[Coco] Multipak redesign/replacement

Sun Feb 22 11:24:27 EST 2015

On Sunday, February 22, 2015 10:54:30 AM K. Pruitt wrote:
> ----- Original Message -----
> From: "Gene Heskett" <gheskett at wdtv.com>
> To: <coco at maltedmedia.com>
> Sent: Saturday, February 21, 2015 10:26 PM
> Subject: Re: [Coco] Multipak redesign/replacement
> 
> > On Saturday, February 21, 2015 10:17:13 PM Gene Heskett wrote:
> >> On Saturday, February 21, 2015 09:16:47 PM Andrew wrote:
> >> > While I can't help with the design or such, I would be willing to
> >> > help test any resulting system, if needed.
> >> > 
> >> > That said, what I would like to see for a new MPI would be
> >> > something more akin to the few "backplane" systems that were
> >> > available back in the day in the pages of the Rainbow and
> >> > elsewhere (alas, I was a kid, and such a backplane was out of the
> >> > question to my parents). I would, though, change things up
> >> > slightly.
> >> > 
> >> > Instead of orienting the paks vertically, as in a standard MPI, I
> >> > would rather that they were oriented on their sides; think of the
> >> > current MPI, with the paks vertical, then rotate the packs 90
> >> > degrees clockwise, edge connector toward the cartridge slot.
> >> > 
> >> > There would have to be some kind of vertical interface plane for
> >> > the slot connectors; probably all the needed electronics could be
> >> > fit on a 2-sided board (heck, maybe on one side using SMT
> >> > components). There would have to be some kind of extra mechanical
> >> > support or such for the vertical board, but I think it would be
> >> > doable. An alternative arrangement might be to have the same
> >> > orientation, but the edge connectors facing toward the rear of
> >> > the CoCo (label sides of the paks to the front).
> >> > 
> >> > The nice thing about such an arrangement would be that you
> >> > wouldn't have tall packs sticking up so far (like the original
> >> > RS-232 pak - or the older floppy drive controllers); in fact,
> >> > since all paks are the same width, that's the maximum height they
> >> > would be above the level of the CoCo. If a cable connection is
> >> > doable with such an arrangement, all the better.
> >> > 
> >> > Finally - a potential thing to do might be to put a micro
> >> > controller (or something) on each end to buffer the I/O lines and
> >> > translate the signals to high-speed serial (maybe USB?) - so that
> >> > a thinner (and longer) cable between the CoCo and new MPI could
> >> > be used (though I realize that such a solution likely has major
> >> > pitfalls of its own).
> >> 
> >> Something along those lines has been on my mind since forever I
> >> think, but with a 80 in SCSI-III sort of an interconnect, between
> >> the board design we have now in the part 1 of 2 file from little
> >> John.  That, IIRC uses the same cabling as the 80 wire IDE, but
> >> would give us 40 signal wires and a rock solid ground.
> >> 
> >> I think that is just a 2 layer board that we have the eagle files
> >> for, but I am not sure how he intended to do the interconnection
> >> between the slot carrier board and the logic board we already have,
> >> which has an 8 slot capability.  I should load that up into eagle
> >> and run it thru pcb2gcode to get an idea of the logic board size
> >> when laying in the mill table as my y motion is all used up at
> >> about 5".  It may be small enough I could make the first copy on my
> >> mill.  But that will wait till the local deep freeze is over.  Way
> >> too cold now even with the keep it dry heat thats on out there.
> >> 
> >> Its been so long since I designed the encoder board for my lathes
> >> spindle that I may as well go get the latest free version of eagle
> >> and install it. And probably have to learn how to do it all over
> >> again.
> >> 
> >> I'll report, when I have something to report.
> >> 
> >> Cheers, Gene Heskett
> > 
> > A PS as it were. I did find part 2 which is a web page describing it,
> > with no links to get the slot socket carrier.  AND a note from
> > little John about a couple errors plus the fact that it didn't
> > really need 16 positions of dip switches.
> > 
> > So the Part 1 eagle files and .brd drawings were obsolete before
> > being committed to copper. Part 3 was supposed to be the cpld
> > recipe's.  Neither happened.  Since these drawings carry a copyright
> > date of 2010, its apparent that they will not be corrected.  And I
> > am not good enough to even get eagle to talk to pcb2gcode. 
> > Fortunately there is the even newer pcb-gcode that I have used
> > before, and will again if I can get the paths set.
> > 
> > The slot carrier interface is a 40 pin dual row header, but to
> > complete that we would have to consult the schematic and put some
> > sort of a naming convention on the pins so we could carry the net to
> > the 2nd board a lot easier.
> > 
> > What we have has 67 errors found by DRC (design rules checker), all
> > of which can be safely processed and ok'd. 40 of them are at the
> > ends of the finger traces where it _thinks_ the spacings are too
> > narrow but in fact are fine.
> > 
> > And I'm still moving files around so that pcb-gcode can find them.
> > 
> > This board is complex enough that I expect each side will be close to
> > a full days work for the mill as it removes copper, using the
> > etching bits I have, in cuts about .002" wide, so a 16 mill spacing
> > means it has to make 8 passes to clear all the copper away between 2
> > traces.  Its also big enough that any un-flatness of the board will
> > need to be either held flat by applying a serious vacuum, or the
> > board will need to be mapped so that the machine can follow the
> > warpage. Each piece individually of course. I'm in favor of the
> > vacuum but I'd have to rig up a vacuum storage tank since the pump I
> > have would probably overheat if it runs for 8 hours straight.  If
> > edge of board holder palette leakage can be held low enough, the
> > pump could run and pull a good vacuum in 5 minutes, then take a 30
> > minute rest before it had to pull it down to 29.5" hg again. 
> > Running full time it will also slowly vaporize its lubricating oil,
> > filling the air in the shop with a glasses fogging mist of its fancy
> > oil.
> > 
> > This, serial number one unit is strictly for debugging as the board
> > houses can do it at 10% of my cost, or less.  I don't think much of
> > the atx power supply, but elderly XT's would work as well & probably
> > 10x more dependable because a new atx supply today will last only
> > long enough for the warranty to expire. The name brand stuff like
> > Antec, is very carefully designed to last 2 weeks past the warranty.
> > 
> > However, I won't pursue it any farther unless I see the potential
> > market is at least 50 units. If someone else can work up a B.o.M. so
> > we can get an idea of chip, sockets, resistors, caps & 40 pin
> > connectors and ribbon cable, then I figure out a suitable container
> > of lexan, we might have a SWAG about the cost of a kit or assembled
> > & boxed ready to use version.
> > 
> > Realistically, is there a market for 50 of these if the kit was $60
> > and the boxed one was $120?  IDK.  You tell me IOW.
> > 
> > Cheers, Gene Heskett
> 
> I want one -  assembled and ready to go.  And honestly, at $120 I think
> it would be a bargain considering the shrinking availability of MPIs.

That makes one. :)

Cheers, Gene Heskett
-- 
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