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How reliable are A2 Dealer Diagnostics?

falter

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Jan 22, 2011
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I'm trying to fix up this very early A2+ I have. I've gotten it to a point now where it will boot many but not all things. It also has a weird issue with a non blinking cursor So I'm running the dealer diagnostics.. its passing all the RAM and ROMs.. is that pretty reliable as far as those two items go?
 
It also has a weird issue with a non blinking cursor

I could be mistaken about this, but I don’t think the Apple 2 can see if “blink” is working or not, it’s a video hardware attribute that makes character cells with a value set between 64 and 127 invert or not based on the state of a 555 timer circuit with a roughly 2sec interval.

Does the diagnostic program test the available attributes (normal/inverse/blinking) and that’s fine but only the cursor doesn’t blink, or is reverse and/or blink never working? You could test this in BASIC by directly poking the text screen buffer.

This stack exchange post has a list of the attribute mapping. I will note for completeness sake that if the II+ has a lowercase mod it may affect things.
 
I can tell you you need different versions to test integer or applesoft roms. using the wrong one will report a failed Rom.
 
I could be mistaken about this, but I don’t think the Apple 2 can see if “blink” is working or not, it’s a video hardware attribute that makes character cells with a value set between 64 and 127 invert or not based on the state of a 555 timer circuit with a roughly 2sec interval.

Does the diagnostic program test the available attributes (normal/inverse/blinking) and that’s fine but only the cursor doesn’t blink, or is reverse and/or blink never working? You could test this in BASIC by directly poking the text screen buffer.

This stack exchange post has a list of the attribute mapping. I will note for completeness sake that if the II+ has a lowercase mod it may affect things.
Thanks!! No I didn't expect it would test cursor blink directly. I think blinking in general isn't working. At one point in the test, I seem to recall it's supposed to put up a pattern of reverse video characters too and it just gives a solid blank white. I had this machine working previously more or less (it is missing the color trim pot).. let it sit a while and then tried it again.. and it was alive and you could blind type but you had a solid white background and inverse cursor. If you arrowed back you could see what you'd typed for a sec and then gone. It's weird stuff. I got it back to where it is now by swapping 194s in row B. But I think the real issue may be a bad socket pin or two somewhere. Anyway someone told me non blinking cursor could be rom related.. I got the ii+ dealer diag going and it said all was well with rom and ram. I just wondered if I could trust that - ie how exhaustive that test is.
 
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