Isa
Isa
Fallo said...slow down to 8-bit speed
How would that work, then ? There was no support for autoconfiguration on ISA.
ISA also ran at the system clock speed. This was changed in later boards where, as was pointed out, you could select the ISA bus speed, but there's nothing in the spec that allows the speed to be negotiated by the card talking to the board.
On 16-bit ISA, the card could request 8 or 16 bit transfers from the DMA, but this was on a
card-by-card basis & transfer-by-transfer basis, not system wide.
Some DMA channels were defined a s 8-bit, others 16-bit, which caused problems.
Slapping a 8-bit card onto a 16-bit bus could cause problems, but any slowdown isn't due the bus magically deciding to run at a slower speed, or to suddenly force all other card into 8 bits if a 8 bit card is present.
Of course, I might be remembering something incorrectly, or phrasing something badly, so if Fallo has any references for the
I wouldn't mind reading up on it.
patscc