Jump to content
Dizzy

Atari 800 strange problem ...

Recommended Posts

Thanks a lot ! My PAL 800 board is the one from the bottom left in your pictures.

So I cannot replace a 6502C by a 6502B, but can you confirm that I cannot also replace a 6502B by a 6502C ?

Unfortunatly I do not have any XL/XE computer ...

They cannot be swapped either way. They interface to the system bus differently.

Share this post


Link to post
Share on other sites

Thanks a lot. So I have no other choice than buying a 6502C without being sure that the problem comes from it ...

Share this post


Link to post
Share on other sites

 

 

I'm not familiar with UK/Germany/EU companies.

You can look in the Atari8bit FAQ and get EU companies.

 

http://faqs.cs.uu.nl/na-dir/atari-8-bit/faq.html

Nope, That not it.

 

You want the Atari 8-bit vendors and developers list. You can find it from the A8 FAQ mentioned.

 

Nope again: at...

 

http://www.faqs.org/faqs/atari-8-bit/vendev/

 

... It has lots of EU vendors, but I did a quick look-see and didn't see much hardware vendors.

It was too many to read.

I know Best has the 800 CPU PAL card.

Edited by russg

Share this post


Link to post
Share on other sites

They cannot be swapped either way. They interface to the system bus differently.

Actually, they work almost exactly the same as each other, with the one exception of the /HALT pin. If you tie this pin to 5V, then a 6502C should work in place of a 6502B. You may not even need to, if the /HALT pin floats high (as many TTL compatible inputs do), although even if it does, you'd best tie it to +5V somehow, since this is not in any way a guaranteed behavior.

Edited by Joey Z

Share this post


Link to post
Share on other sites

I think it's a bit more complex than that. Sally also reassigns the RW pin, for whatever reason (the original just becomes NC). Possibly the halt circuitry is something off-chip and it was just a physical requirement (has anyone decapped a Sally?)

Though of course if you made up an adaptor with proper reassignments there's no reason a Sally shouldn't substitute for a 6502B.

 

 

306px-MOS6502.svg.png6502.gif

Edited by Rybags

Share this post


Link to post
Share on other sites

There is still something I cannot explain : I know the problem comes from the CPU board, but not from Antic or GTIA. So the last guilty processor may be the 6502, or a small electronic component (like a resistor).

But I do not understand why a cartridge game works fine ? If my 6502C is bad, why does it work fine when intensively used for running a cartridge, why is it crashing when just typing a text in notepad or Basic ?

 

It is a non sense to me, I really cannot explain that, does anybody has an idea of the differences in the CPU (6502) usage while running a cartridge game or while just typing a text in the notepad ?

Edited by Dizzy

Share this post


Link to post
Share on other sites

Flaky CPUs can be subtle. You can have a leaky or slow transistor in the CPU that causes certain operations to fail, but others to succeed. It can even be temperature dependent. In this case, some software will work and some won't.

 

If you have a 7474 or 74LS74 on the other board, you can try swapping it for the 74LS74A

Share this post


Link to post
Share on other sites

Yeh. man, like IDK and stuff. Now that things have been swapped out via trial and error. Maybe a more technical approach is needed with scopeses and meeders and stuff.

Share this post


Link to post
Share on other sites

Unfortunately the CPU boards I came across yesterday were all older boards with the 6502B. I could try checking again today or tomorrow though.

 

I'm sorry but what do you mean ?

I came across a stash of 400/800 CPU and memory boards yesterday at a local computer surplus shop I frequent, I posted a status update asking if anyone wanted one since I have no need for them and I'd love to see them go to the community. Edited by ApolloBoy

Share this post


Link to post
Share on other sites

Thanks a lot anyway. I will now buy a 6502C on ebay ... and I will cross my finger hopping the faulty component was it ..

Share this post


Link to post
Share on other sites

Or you could buy a whole CPU board with a 6502B on it and swap in your PAL ANTIC and GTIA.

Is there a PAL version of the old board?

Share this post


Link to post
Share on other sites

Flaky CPUs can be subtle. You can have a leaky or slow transistor in the CPU that causes certain operations to fail, but others to succeed. It can even be temperature dependent. In this case, some software will work and some won't.

 

I experienced one of these odd failures on my 5200. After the CPU warmed up, the ghosts in my Pac-man Arcade cart would start passing through the maze walls. The game didn't lockup. The games logic just started to fail. Swapped in the CPU from my 800XL and works fine now.

  • Like 1

Share this post


Link to post
Share on other sites

Or you could buy a whole CPU board with a 6502B on it and swap in your PAL ANTIC and GTIA.

 

PAL CPU Boards are very hard to find (a PAL ANTIC and GTIA would not work properly on an NTSC CPU board, already tried ...).

