Re: 8250 and C64 disks

From: Claus Just Rasmussen (
Date: 2006-04-02 21:54:42

Hi Nicolas,

Just retried with only 1 retry - it's a lot faster, and each sector ends 
up with a "3" - don't know what it stands for, guess read-error?
The result was a 533.248 bytes large file, empty according to Vice. 
Well... this might be an empty disk, but it shouldn't be...

I then retried set to 255 retries, it's still writing "3" and it's a lot 
slower. Might indicate that my guess (read-error) is correct?!
It's really taking a long time now, so I decided to stop it, because I 
saw your new program :-D
If I recall it correct, I get an "ibcmd err" if I wait long enough.


Nicolas Welte wrote:
> Hi,
> I just had another idea. What error did you get exactly? What does the 
> program say when it exits? It's possible that the 8250 takes a very 
> long time to retry on a read error, and in this case, the GPIB driver 
> will assume a timeout and the program will exit. I set the timeout 
> value to 10 seconds which should be enough, but I can prepare a 
> program version for testing with infinite timeout, or later with 
> configurable timeout.
> For a first test, you can reduce the number of retries to 1 or so. 
> That could also help, because the retries are done in the drive, not 
> by the PC, IIRC.
> Nicolas
> Claus Just Rasmussen wrote:
>> Hi Nicolas,
>> I have a problem reading one of the 8250 disks - one of the sectors 
>> has a readerror.
>> Question: Would it be enough to remove the "exit(1);" line in the 
>> codesnip below to ignore the error?!
>>       chkin(unit,3);
>>    if (ibrd (bd,buf,256L) & ERR) {
>>              gpiberr("ibrd Error");
>>              exit(1);
>>              }
>>    clrchn();
>> Best regards
>> Claus
>> Claus Just Rasmussen wrote:
>>> [ Note: This mail was converted from HTML to text by majordomo.
>>>         Formatting might be poor. ]
>>>  Hi Nicolas,
>>>   It would be really nice if you'd help and modify the code. I haven't
>>>   got any problem to look into it myself - except that I need to
>>>   install a compiler, and I wouldn't know what to change in the
>>>   6502-code to make it work on 4040.
>>>   Best regards,
>>>   Claus
>>>   Nicolas Welte wrote:
>>>       --- Ursprüngliche Nachricht ---
>>>       Von: Claus Just Rasmussen       <>      
>>> An:      Betreff: Re: 8250 and C64 disks
>>>       Datum: Tue, 28 Mar 2006 21:35:13 +0200
>>>             A combination - some 4040 disks and also imgrd, I'm 
>>> afraid. The 4040       disks explains itself, the imgrd problem 
>>> was/is that if I specify a       filename in actual path, then it'll 
>>> be overwritten by something <2KB.
>>>                  Strange. I never had this problem here. But that's 
>>> for using a program on
>>>     only a single machine. You never know what happens on the next 
>>> one! But I'll
>>>     have another look into the source if there is something obvious.
>>>                       I managed to get my hands on a 4040 so now 
>>> I've got the HW in place to       read the disks. Really nice.
>>>             Next question: Do a 4040-version of imgrd exist? If not 
>>> - will I need to       change more than the #sectors,tracks? 
>>> (bitclock?)
>>>                  Of course the map of sectors per track and number 
>>> of total tracks has to be
>>>     fixed. Then some minor changes for the filename extension (d64), 
>>> and the
>>>     autodetection of doublesided disks has to be skipped. I use some 
>>> 6502 code
>>>     that gets downloaded into the drive, I have to check if this is 
>>> usable on
>>>     the 4040.
>>>         If you don't feel like hacking into the source code, I can 
>>> have a look and
>>>     add an option -40 to support the 4040 drive and disk layout. 
>>> (I'm sure a
>>>     2031 drive can't be supported so easily, because my 6502 drive 
>>> code had to
>>>     be changed to the completely different memory layout of the drive).
>>>         Nicolas
>>>                    Message was sent through the cbm-hackers mailing 
>>> list
>>>   --   ------------------------------------------------------------
>>>   Claus Just Rasmussen, BSc.EE.  
>>> ------------------------------------------------------------
>>>        Message was sent through the cbm-hackers mailing list
>       Message was sent through the cbm-hackers mailing list

Claus Just Rasmussen, BSc.EE.

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