[Coco] Grr!!! Bad MPI! No biscuit!

[Mike Pepe]

Gene Heskett wrote:
> On Saturday 05 May 2007, coco at yourdvd.net wrote:
>> I believe Marty Goodman once recommended that the ls245 in the CoCo AND
>> the MPI be replaced with a faster version (the ''F'' version, I think
>> he mentioned). -r
>>
> 
> The F version might work, but I think I'd troll the manuals and find one that 
> has a better controlled turnaround behaviour.  The F is a copper plated 
> bottom cast iron power hog, and since it runs from the coco's power supply 
> rather than the mpi's, we don't need to heat that puppy up anymore than we 
> have to.  Its typically 3 degrees from signing a ~30~ now.  I had in mind 
> maybe the 74HCT245, but I'd have to check the books to be sure about that.  
> Speed isn't what we need there, a few ns of tristate time between directions 
> is. IIRC 10ns of tristate time would clean that problem up like a spray of 
> Mr. Clean & a Bounty towel. :)

Gene, if that's really the problem, why don't we engineer a little 
daughter card with a couple of LS241's back-to-back. You could use some 
inverters to add some propagation delays to ease off the timing- using 
two tri-state drivers instead of one integrated one means the timing can 
be tweaked in both directions.

> OTOH, the next problem is those solder coated edge connectors.  I got tired of 
> messing with those, sawed them off, and spot soldered a gold plated strip I 
> sawed off an old pc video card.  End of that problem. :-)
> 

-Mike