Some friend's and I have discussed putting together a board with a MIPS
R3000 family CPU to plug into an ISA bus machine.  The board would be
designed with low cost in mind, however, should still manage good
performance.  These are the proposed specifications:

        *  MIPS R3081 CPU (20, 25, 33 or 40 MHz)
        *  16, 20 or 24 SIMM sockets for 1MB or 4MB SIMMS allowing
           64MB, 80MB, 96MB of memory using 4MB SIMMS
           (actual number of sockets depends on space left during design)
        *  ISA bus peripheral card  (the interface should be able to
           sustain 2MB/sec throughput including software overhead).

The R3081 is a full R3000 CPU and MMU and a R3010 FPU on one chip.  When
clocked at 40Mhz, it delivers 35 MIPS.  I have measured a 33MHz R3000 at
about 10 times the speed of a 486-33.

The pro's and con's of an ISA bus card rather than a mother-board for
this project:

Pro's:
        *  Cheaper (no kbd cntlr, bus interface, DMA, sockets, etc)
        *  R&D time dramatically reduced (no need to build a ISA bus
           interface that every x86 mother-board must have)
        *  The mother-board becomes an I/O co-processor, leaving more
           time for the R3000 to do real work
        *  Cheaper to buy a x86 mother-board (less than us$100) and
           this ISA card, rather than to buy this card as a mother-board

Con's:
        *  I/O would have a higher latency, because the data must also
           be copied to/from the R3000 board
        *  Must also have a x86 mother-board.

I've made some initial guesses at price:

        *  20MHz CPU without FPU, 0 RAM installed:      us$450
        *  40MHZ CPU with FPU, 0 RAM installed:         us$650

These prices are not final; the final price will depend on exactly
what parts are used and in what quantities they can be purchased in.
The above guesses are based on producing 50 boards in each production
run (most companies produce hundreds, if not thousands).  The prices
are still wa...
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