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MIPS R3000 - 2nd update

To: riscy@pyramid.com
Subject: MIPS R3000 - 2nd update
From: jeremy@sour.sw.oz.au (Jeremy Fitzhardinge)
Date: Wed, 23 Jun 1993 19:17:43 +1000
Neil Russell says on comp.os.linux:
> *  I have decided that the IDT 79R3051E (the non FPU version) should be
>    used.  Since getting good pricing is hard unless quantities are high
>    I wish to stick to one type of CPU.  The board will be able to
>    accommodate the IDT 79R3081E (with the FPU and more cache) if the
>    user wishes to replace the CPU.  This would mean that full floating
>    point support routines need to be written; ho-hum.

I suspect the existing FPU emulator can form the core of a IEEE
FPU emulator.  The hard part would be replacing the 387 front end
with a mips one, assuming that the mips compiler uses a similar
subset of IEEE FPU as the 386 one.  Since they are both gcc, this
is probably the case.  Another guess: Mips FPU instructions are
not going to be as hard to interpret as 387 ones.

> *  The R3000 is able to be a little endian or a big endian machine.
>    Most operating systems that I've seen use the big endian mode, but
>    since linux runs on the 386, little endian may be more appropriate.

I don't know if it will make that much difference, but I suppose
little-endian is easiest.  Big endian will probably make talking to
ISA IO boards quite tricky.

What's your current thoughts on on-board IO?



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