Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!aplcen!haven!grebyn!allen
From: allen@grebyn.com (Allen Farrington)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: 50 MHz MC68040 capabilities?
Summary: Be Very Careful When Discussing System Designs
Keywords: CPU DRAM 386
Message-ID: <19411@grebyn.com>
Date: 20 Feb 90 23:55:06 GMT
References: <1129@mindlink.UUCP> <9691@cbmvax.commodore.com> <1013@metaphor.Metaphor.COM>
Reply-To: allen@grebyn.UUCP (Allen Farrington)
Organization: ERGOSoft Products, Chantilly, VA, USA
Lines: 35

In Article 238 of comp.sys.amiga.hardware:

>Where are the boards with Cache?
>We're paying big bucks for speedup boards now that could buy us
>386's with more efficient design. Anybody care to comment?

>-Dallas "Down with Wait States" Hodgson

Let's be real careful when talking about cache.  Cache is expensive,
very expensive--$600+ for 64KB.

The bottom line is that any SYSTEM which does not use a cache will be
limited to about 14MHz (70nS DRAM) memory execution.  Beware of
super-fast boards which execute at 25-28-33MHz and have no cache.  Over
the past several years, CPU technology has far outstripped other
sub-system technology.  All this adds up to a CPU spending a lot of
wait-states in instruction fetches.  An example is Intel's 386/133
Multibus II single board computer.  It has a 386 running at 33MHz.
It also has a cache (I forget how large).  The point is, this board
contains 16MB of DRAM with an 8/16 wait-state penalty for missing the
cache/cache and page, respectively.

I don't agree that any 386's have an inherently more efficient design
over the standard Amiga with an accelerator board.  I do agree that
a 386 with 64KB of cache is more efficient than the stock Amiga.
Perhaps we need a large cache card for the 2630 or other accelerators.

--Allen


-- 
|------------------------------------------|
| Allen H. Farrington (703) 222-9612       | "It's like nothing we've ever
| allen@grebyn.com                         |  dealt with before."
|------------------------------------------|                    -Mr. Spock