[Coco] Coco Sound - Cartridge Input

[John W. Linville]

Wow...someone needs to catch-up on his CoCo Crew listening! :-)

I recommend Episode 5 as a starting point for some info on the
cartridge port...

	http://cococrew.org

Beyond that, keep your ears open during other episodes for mentions
of the Game Master Cartridge (GMC) and/or the SN76489.

Enjoy!

John

On Fri, Jan 04, 2019 at 01:07:12AM -0700, Andrew wrote:
> I was recently looking over the service manual for the CoCo 2, and was
> reading about the fact that there was a sound input line from the cartridge
> connector (IIRC, it bypassed the DAC).
> 
> Without researching it (I may be wrong), did only the SSC use that line? Or
> what about the Spectrum Analyzer cartridge (how did that work - unless I
> didn't read the schematic properly and that line doesn't bypass the DAC)...?
> 
> ...and did the CoCo 3 have a similar input line from the cartridge
> connector? I didn't check it's service manual to find out.
> 
> I just recently purchased and received a set of several SN76489 chips; it
> seems strange to me that Tandy/RS neglected the sound capabilities of the
> CoCo so much, and never saw fit to add something like this chip in. It would
> likely have been a cheap addition, even back then - it was certainly used on
> plenty of other machines of the era.
> 
> I also wished they had done something like dual processors or similar,
> though that would have boosted the complexity and cost of the system
> significantly for the time - so it's understandable that they didn't.
> 
> Oh - and one other thing if anyone can answer: What is the difference
> between the two PIA chips on the CoCo (2? not sure if same on the 3)?
> 
> There was one chip that is the 6821 - plain and simple. But there's a second
> chip that has a different number (don't recall what), but in the SM is
> marked as being a 6821 "select" chip? This is mentioned a couple of times in
> the SM, but it never says what it means by "select", or the reason for the
> different number. Maybe more is said in the datasheet for the 6821; I
> haven't looked.
> 
> Lastly - I know of a source here in Phoenix which has tubes upon tubes of
> 6821, and a particular variant of the 6809 (unfortunately, not the 68B09E) -
> among other vintage parts.
> 
> It's Apache Reclamation and Electronics, if anyone cares to know. I've
> purchased small numbers of these and other parts from them, but I know for
> certain they have a ton more stock of these parts (seen 'em with my eyes).
> If I had the money I'd purchase the entire stock, but they know what they
> have...
> 
> Over last weekend I grabbed some MOS parts (some RIOT chips and some TIAs -
> I think those were the parts - plus a particular 65xx CPU variant); got
> those and some 40 pin wire-wrap sockets...
> 
> --
> Andrew L. Ayers
> Glendale, Arizona
> https://github.com/andrew-ayers
> 
> -- 
> Coco mailing list
> Coco at maltedmedia.com
> https://pairlist5.pair.net/mailman/listinfo/coco

-- 
John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.