[vcf-midatlantic] Zilog System 8000

[Herb Johnson]

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