> Subject: Should we provide ISA bus support?
> No external bus at all:
> * Very cheap
-> Very easy to design, probably get it right the 1st time.
-> Very little board space
> * Make expansion rather difficult
-> One would have to go back to the 'sources' and do a new board
layout, and have new boards made
> R3000 specific high bandwidth bus (local bus?):
> * Peripherals that we add later can go fast.
> * Designing a high speed expander bus is problematical
> (lots of wave calculations)
> * Connectors for high speed busses are expensive.
> * No cards available, unless we make them.
-> Very difficult to design, not just the motherboard but each
new board that you want. No _cheap_ expansion.
> R3000 specific slow speed 8-bit bus:
> * Cheap, small connectors
> * Easy to provide for on the motherboard
> * Simple to make cards for
> * No cards available, unless we make them
-> Cheaper and easier than a high-speed bus, but still not
> ISA bus:
> [...] the master DMA is probably the hardest to provide
> since it requires access to the main memory.
The Adaptec 1542 is the only bus master I know of. Motherboard DMA
obviates that one.
> The 16 to 8-bit translation is a convenience for the programmer that
> allows a 16 bit access to an 8-bit card; it can be programmed around.
> Slave DMA can be easily attached to the 3730....
What do you think of some compromise that would be compatible with
some ISA-bus boards but not others? Or is that your point? I
already suggested the 8-bit PC/XT bus, maybe a limited 16-bit
> How many sockets to provide?
> This is a question of how much board space we have and what others
That's all there is to say.
Ted Spradley Recognition International, Inc. Opinions are mine, not theirs.
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