Re: Apple emulator for IBM

[jim@calico.litterbox.com (Jim)]

As Mr. Mates pointed out in private e-mail to me, my generalization about
8 bit ISA boards in 16 bit slots makes one assumption:  that the 8 bit
board will physically FIT in the 16 bit slot.  Some really old boards
used the area on the board immediately in back of the card edge connector
(where the rest of the 16 bit slot is) for stuff

I've seen this on exactly 1 card - my original IBM CGA card.

Beyond that, he asserts that not all 8 bit cards will work in a 16 bit slot.
I've seen exactly 1 8 bit card that would FIT not work - an EGA video card.
I didn't do a lot of trouble shooting to determine WHY this was - I 
suspect the bios on this 486 board just wasn't happy trying to talk to EGA - 
but there it is.

The only compatability issue I can think of beyond the shape of the board is
that the original XT ran its bus at 4.77mhz, the same as the CPU.  Modern PCs
run the ISA bus at 16mhz.  Most can cut that speed to 8mhz for compatibility
purposes.  If the board was designed explicitly for 4.77mhz XTs, this might
be a problem, but since pc clones of the day sped up the bus with the CPU,
unless the card is REALLY old, I can't imagine it will have this problem.

I forgot about these issues.  I've been in the 486/pentium/pII world too long.
Don't EVEN get me started about the incompatibilities between PCI-1 and PCI-2.
And plug and play is the tool of satan.  This is WHY I own apple2s. :)
--
Jim Strickland
jim@calico.litterbox.com
-----------------------------------------------------------------------
Vote Meadocrat!  Bill and Opus in 2000 - Who ELSE is there?
-----------------------------------------------------------------------