really effect
these issues.

It is absolutely correct to point out that such a board could not
achieve anything close to 12 MIPS if it were addressing memory solely
through the 2000's PC compatible bus, but as long as it is addressing
memory on its own board, it should have no problems. Cache misses will
slow it down, but 1 Meg is enough to eliminate 100% of the cache misses
in at least certain types of applications.

Chuck McManis tells me that the real reason that Definicon claims 12MIPS
vs. Sun's 10MIPS is that they used a raw figure of instructions per second,
whereas Sun took into account the fact that it may take more RISC instructions 
to accomplish the same work as CISC instructions, and did a lot of benchmarks
that resulted in a figure of 10 Vax-11/780 MIP-equivalents.

The biggest drawback to the Definicon board would be simply that it could
only benefit from software that was written specifically for it, whereas
an add-on 68020 (68030, 68040, etc) processor can run programs originally
written for the vanilla 68000. This could still be a benefit for cpu-intensive
applications, such as ray tracing.
	Doug Merritt		{ucbvax,sun}!unisoft!certes!doug