<Why do you assume that ISA -> Intel processor? It may be something
<totally different, something that doesn't have efficient block transfer
<instructions.
Like a z280?
<I see a _lot_ wrong with the ISA signal definitions. For one thing the
<IRQs are edge triggered, active high, when any sane designer would make
<them level triggered active low (had IBM done this it would have cost
<them an extra couple of TTL chips on the PC motherboard. It would also
<have allowed the sharing of interrupts). For another thing there's no
<proper bus request/grant (multiple masters are almost essential IMHO).
So the interrupts are upsidedown and stoopid, it's useful as is none the
less. The yabut is for small systems it's fine.
<As I understand it, the aim is to make a PC (meaning something that runs
<a useful open OS like linux or *BSD) and which has 'modern' features like
<a good video card. Not to make the equivalent on an S100 system
Consider possibility number 3, something that is hybrid, having the features
of s100 like system but modern IO and a different bus.
<> known, and one doesn't need a video board right off the top. The WD1003-
<> board is well uderstood and the EIDE interface emulates that pretty well
<
<Sure. Now where do you propose getting schematics for this I/O card, and
<where are you going to get a data sheet on the ASIC that almost certainly
<appears on it. This is supposed to be _open_ hardware. This implies full
<schematics, not undocumented PCBs.
Treat the card as a functional black box. Herc, CGA and VGA video is well
enough known and the addresses are not secret. It's not a requirement to
knwo the tiny design details of the 8042 keyboard controller to get it to
give keycodes. Most of the floppies are the base 765 circuits pushed into
a chip, same for serial and IDE is not a secret. Based on what I've seen
of some of those cards the less I know the better!
Allison
Received on Sat Jul 03 1999 - 23:07:51 BST