Share this post


Link to post
Share on other sites

 

PAL CPU Boards are very hard to find (a PAL ANTIC and GTIA would not work properly on an NTSC CPU board, already tried ...).

I already gave info where one place (Best Electronics) has UK/PAL 800 CPU boards. see earlier post in this thread.

Share this post


Link to post
Share on other sites

I already gave info where one place (Best Electronics) has UK/PAL 800 CPU boards. see earlier post in this thread.

I know, thanks again, but this website is just horrible : different colors and underligned texts everywhere, you do not know where to click ... impossible to find what I was searching for : where do you see a PAL cpu card there ? I sent an email with no response. And even if they would have answered, the cost of the cpu card plus the shipping price for France would be too high I guess.

PAL CPU cards are hard to find in Europe.

Edited by Dizzy
  • Like 1

Share this post


Link to post
Share on other sites

I know, thanks again, but this website is just horrible : different colors and underligned texts everywhere, you do not know where to click ... impossible to find what I was searching for : where do you see a PAL cpu card there ? I sent an email with no response. And even if they would have answered, the cost of the cpu card plus the shipping price for France would be too high I guess.

PAL CPU cards are hard to find in Europe.

Kyle22 gave the URL to PAL 800 CPU board. I think it is a UK board, so you'd have to e-mail them about France.

They're very specific about e-mail. You just have to have 'Atari' in the subject line or the message is deleted as spam.

It would cost you US $20 plus about US $20 ship. Put, say 'Atari 800 CPU board' in the subject line.

I know it is frustrating and expensive, but I don't know an option. Maybe try ebay.

$40 is a lot to pay. You might get an entire 800 for that on ebay.

edit: No you can't get an entire 800 for $40.

Edited by russg

Share this post


Link to post
Share on other sites

If it was me I'd just buy an XL, chances are it'll have a socketed CPU which can be harvested for testing the board.

Share this post


Link to post
Share on other sites

The web page is horrible, but the parts are good :)

http://www.best-electronics-ca.com/800.htm

 

Thanks for this direct link ! 19.95$ is a good price, I sent another email, and had a resonse saying we need to order for at least 20$ ... I still do not know what would be the shipping cost but probably around 30$. So 50$ is a lot to pay, this is the exact price I paid for my PAL ATARI 800 (with a few accessories, box, documentation, cables, etc ...) which was a good price, I know ... So I am still waiting for to receive the Sally I ordered on Ebay (17€ shipping cost included) and still hope it will work. Of course, buying a whole cpu card would be safer.

I will also pickup an Atari 800 XL I bought yesterday (but not to fix my 800 !).

Share this post


Link to post
Share on other sites

If it was me I'd just buy an XL, chances are it'll have a socketed CPU which can be harvested for testing the board.

Especially 600XLs. I don't think I've ever seen one without sockets. In fact, I can't find a Google image without sockets.

 

How about this:

 

eBay Auction -- Item Number: 2916642311041?ff3=2&pub=5574883395&toolid=10001&campid=5336500554&customid=&item=291664231104&mpt=[CACHEBUSTER]

  • Like 1

Share this post


Link to post
Share on other sites

 

Thanks for this direct link ! 19.95$ is a good price, I sent another email, and had a resonse saying we need to order for at least 20$ ... I still do not know what would be the shipping cost but probably around 30$. So 50$ is a lot to pay, this is the exact price I paid for my PAL ATARI 800 (with a few accessories, box, documentation, cables, etc ...) which was a good price, I know ... So I am still waiting for to receive the Sally I ordered on Ebay (17€ shipping cost included) and still hope it will work. Of course, buying a whole cpu card would be safer.

I will also pickup an Atari 800 XL I bought yesterday (but not to fix my 800 !).

That is not on the up and up. Refuse your order because of a nickel, when you and they know it will take more than a nickel to ship it.

Share this post


Link to post
Share on other sites

Bad news ... the 6502C replacement did not solve my problem ... And I still cannot understand this strange situation :

- If I replace the current 6502C by a 6502B (new one), then when I power up the Atari 800 I get a brown screen.

- If I replace the current 6502C by a 6502C (new one), then when I power up the Atari 800 I get a brown screen (same result !).

- If I put back the original 6502C, then the cartridges work fine, the only problem is when using basic or notepad : freezes after a few seconds of use ...

 

So if the problem does not come from the CPU (or GTIA / Antic), why only the original CPU work almost fine (but not well) ?

 

Anyway, now that I have a 800XL, can I swap the Antic / GTIA from it to insert them into the 800 ? (I don't think so as Rybags told me they are unic to each system...)

 

I guess that now I will have no other choice than buying a new PAL CPU board ... Aaargh !

Edited by Dizzy

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...