*updating* 8088's - test-drb@ccmp.vtda.org

19 Nov 2007

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Subject: Re: *updating* 8088's
   From: Fred Cisin <cisin at xenosoft.com>
   Date: Mon, 19 Nov 2007 18:31:39 -0800 (PST)
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

On Tue, 20 Nov 2007, Alexis wrote:
  I'd like to see an 80286 to 80486 upgrade
card. It would need to somehow
 multiplex the 32-bit bus onto the 16-bit bus, perhaps running the
 multiplexing process at double the CPU clock speed. The SX wasn't 16-bit was
 it? Or am I thinking of the 386SX. If it's 16-bit it wouldn't need
 multiplexing. 
Depending on how you DEFINE "16 bit", the 80386SX is a 16 bit version of
the 32 bit 80386[DX].  It therefore is "relatively" easy to retrofit it to
replace a 80286. 
The 386SX was 32bit core with 16bit databus (modified BIU).  While
it was cheaper to build systems around and smaller too the performance 
cost was high compared to the DX.

...
 The 80486SX and 80486DX are the same bit sizes.  Their
differences involve
whether or not the math FPU is included.

I ran an 80386 board in a 5150 (8088) machine.  There didn't seem to be
much point to it.

I ran a Leading Edge model D (PC XT clone) with an Intel Inboard-386.
It gave me 2MB ram and a 16mhz CPU (beats 4.77!) and a bottleneck of
the 8bit ISA.  However it ran winders3.1 and was a whole lot faster 
than the 4.77mhz V20.  At the time it was far cheaper than a real 386
and much better than the 8088.

Allison