Hello people,
This mailing list is the result of long trans-pacific telephone calls
between Neil and myself. :-) Now that we've settled on a motherboard
as the basis for the design, and I've had a chance to listen to some
of the discussion, I'd like to outline some of my original design
thoughts...
CPU
Neil's suggestion of using the R30x1E range is great - we can
do the prototyping with the cheaper 3051 to prove the design,
and do some of the initial porting, and then those who need
the FPU can simply pop in a 3081, as they're pin compatible.
RAM
Here's where I differ from most: my belief is that 8 or at
most 16 SIMM sockets is plenty, as 16MB of memory will run
things nicely, and 32 or 64MB would be enough for most people.
IO
Neil's suggestion for the RAM/IO/DMA controller (3070??) means
that implementing most of the IO is trivial (it provides 8 and
16 bit busses for low-end IO chips).
My original thoughts included putting single-chip ethernet and
SCSI ports on the board, as these would give 32 bit IO in the
critical areas, though I worry at being able to get them in
something other than PQFP.
The ISA bus could be used for floppy/serial/parallel, as these
cards are plentiful and cheap, whereas a similar amount of 4
or 6 layer motherboard space is expensive.
VIDEO
The ISA expansion bus could readily be made VESA local bus,
thus giving access to a very broad range of video cards, where
the VLB versions give full 32 bit access and acceleration.
As for the 34010: there is no way that we can compete on
performance, price etc. for FAST video hardware with the
mass-produced VGA/SVGA cards.
I have no great objection to a SIMPLE video interface such as
the DMA-driven one Neil mentioned, though I think most people
have VGA/SVGA video cards they could (and would rather) use.
Keyboard
This is probably best done with a 8041 microcontroller (or
some other - what about a PIC?), as it reduces main CPU
overhead.
Expansion
As mentioned above, the main way of doing this is through the
ISA/VESA bus, as it gives us access to sound cards,
floppy/serial/parallel cards and a myriad others.
There's also nothing stopping you putting space for a 'native R3000
local bus' connector for those that want to design their own
I/O cards of course [or those addicted to speed :-]
Paul
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Paul Antoine, Softway Pty Ltd Net: paul@sw.oz.au
PO Box 305, Strawberry Hills, NSW 2012, Australia Tel: +61 2 698 2322
Level 2, 79 Myrtle St, Chippendale, NSW 2008, Australia Fax: +61 2 699 9174
"Proper management technique must include checking that all staff have
play-lunch and that there are no unfair swapsies."
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