Re: CBM 610 troubleshooting

The IEEE bus handshake lines are controlled by the 6525 at U2,
only the data lines are controlled by the 6526 at U1.
So U2 may be bad.

I did some tests on a working CBM610:
It will start up with the PLA removed, but it will not be useable, since 
there will be no DRAM accessible.
It will start up with the 6526 removed. (No IEEE bus)
It will start up with the 6551 removed. (No RS-232)
It will start up with the SID removed. (No sound)
It will start up with the 6845 removed. (No video)
It will start up with the char-rom removed. (Video not readable)
It will start up to the TIM monitor with the Basic ROMs removed.
It will NOT start up with the 6525 at U28 removed.
It SHOULD start up with the 6525 at U2 removed with no IEEE bus. Since 
this one is soldered in, I did not test it.
Without the Basic ROMs and PLA, TIM will work fine in bank 15. CTRL-G 
will ring the bell. The IEEE bus will work. (.L "$",08)

Christian

Am 24.01.2013 19:12, schrieb Michał Pleban:
> Hello!
>
> Anders Carlsson wrote:
>
>> Unfortunately, replacing the 6526 with a known good chip didn't change
>> anything. Also, I tried the 6509 from the 610 into the 710, and the
>> latter boots to Basic like it should. This suggests that both CIA and
>> CPU are good in the 610, and the problem is to be found elsewhere. Too
>> bad the 6525's aren't socketed, as I acquired a few from Rob before.
> That's too bad. If you don't have an oscilloscope and the CIA chip is
> not broken, I guess there's not much you can do except shipping it to me
> (I do have an oscilloscope) :-P
>
> Regards,
> Michau.
>
>         Message was sent through the cbm-hackers mailing list


-- 
Christian Dirks
Toast_r@Idealine.info



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