[Coco] Sdc copy, and multi pak upgrade question

[Scott O'Brien]

I have finally joined the esteemed club of CoCo3 owners (they don't seem
too common here in Australia, judging by what is visible on ebay).

I got it with an 26-3124 MPI (also a first for me).

My question is, if I open it up, how do I tell if it has had the necessary
CoCo3 modification made, Tandy-sourced or otherwise?

Is there any documentation on the Tandy modification?


Cheers

Scott


Date: Mon, 01 Dec 2014 21:57:30 -0700
From: abqpenmaster <abqpenmaster at gmail.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Subject: Re: [Coco] Sdc copy, and multi pak upgrade question
Message-ID: <gj2fji9q76xv3mmocj5riowj.1417496250640 at email.android.com>
Content-Type: text/plain; charset=utf-8

Thanks Gene, I'll get that done.
Sean


Albuquerque,  NM USA

<div>-------- Original message --------</div><div>From: Gene Heskett <
gheskett at wdtv.com> </div><div>Date:12/01/2014  8:28 PM  (GMT-07:00)
</div><div>To: coco at maltedmedia.com </div><div>Subject: Re: [Coco] Sdc
copy, and multi pak upgrade question </div><div>
</div>On Monday 01 December 2014 11:09:46 seanruss08 . did opine
And Gene did reply:
> I got a shiny new sdc, thanks Darren & Ed.  Question though:
>
> I have been able to use the drivewire to copy programs from pc to coco
> floppy with the sdc card in my multi-pak,   but is there a command to
> copy from PC to the sd card through drivewire?  Like copy this to
> that,  or similar command? I have not been able to this far.   Or does
> everyone just use the PC to setup the files on the card?  Also,  ok to
> setup files/directories on pc?
>
> I ask because right now the only card reader is on my printer and it is
> adamant that I am not allowed to write to an sd card. I have a better
> card reader on order.
>
> Also,  right now I am using a stock multi-pak (26-3124) that has not
> been upgraded.  I bought it off ebay. I took the cover off and it's
> not upgraded.  It seems to work great though with my Coco3 haven't
> seen any problems,   should I have it upgraded anyways?
> Thanks,  Sean R.

Absolutely.  It shares its slot switching via a poorly decoded chip select
ghost that means a white to $FF7F to change the slot, will crash nitros9
by mapping out the normal $3F used for the top 8k of ram as it will write
to $FF9F which is in the multipak.  Conversely, a write to the gime chip
will muck with the slot or irq transmission ability's of the multipak.

Mark at cloud9tech.com has kits for both or all 3 versions of the
multipak.  Or he can install them for a nominal fee if you send him the
multipak.

But part of that danger will go away forever if you tie all the slot
sockets together at each sockets pin 8, which will bypass the slot logic
and allow an IRQ from any slot to reach the 6x09 in a fraction of a
microsecond.  That means no more missed interrupts from the serial port,
losing characters when online thru it.  But, that will load down the per
pin IRQ pullups by making what ever is pulling that line down to assert
the interrupt work 4x harder because when the bridging wire is in place,
it has to pull down all 4 of those resistors. Put a meter on one of the
pin 8's and check the resistors along the front edge of the board, and cut
the first 3 that you find have only an ohm or 3 from pin 8, loose on one
end.  The 4th one you find and leave alone is plenty of pullup to maintain
the logic 1 when no interrupts have been asserted.

This is actually 2 independent problems, but you might as well do them
both while the covers are off.  I fixed mine about 28 years ago.

Cheers, Gene Heskett
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