*updating* 8088's

[Allison]

>
>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.

>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
>