Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Slow GVP '030 accelerator board
Message-ID: <15980@cbmvax.commodore.com>
Date: 20 Nov 90 16:29:52 GMT
References: <5749@crash.cts.com>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 49

In article <5749@crash.cts.com> lkoop@pnet01.cts.com (Lamonte Koop) writes:
>jma@beach.cis.ufl.edu (John 'Vlad' Adams) writes:
>>In article <1990Nov16.175346.4884@maverick.ksu.ksu.edu> yeewei@matt.ksu.ksu.edu (Yee-Wei Huang) writes:

>>>GVP 3001 accel card w/o '882 and w/o 32 bit ram

>>>	When I run performance tests on the machine, I show only a 20%
>>>increase over the stock 68000! 

>>You are lucky to see that much of a performance boost.  Don't
>>forget, the 030 fetches memory in four-byte chunks through
>>the normal Amiga bus.  Therefore, you slow down with the wait
>>states and the double fetch.  An 030 will not outperform the 68000
>>without 32bit fast ram.

>No...he is correct in that something is wrong here.  Yes, the 030 does
>longword instruction prefetches, and running on a 16-bit bus will cause a
>performance hit, but with the 030 caches active, he should be seeing
>performance around 2-2.5x that of a stock A2000.  

Absolutely wrong.  While on a few select (and meaningless) benchmark programs,
you may see that, in reality, 20% isn't an unreasonable number.  Especially
if he's got his data cache off.  Try a benchmark that's at least reasonable, 
perhaps Dhrystone 2.1.  

>The instruction cache should 'buffer' some of the hit taken by the operations
>on the 16-bit bus.  

It does.  Without the I-Cache, the 68030 on the 16 bit bus will run slower than
the 68000 on most things, absolutely guaranteed.  But it's not perfect; you 
still lose quite often by wasted 16 bit fetches -- the cache isn't all that
effective outside of inner loops; as few as 16 instructions can totally 
overwrite it.

>The 030 (and 020 for that matter) instruction caches are activated
>automatically by the OS during system startup, so I don't see where the cache
>should be off, so I would suspect a problem with the board. 

No problem with the board.  The 20% is just about right; you mileage will,
of course, vary with the benchmark selection, meaningless benchmarks need not
apply.  The A2630 will behave the same way if you turn off its Fast memory;
that's exactly why it doesn't ship without Fast memory.

>--LaMonte

-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
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	Standing on the shoulders of giants leaves me cold	-REM