[Coco] Re: [Color Computer] CoCo 2 questions.

[Phill Harvey-Smith]

Quoting Mike Pepe <lamune at doki-doki.net>:

> 
> 
> Phill Harvey-Smith wrote:
> 
> > Wouldn't mind a copy of that, do you have somewhere where you could put
> > it temporarly for until I can download ?
> 
> Sure, grab it here:
> 
> http://www.doki-doki.net/~lamune/temp/coco2b.tif

Humm I get a forbidden error, though I can get to the other two files in
http://www.doki-doki.net/~lamune/temp/

file permissions on coco2b.tif perhaps ?

> > Right, I did wonder what those white connectors where for, daughtercard
> > with 8x41256 presumably :)
> 
> Exactly correct. Not much different than the CoCo 3 512k upgrade actually.

Right, though I meant 8x4164 :) 
 
> > Nope was not that.
> > 6809 is alive and kicking, turned out to be the 4416 RAM chips, replaced 
> > them with a couple of 4464s scaved off an old MDA card, set the 64k link
> > and presto it fired up.
> 
> Aha, excellent.

Indeed, for £4.99, remembering that CoCos where a lot less common here in the UK.
 
> > What's the difference between the normal 6847 and the T1 ?
> 
> A few significant differences. One difference is that you can select 
> green or black border in text mode. Another is the ability to display 
> real lowercase in text mode as well. Architecturally it's different in 
> (from what I've been able to discern, since I have no real datasheet on 
> it) is that none of the upper address lines (A1 and up) are physically 
> connected. Also there's an internal data latch, which eliminates the 
> external 8 bit TTL latch all other CoCos have for VDG data. I think that 
> because of this, the T1 is probably incapable of functioning in a system 
> without the SAM to drive it. Again without the datasheet I can't be 100% 
> sure of that.

Ahh, so effectivley it and the SAM become a chipset that can't operate
independent of each other (well you could use the sam on it's own but not the
6847TI), also I suppose iliminating the latch means 1 less chip so drives down
production costs when you are making thousands of them.

> The real lowercase is what probably was of interest to most people. Also 
> note that despite this enhancement, Tandy never exploited it, advertised 
> it, or even mentioned it. It was just the fact that someone noticed that 
> the 0 and * characters on "these new CoCos" looked weird!

Heheheh, well I suppose if they mentioned it, people without it would also want
lower case etc, and perhaps they didn't want to offer an upgrade path :)

Though I do seem to remember that someone mentioned a mod that you could do to
allow you to use an external character rom to get lower case, shame that's not
on the web somewhere.

> > Right, that makes sense....though this A now has 64K :)
> 
> Feel free to label it 26-3127B now...

Hehehe, well I don't think either of my CoCos, or any of my Dragons for that
matter has not been modded in some way :), even if it's just to upgrade them to
the latest version of basic, and max 64K ram :)

Phill.



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