If you ever look at how interrupts are implemented on STD bus, you'll
run in fear. There are only two options, chain the slot to slot
interrupt line (assuming all slots are filled downstream of the CPU) and
share the one request signal - implementing any CPU-specific interrupt
requirements like an vector placement for x86 - or you can home run IRQ
lines independently of the STD bus signals. Most cards did the later or
just put all peripherals that will ever need IRQs on the CPU card
itself.
STD bus is pretty antiquated.
-Alan
On 2017-11-20 00:54, Chuck Guzis via cctalk wrote:
On 11/19/2017 08:11 PM, Ken Seefried via cctalk wrote:
More importantly, the vast number of compatible I/O cards that were
produced. Much alternative history to be pondered.
So we agree on parallel standard buses, that STD bus is a strong
contender with varied processor base.
There *is* STD32, but it's a bit of an abomination, like EISA. It
extends the bus to 32 bits and retains compatibility with 8-bit STD.
But there's a price to be paid--special connectors (like EISA) and more
complex interfacing logic (to accommodate the older STD).
Finally, it's pretty much a sole-source standard--Ziatech came out with
it, and to the best of my knowledge, is the only firm that ever
produced
STD32 cards.
--Chuck
