[Coco] Re: [Color Computer] CoCo 2 questions.
dragon at aurigae.demon.co.uk
Fri May 13 04:41:13 EDT 2005
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:
Humm I get a forbidden error, though I can get to the other two files in
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 :)
Brought to you by the 6809, the 6803 and their cousins!
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