SMT techniques (was Re: group buy for homebrew CPUs?)
THX1138 at dakotacom.net
Sat Aug 12 12:15:30 CDT 2006
Dave McGuire wrote:
> Ethan Dicks wrote:
>> I _have_ thought about that for replacement -8/L and -8/i boards -
>> design a simple board with, say, 4 to 6 16-pin SO pads and decoupling
>> caps and a dual row of jumper pads to cross-connect the edge fingers
>> to the various chip pads to be able to replicate, say, an M111 vs an
>> M117. The "problem" is that I doubt you could get real TTL (not
>> LS-TTL) parts in SO. I haven't experimented with replacing TTL with
>> LS parts in any of my -8s, so I don't know if there would be any
>> issues or not. So far, I've always had enough of the right things on
>> hand when I go to replace a chip on an M-series module. I would think
>> that the dimensions could be on the order of 2 x the size of just the
>> area of the fingers.
>> The advantage, of course, is that it would be easy to make a large
>> number of these on one PCB panel, reducing per-unit costs. Using one
>> (or maybe two at most) base designs would also help quantity issues.
>> You could sit down one day and make a stack of a dozen M111s, then
>> make two dozen M113s the next day with the same PCB; just add the
>> right SO-parts and configure the jumpers in the right order, and there
>> you are.
> A variation on this theme might be to build a very small number of
> different types of boards, but with a CPLD on each one...a small, cheap
> one like a Xilinx XC9536 (something like $3/ea qty. 1)...then have a
> JTAG connector on each board, and squirt the "personality" into the
> board that way. I've not had a chance to work closely with
> FlipChip-based machines (unfortunately) so I don't know how much
> consistency there is on things like power pins and such, so I don't know
> if this'd be practical, but I think it's an interesting idea.
I think that skirts the appeal of a *real* "miniture PDP".
E.g., why not just do the whole design in an FPGA? It would
be a pretty boring accomplishment... :-(
OTOH, having the exact same design done in "miniature
technology" would be cool!
I've a friend who had a miniature pinball machine (intended
as a "bar top" device). Roughly 10"x24" with everything
scaled down (and made in stainless!). *That* was cool!
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