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From: pwappy@well.sf.ca.us (Jeff Walkup)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: A3000 CPU Wars!!
Summary: 25MHz A3000 - 50MHz 68040
Message-ID: <25432@well.sf.ca.us>
Date: 14 Jun 91 05:42:10 GMT
References: <16888@helios.TAMU.EDU> <22190@cbmvax.commodore.com> <22301@cbmvax.commodore.com>
Lines: 35



In article (22301@cbmvax.commodore.com), daveh@cbmvax.commodore.com
(Dave Haynie) writes:
 
>First of all, as mentioned about a quadrillion times in this very
>group, a coprocessor board can, if designed properly, up the
>motherboard clock rate of a 16MHz A3000 to 25MHz.  This works because
>it was designed to work that way.
 
Does this involve installing a new clock crystal on the motherboard?
Or does the motherboard use the co-pro.'s clock in this case?
 
>However, if the clock is unrelated to the motherboard clock ... the
>designer will have to solve the synchronization problems such a setup
>will inherently create.
[Stuff deleted]
>To use such a faster CPU to its fullest ability, though,the designer
>can stick a full speed cache or some faster 32 bit wide memory on the
>coprocessor board.
 
So it still sounds like an economically reasonable limit would be an
'040 running at 25MHz (for under $1000), since going any faster would
mean handling the sync problems and adding extra RAM on the board.
Altough I *was* confused about the 16MHz situation.
 
*However*, I can see someone making an '040 board at say 50MHz, and
having a small (512K) static RAM cache, that wouldn't be too expensive.
Although the lack of many MB of super-fast 32-bit RAM might hamper the
speed a bit, I can see it really racing through raytracing and other
floating-point-intensive operations.
Of course, this is all speculation at this point, since the 68040
doesn't seem to be shipping in quantity yet, and the only version
Motorola has done so far is the 25MHz one.
Waddaya think?