[Coco] An 8-Slot Multi-Pak Design for my Color Computer Friends

[Little John (GIMEchip.com)]

Part 2 is here: 
http://www.coco3.com/community/2010/07/this-is-part-2-of-3-of-an-8-slot-mpi-multi-pak-interface-design-for-my-friends-at-coco3-com-andor-the-maltedmedia-list-members-from-your-friend-johngimechip-com

I'll go over it again and try to fix problems pointed out. I have no degree 
(yet anyway - would like to go to school for this stuff). Basically I've got 
three years of playing with the vintage computers that dad gave me and the 
knowledge that dad has passed on to me over the years, plus tons of reading. 
Anyway, this thing may not work - but - there is enough information here so 
that someone could make a better design. The MPI circuitry is actually an 
amazingly simple design - I think the wheel might be one of the few designs 
that are simpler than the MPI (that is a joke). The whole thing could be 
stuck into the smallest of CPLD's. I may eventually do that. Anyway - point 
out the problems and I'll try to fix them. It keeps me going. -John
----- Original Message ----- 
From: "Gene Heskett" <gene.heskett at gmail.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Sunday, July 04, 2010 6:16 PM
Subject: Re: [Coco] An 8-Slot Multi-Pak Design for my Color Computer Friends


> On Sunday 04 July 2010, jdaggett at gate.net wrote:
>>First
>>
>>A huge mistake in not buffering the data bus on the main board. If you are
>> running a stock Coco3, you do run the risk of damaging the MC6809E and
>> the HD6309E if the board becomes detached while powered up.
>>
>>Second
>>
>>why the dip switches on the Control and clock lines. A wrong setting on
>> the dip switches and you have a nonfunctioning board that can lead to
>> frustration.
>>
>>Third
>>
>>What is the function of Q1?
>>
>>Fourth
>>
>>Your ground plane on the top and bottom are basically floating planes that
>> are tied at but just a few spots. You have all your locic tied to GND1
>> and then this large plane on both sides is GND. You also have fingers
>> that are floating that is bad for noise immunity. Either use one ground
>> or tie them in a star pattern and eliminate the floating fingers.
>>
> TBT, the shacks own design re the ground plane sucks, big time.  I had to
> add more bypassing and lots of 12 gage solid jumpers to get the ground
> bounce down to the no error levels in my mpi.  I started with about 2 
> volts
> in the middle of it, referencing the clip ears on the coco's motherboard.
>
>>just a few things I see wrong or bothersome.
>>
>>By the way I have a degree in Electrical Engineering and have 23 yrs
>> experience in PC layout and design of portable electronics. SO these
>> questions do come from someone that has experience and questions about
>> the design.
>>
>>james
>>
>>On 3 Jul 2010 at 18:12, Little John (GIMEchip.com) wrote:
>>> This is my latest project, designed just for you guys and the readers of
>>> CoCo3.com. I worked on this for about 9 hours when my internet was off.
>>> Hopefully it will be of some use to some of you.
>>>
>>> It is taking a lot longer to do the write up than it did to complete the
>>> design, but I have posted Part 1 (of 2) here:
>>> http://www.coco3.com/community/2010/07/this-is-part-1-of-2-of-an-8-slot-
>>>mpi-multi-pak-interface-design-for-my-friends-at-coco3-com-andor-the-malt
>>>edmedia-list-members-from-your-friend-johngimechip-com
>>>
>>> Let me know if you spot any potential problems. I'll get part two typed
>>> up and posted by tomorrow.
>>>
>>> Enjoy. Let me know if you find any errors in my design. I'll fix any
>>> that crop up.
>>>
>>> Your Friend - Lil' John
>>>
>>> --
>>> Coco mailing list
>>> Coco at maltedmedia.com
>>> http://five.pairlist.net/mailman/listinfo/coco
>>
>>--
>>Coco mailing list
>>Coco at maltedmedia.com
>>http://five.pairlist.net/mailman/listinfo/coco
>>
>
>
> -- 
> Cheers, Gene
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> "My sense of purpose is gone! I have no idea who I AM!"
>    "Oh, my God... You've.. You've turned him into a DEMOCRAT!"
> -- Doonesbury
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco


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