Re: Help me get my childhood Apple //e running again

[Linards Ticmanis <ticmanis@gmx.de>]

On 04/30/2012 07:33 AM, Tom Moertel wrote:

> I doubt it has anything to do with serial or Linux issues. I was able to download the ADT 2.4 client to the Apple //e and use it to successfully upload disk images to ADTPro server on the Linux host using the exact same set-up.  No problems.  So the serial connection works, the Linux host works, and ADTPro server on the host works.
> 
> What doesn't work is the ADTPro client in the same environment. Maybe there's something weird about my //e that causes problems with the ADTPro client and not the ADT 2.4 client.  In any case, I now have a working solution:
> 
> ATD 2.4 on the //e
> ATDPro server on the Linux host
> and a serial connection between them


Well, DOS doesn't use the upper RAM "under" the ROM while ProDOS does.
Maybe you have an intermittent RAM problem up there. Try moving around
the RAM chips on your mainboard or exchanging them with the chips on the
80 column card, and see if the error moves to different bits and/or
disappears. If it does, problem solved, get some working RAM chips.

IIRC, ProDOS does the GCR encoding/decoding of most of the sector
in-place but uses an internal buffer for the last part. But I'm not
certain if that "last part" was the high (or low?) bits of every byte or
if it was the last bytes of the sector. Still that could explain your
problem. If the GCR decoding happens incorrectly, of course the CRC
would be calculated over the wrong bytes and would match those wrong
bytes, so the ADTPro server on the host side would never know anything
went wrong...

-- 
Linards Ticmanis