MBP Superdrive fail to read work-around!

Question

I have discovered a bizarro work-around to get the data off of your backup DVD's if your MBP Superdrive is failing to read properly.
I have a brand new 17" MBP Core 2 machine and the DVD will not read any more than the first half of the files on my backup DVD disks from my old PowerBook which i no longer available to use for xfer.
When all my backup DVD's exhibited the same problem (will copy about 2G of data and then fail with file read error) I suspected the drive rather than the media (I also saw discussions here).
I inserted a movie DVD to see if it would fail to play that as well, but the commercial movie DVD worked fine, even through the final credits. That seemed strange. I reinserted the backup DVD I had just been struggling with, and it now read the files that failed several minutes before! I now got 9/10 the way through the DVD before it again struggled and then failed to read a file.
Replacing the DVD with the movie, I again ran the credits at the end of the movie for a few moments, then ejected it and replaced it with the 'bad' DVD. I could then read the last few files off of it. I continued with this silly '"manual dexterity test" (remember this test from the days of the original 128K Macintosh with a single floppy disk drive?), and got through all 7 of my iTunes backup DVDs. I think I lost maybe 3 to 5 songs to bad DVD tracks, so that was a 99.9999% success rate, rather than a less than 50% success rate that I started out with.
The important points in the process are:
- this obviously won't work with a "multi-DVD single file" DVD like from using the Apple Backup application. It does work for me for DVD's with > 800 big files on it;
- running the movie DVD seems to "re-set" the Superdrive's heads to the correct positions;
- the heads then gradually run astray after more reads, and can't read the data DVD properly after another ~400 files (1 - 2G) or so (your milage may vary);
- when you hear the Superdrive come to a halt, that means you're toast again and it's time to swap out the data DVD for the movie DVD;
- when you go for the next try on your data DVD, don't futz around getting onies-twosies files - select and go for the entire remaining batch - you have nothing to lose;
- after a successful copy of nnn files with no error message, IMMEDIATELY grab more files and drag and drop them as quickly as possible. Don't let the Superdrive stop spinning or you are again toast, and it's time to eject and run the movie DVD again for a minute;
- it's VERY IMPORTANT that when you get the first Finder "can't read file" error to click Ok and then IMMEDIATELY eject the DVD. Don't click on the Finder window, try to scroll up the list of files, deselect files or do anything else, otherwise the poor Finder will grind away for another 10 minutes trying to complete whatever it's doing to redisplay the current list of the directory on the DVD!
- If there is a bad file, you will have to skip it on the next cycle of read attempts - I couldn't get it to read a few files that were obviously corrupt to begin with. However, you should try to re-read the file it fails on at least once - I was successful in re-reading the file it failed on > 95% of the time!
I hope this convoluted work-around works for you if you are desperately seeking backup data!
Regards,
Walter Cooke
MacBookPro   Mac OS X (10.4.8)   brand new 17" MBP w/erratic Superdrive

Answer 1

what does the "reset" input do? check its polarity vs what the rst block expects, or better yet, just connect ext_reset_in to fclk_reset0_n.
as to why you don't see anything when you write to unaligned addresses is that your program silently crashes as axi-lite slaves don't implement them and return an error which you are not catching.