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

20 Nov 2007

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Subject: Re: *updating* 8088's
   From: "Chuck Guzis" <cclist at sydex.com>
   Date: Tue, 20 Nov 2007 00:47:51 -0800
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

On 19 Nov 2007 at 23:03, Allison wrote:

  Actually it's teh other way around the 386
was more efficient than
 286 for the same clock speed. 
In 16-bit mode, I seem to recall that the 386SX was a travesty of a 
CPU; a 16 MHz SX ran nowhere near as fast as a comparably-clocked 
286.  Early 386 boxes were nothing to crow about in 16-bit mode--and 
a 32-bit software base pretty much didn't exist early on--and the 
386SX was limited to 16MB of external memory, just like the 286. 
Overall it was faster if the ISA bus was 16bits. problem was at that 
time the code had a lot of 8088 and 286isms in it so there was often 
no advantage other tha internally the 386 was bit faster. In practice
and I have a SIIG 3000 box (386sx) with 5mb to test on the 386
was faster but going from 12 to 16 mhz is not a large increment.

...
 Doubtless the 386SX board designs were low-budged also,
which 
probably figured into things.  Some 286 vendors made a big thing of 
the fact that a 286 could execute 16-bit real mode code substantially 
faster than the 386SX.  For example: 
Indeed. to save money in that still expensive ram there were a lot
of wait states inserted to accomodate 85ns simms.  That tended to 
sharply nullify any internal advantage.

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 http://www.intersil.com/data/an/an121.pdf

On the other hand, the 386SX could execute 32-bit code.  That is, if 
you had any to run in 1989. 
; there in lies the point.  CPUs as we well know generally run ahead
as Moore predicts with software lagging behind.

However, in 1989 the 386 as a huge leap ahead and sometimes over 
the 286 that not every one had.  I did that.   I went from 
8088/4.77mhz XT to INboard386/16 and from there to 486DX/33.

However... I didn't "buy in" to the PC world until after the WWW
as CP/M z80, PDP-11 and VAX wer faster, easier or on hand where 
the PC offered limited or no advantage.

Allison

...
 Cheers,
Chuck