Date   : Thu, 10 Sep 1987 16:38:38 GMT
From   : ohlone!lll-winken!uunet!mnetor!lsuc!sq!ian@lll-tis.arpa (Ian F. Darwin)
Subject: Re: S100 68000 hardware

Ken Wallewein (kenw@noah.arc.CDN) writes:
>   One thing I'm curious about: I talked to a Cromemco guy once who said that
> their 68000 boards are not really compatible with IEE-696. Would you have any
> idea if that's true, and whether much is required for mods? I think he said
> they require 16-bit memory access. It seems to me IEE-696 says it's optional.
> All my boards are 8-bit only. Doesn't sound like a minor difference 
> to me :-). 

It is perfectly reasonable for a CPU card to require 16-bit memory.
There is a range of valid combinations in most IEEE (count the E's) bus
architectures, including 696 (S100), 797 (Multibus), etc. They have
specifications for it, I forget the details but it's something like
M16, A24 (meaning you do 16-bit memory accesses, and support 24-bit
addressing).

The DUAL Systems' 68000 board (which I have used since 1984 and am
still happy with despite the fact that it's not a 68020 :-) ) also
requires 16-bit memories. If you want reasonable performance that is
one end of a price/performance tradeoff; if you want compatibility back
through all the ages (or at least to 1975), that is quite another.
CompuPro, having sold a LOT of 8-bit memory boards, presumably felt
that compatibility was more important.

As far as "mods", if you mean modifying your 8-bit memory boards to
work in 16-bit mode, I hope you aren't serious. When you can buy a
megabyte of 16-bit ram for $500? How much is your time worth? At
a dollar an hour, you're probably still better off going for a new
board. See the ads in Micro/Systems Journal or Computer Shopper.