Where's the cpu on my 800XL?

[matsondawson]

I'm expecting to see a 6502, 65C02, anything like that, but not one chip is labelled as such.
It's broken so I want to chuck a logic analyser on it.

[tezza]

Matt,

It's a special type of 6502 labelled CO14806. See

http://www.atarimania.com/faq-atari-400 ... ps_13.html

I was also mystified when I first started to work on Ataris. In fact I'm working on one right now. See..

http://www.vintage-computer.com/vcforum ... -Atari-400 and
http://www.atariage.com/forums/topic/16 ... n-startup/

I've ordered a new ANTIC chip for mine, which I'm hoping will solve the problem.

[matsondawson]

Tezza,

Do you have a circuit diagram for the 800XL? I've checked the 6502 and it seems to have it's reset line held low, so I need to find out what drives the reset line.
Actually, at start up it oscillates at 1.75Mhz, then settles at low.
Also I noticed the clocks aren't square but very lopsided, do you notice this on yours?

[tezza]

Reset line low doesn't sound right.

Anyway, this might help

http://www.classic-computers.org.nz/tem ... rfacts.pdf

Let me know when you've downloaded and I'll take it down. It's quite large (15MB).

[matsondawson]

Thanks I've got it, and put it up here for others that may need it... http://mdawson.net/files/800XL-sams-computerfacts.pdf

[matsondawson]

BTW that's an awesome manual, thanks!