Checksum: 16354
Path: utzoo!utgpu!adam
From: adam@gpu.utcs.toronto.edu (Adam R. Iles)
Date: Fri, 15-Jul-88 13:27:14 EDT
Message-ID: <1988Jul15.132714.24898@gpu.utcs.toronto.edu>
Organization: University of Toronto Computing Services
Newsgroups: comp.sys.ibm.pc
Subject: Re: PC/XT 286-based accelerator opinions wanted
References: <14382@shemp.CS.UCLA.EDU>
Reply-To: adam@gpu.utcs.UUCP (Adam R. Iles)

In article <14382@shemp.CS.UCLA.EDU> wales@CS.UCLA.EDU (Rich Wales) writes:
>My system has an 8-MHz NEC V-20 CPU.  The clock speed is software-
>switchable to either 4.77 or 8 MHz.  The RAM chips are 150-nsec.

>The accelerator I am currently thinking of is the "Orchid Tiny Turbo
>286" -- a half-sized card unit with room to add an 80287 coprocessor.

A week ago I purchased just such a card for a similar setup (except
I'm using a 8088-2 and it's not software switchable.)  The documentation,
however, SUGGESTS that you DON'T use it with a turbo system or a 8088-2,
V-20 or several other replacement chips.  This card comes with an 80286
and an 8K cache on an 16 bit bus (to the 80286.)

>the back of the computer which lets you select either the 286 or your
>original CPU.  The Orchid also claims to be usable at either 5 (I assume
>they really mean 4.77) or 8 MHz.

This is reffering to the 80287 not the 8088 or equivilent :-( which
leaves you with only the 4.77 Mhz bus.

>Does anyone out there who is using (or has tried) the Orchid Tiny Turbo
>286 know whether it can in fact be used in an 8-MHz turbo XT?  Would I
>be able to drive it at the 8 MHz clock speed?  Even at the standard 4.77
>MHz speed, how much faster is it going to be than my current NEC V-20
>system at 8 MHz?  Would I have to replace my 150-nsec RAM chips with
>120's (or faster?) in order for an accelerator to be worth the expense?

I haven't had much time to test the board thuroughly, but it seems to
run fine at 4.77 MHz, but it won't run at 8 Mhz at all.  Since I don't
have a V-20 in my machine I can't compare it to the V-20, but it seems
to run some programs at upto 4X as fast as the 8088-2 (at 4.77 Mhz.)
One thing to remember is that the Tiny Turbo is still going through
the 4.77 Mhz 8-bit bus so disk accesses and memory fetches outside
the cache will be as slow as a regualar PC.  If you run programs that
execute a lot of tight loops and aren't I/O intensive it should do
a good job at improving their performance, though.

>-- Rich Wales // UCLA Computer Science Department // +1 (213) 825-5683
>   3531 Boelter Hall // Los Angeles, California 90024-1596 // USA
>   wales@CS.UCLA.EDU      ...!(uunet,ucbvax,rutgers)!cs.ucla.edu!wales
>   "We would all become unpeople, undoing unthings untogether."

Adam Iles -- adam@utgpu
	  -- adam@vm1.utcs.utoronto.ca

All comments above do not necessarily reflect the beliefs or opinions
of any person alive or otherwise.
-- 
    
        Any opinions stated above may, or may not, refect those
        of any sane person living, dead, or just sleeping.

       Adam R. Iles:	adam@utgpu