I've been imaging old C64 floppies using a 1541 disk drive connected to my old Pentium III via a homebrew parallel cable and the Star Commander. Given that my disks are 30+ years old, I am amazed they read as well as they do. However, on occasion I get the odd Track/Sector error here and there... When the imaging is complete, Star Commander asks if I would like to record an "Error Info Block" with my image, to which I always answer yes.

Can I view this error information in my image files after I transfer them to my windows machine where I am running WinVice? If so, how?

3 Answers 3


The purpose of those error blocks is to emulate copy protection. It's not enough to do error recovery. You'd need to make copies in the G64 format which is made from the raw GCR stream.

The error block simply instructs the emulator to raise the error number when trying to access a sector that is tagged.

I'd expect that any sector with a non-zero entry wouldn't contain any usable information.

Detailed information about the D64 and G64 can be found here: http://unusedino.de/ec64/technical/formats/d64.html http://www.unusedino.de/ec64/technical/formats/g64.html

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    As I image my 30+ year old disks, some have read errors. I've been recording those tracks/sectors in a spreadsheet, and later I can examine the BAM and the files themselves to see if the data intersects with any error blocks. Frequently, fixing the linked list pointers in the damaged blocks and rewriting them within the image with a tool like di-sector is enough for data recovery ... especially for tokenized basic or seq text files. But recording the original error info is a pain. I should be able to simply view the error info block for the image vs keeping a spreadsheet.
    – Geo...
    Commented Jul 12, 2018 at 0:37

AFAIR the error info is just an attached block with one byte per sector of the imaged disk, tlling if that sector did produce a read error in the first place.

Within the plethora of tools to handle D64 files several can show the error block. IIRC C64-Studio as a one stop solution for C64 development was one of them. Similar the D64-Editor as a tools just about D64 files.

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    I appreciate the point in the right direction, but after fiddling around with C64-Studio, I'll be darned if I can see how to use it to view the Error Block Information.
    – Geo...
    Commented Jul 8, 2018 at 12:47
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    @Geo... IIRC, open the d64 file iand the file manager will display the error info - if some is attached.
    – Raffzahn
    Commented Jul 8, 2018 at 13:07
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    Yea, it's either hiding in plain sight, or something... Reading the technical docs for the D64 format leads me to believe the data is nothing more than an additional 683 bytes at the end of the image file, resulting in a D64 that is 175531 bytes in length. Using C64 Studio 5.7b I can open the disk image (d64) and see the contents, but I don't see any of the error block info anywhere... I also tried using DirMaster 3.11 with no luck. I'm gonna pop the d64 open in a hex editor and confirm those last 683 bytes contain non-zero data...
    – Geo...
    Commented Jul 8, 2018 at 14:04
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    Just to follow up. I looked at my disk image using a hex editor under windows and it definitely contains the error block with values indicating errors. But I have not been able to view this information in any of the above mentioned tools. - Raffzahn may be right, but until I have some success I'm leaving the question open.
    – Geo...
    Commented Jul 9, 2018 at 14:47
  • I'm in no way a C64 buff. In fact I did expect several others to come up with more suggestions here :(
    – Raffzahn
    Commented Jul 9, 2018 at 15:04

I wrote a python script which displays error information possibly included in .d64 files that I just published here:


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