[Coco] 8 slot multi pak

[Dave Philipsen]

In fact, now that I remember, I designed a MC68HC11 CPU card which 
replaced the 6502 card and it drove the backplane with a single 
74HCT245.  The 'HC11 runs at 4 MHz internal clock speed and I think I 
used the clock-stretching feature to slow down to 1 MHz on the accesses 
to the cards on the bus.  So, to correct the information below, the 6502 
cards ran from around 1977 until about 1993.  The 'HC11 cards started 
running the systems from that point until today.

The 68HC11 is a processor very similar to the 6809 in many ways and my 
experience with the 6809 made it really easy to transition over to the 
68HC11.  The only thing you can't easily do with it is write 
position-independent code as those types of instructions along with a 
user stack are missing.  I so wished and hoped for Motorola to come out 
with a MCU with a 6809 core but they never did.  They later came out 
with the 'HC12 and 'HC16 but they never became very popular and I never 
used them.

Dave


On 1/19/2017 8:21 AM, John W. Linville wrote:
> Did you work for Chuck-E-Cheese???
>
> On Wed, Jan 18, 2017 at 01:32:28AM -0600, Dave Philipsen wrote:
>> Yes, that's possible.  I have some old passive backplanes that were used for
>> an animatronics system that used a 6502 processor at 1 MHz as the main board
>> and the CPU card with just a single set of buffers would run 8 or 9 other
>> cards on the backplane.  The backplane fit into a 19" rack and I don't
>> believe there was any kind of termination on the end.  Literally hundreds of
>> these card cages were made and used about 12 hours a day, 365 days a year
>> and some are still running today (since 1977) and have had no problems in
>> that regard.  Some expansion cards had 6821s, some had 6850s, that sort of
>> thing.  The backplane PCB was double thickness - .125".
>>
>> Dave
>>
>>
>> On 1/18/2017 1:18 AM, RETRO Innovations wrote:
>>> On 1/18/2017 12:44 AM, Dave Philipsen wrote:
>>>> I think you could probably drive 8 slots with a single set of
>>>> buffers.  Just make sure the buffers have a high fanout.  I think
>>>> some buffers can do 20 or more TTL loads on fanout.  And you might
>>>> also want to experiment with termination on the end of the lines.
>>> I meant to also note that the capacitance might be an issue, but forgot
>>> to add that before sending.  TI and S-100 bus machine shave 8-12 slots,
>>> but most include buffers on each card to deal with the issue.
>>>
>>> Jim
>>>
>>>
>>
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