🚀 go-pugleaf

Iam poting this as it may be of general interest:

In article <21755@lll-tis.arpa> bae@lll-tis.arpa (Hwa Jin Bae) writes:
>The followings are prbably very dumb questions.
>Can anyone enlighten me with the way Inboard works?  Does it require
>an IBM-AT? . . . . 

The Inboard (and most other 386 cards) work by replacing the 80286
chip with a cable to a plug in board containing an 80386.  Normally
the board also has some form of cache and maybe some 32 bit ram.
 
This design approach uses the 80386 to emulate an 80286 at the
hardware level.  The advantage of this is that almost any hardware
the 286 'knew about' is also avialable to  the 386.  This means that
DMA and Interrupt logic needs no changes.  The disadvantage is that
the 286 only has a 16 bit data bus and 80386 cycles not comming from
cache have a very large penalty from the cache miss and 2 16 bit cycles
needed (typicaly 10 to 14 'wait states').  The perfomance is improved
greatly by adding 32 bit ram on the card.  This is why the Inboard
only gets 15 on SI.

>            Is it possible to use Intel Inboard with Z-248 by just
>replacing the 286 CPU card with Inboard?  If not, would it work if
>I just add (not replace) Inboard to Z-248? 

This is the downside of the Inboard style cards - they don't work in 
most systems !  The Inboard works in IBM, Compaq, Tandy 300 and a few
others (Zenith ?????) but will not work in ATT 6300+, HP Vectra and
almost all systems that will run over 8 Mhz (Call Intel for an up to
date list of systems).  The only card I have found that will work
in the 'not quite 100%' systems is the PC-Elevator 386 from Applied
Reasoning in Cambridge ma.  This works in PC's XT's and AT's.  The
downside of the Elevator is that it will not currently run U**X or
Xenix.


-- 
John Pettitt G6KCQ, CIX jpettitt, Voice +44 1 398 9422
UUCP:  ...uunet!mcvax!ukc!pyrltd!slxsys!jpp  (jpp@slxsys.co.uk)
Disclaimer: I don't even own a cat to share my views !