[Coco] Multipak redesign/replacement

[K. Pruitt]

----- 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
> -- 
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Genes Web page <http://geneslinuxbox.net:6309/gene>
>
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>

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.