[Coco] FPGA CoCo

[Gene Heskett]

On Monday 27 March 2006 10:09, jdaggett at gate.net wrote:
>On 27 Mar 2006 at 0:06, Gene Heskett wrote:
>> This is beginning to sound rather appetizing James.  Do keep us
>> posted, and see if you can come up with a cost for the finished
>> version.  Then another question sticks up its hand and waves for
>> attention, & that is: Are you going to do an interface that will let
>> us use our current cartridges, disk, seriel etc cards as we now use
>> them in the multipack. Or is that so far down the road its not a
>> visible object yet?
>
>******
>
>Right now things are being done in a XC2S300E FPGA(Spartan2e). IF I
> were to to go to production it will end up in a Spartan3. Most likely
> an XC3S400. That part is half the cost of the part I am using now.
>
>Like Mark stated with his project, Basically this is just beyond the
> feasability stage. The problem making hardware backward compatible is
> that the 40 pin card connector used in the Cocos are obsolete and as
> rare as hen's teeth. The only source that I can see fo rthese
> connectors is old dead Coco mobos or MPI. I imagine a modified ISA
> connector could be used.

Yes, but those are pretty well deprecated too, although there are ISA 
mobo's in almost anyones junkboxes.  OTOH, I never did think that 40 
pin choice was a wise one, nowhere near enough grounding.  With more 
pins even dma might be doable?  That would really add some serious 
speeds to disk reads/writes as currently the best block move on a 6309 
is 11 seconds per megabyte.  That figure could be inverted to 11 
megabytes a second with the cpu furnishing only the starting address 
and the buffer size to a dma controller.  Just put the cpu to sleep 
till its done.

>That is where the rub comes in. Doing an FPGA with CPU, GIME+, PIA
> chips and other circuitry in one FPGA makes it rather difficult to be
> backward compatible hardware wise. Just doing a GIME+ chip and shoe
> horn it into a current Coco 3 is somewhat doable. But whether it is
> cost effective is another item.
>
>As the weather heats  up this summer here is Central Florida,  I will
> have the afternoons to work on this project more. Right now thrying
> to accomplish all the outside work around the house that my father
> and I can while the daytime temp stays below 90F/32C.

And then its hurricane season again...  I'd imagine even your place in 
central FL gets a good summer cleaning occasionally.

>james

-- 
Cheers, Gene
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