Herb, I just thought of another example of my successful construction of a full, "large" (by early 80s standards) file from a QIC-11 format tape: http://microtechm1.blogspot.com/2015/11/microtech-m134-iris-r7-tape-read.htm... The file I produce on this page was reconstructed by my programs, from about 21,000 individual 512-byte blocks of data written to the tape. Each block of data was decoded from the GCR 4/5 data pulses that I captured with the logic analyzer, and then decoded straight to hexadecimal characters, which I stitched together in a hex editor. I think if we were to continue this conversation much further, it may greatly help me organize what I've done into a format that would be ready to share more quickly, so I appreciate this discussion very much! Before talking with you about this, I've mostly been working in a vacuum on this project. Just discussing this with you is helping my organization of it. On Fri, Nov 20, 2015 at 11:22 AM, Herb Johnson via vcf-midatlantic < vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
Microtech Dart wrote:
Actually, I've already done something that works well for a lot of what you mention. [With] my Universal QIC tape reader.... I've read a number of different head/track configurations with this, by finding the tracks of the 9 that overlap with the 4, and choosing the correct direction on my manual switch control.
http://microtechm1.blogspot.com/2015/09/ kennedy-6450-tape-drive-data-format.html
I have a question, but first some set-up for it. I have a point in spelling this out.
Over the years, a number of people have read off binary data streams from either cartridge tape drives or very old hard drives; they store the binary samples as huge files (relative to the original data). And there are devices like the Catweasel series of cards, which operate floppy disk drives and sample their binary data streams. "Sampling" means there's many bits saved, to detect each "bit" of real data on the medium.
Sometimes, these methods aren't sampling, they include the drive's "decoder" to produce actual binary data from the media. So a recovered "bit" is a real "data bit".
But not all of those who produce these methods, take the next step of decoding the samples into blocks of original-as-recorded data; and then decode the blocks back into the original files which were written-to the storage devices in the first place.
result: there's data "recovery" but not file recovery. I've explained what I mean by that.
Now, I've looked at the microtechm1 blog. Since like most blogs it's written as a sequence of events, there's no obvious-to-me summary of current progress, beyond the "most recent" entry. I don't have time to read all prior entries. I can see there's progress on decoding the recovered data; and some hints that data at the "block" level may have been recovered. Some posts about "here's a binary extraction". This is good work, this is hard work. But I'm not clear about how far it has gone; and I made a good-faith effort to look.
So here's my questions. Have you 1) reproduced the actual block-by-block data from the tapes you've processed ? 2) do you have programs to decode the blocks to interpret checksums, block numbers and so on? and 3) can you therefore process the successful blocks further to recover actual, individual files?
I'm not trying to minimize all the good, and necessary, technical work done. I'm asking if files have been extracted, and if so where they may be, and where the supporting programs may be. Why am I interested? I "get" your point, these methods may be useful to me, in recovering other data from other tapes or devices; as was suggested.
Herb Johnson -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net
-- Thanks, -AJ http://MicrotechM1.blogspot.com