Re: 8250 and C64 disks

From: Nicolas Welte (
Date: 2006-04-02 18:13:37


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 


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

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