26 Jun
2020
26 Jun
'20
11:44 a.m.
On Jun 26, 2020, at 1:46 PM, Tom Gardner <t.gardner
at computer.org> wrote:
Paul
Thanks, I had found this ad a while ago but thought it was ?-inch. Upon careful reading
all the notes I found, "Errors per roll based on recording 7 tracks on rolls ?"
x 2500'. "
It looks like 3M may have called their computer tapes "Instrumentation" tape
until the late 60s
Tom
"Instrumentation tape" sounds like a reference to instrumentation recorders,
which were devices used to record N channels of analog data. Typically this was done by
FM-modulating that data for the actual recording process. I've seen references to
heads for such machines in widths from 1/4 inch to 2 inches depending on the number of
channels needed. I believe instrumentation tape was usually supplied on reels that look
like professional audio tape reels -- metal flanged reels with hubs somewhat larger than a
standard computer tape hub, with 3 small notches.
Some early computers used tape like that for data recording; for example, the
Electrologica X1 used 1/2 inch instrumentation tape reels, recording data at 400 DPI (NRZI
I think) in 10 (!) tracks. Those were vaguely like DECtape -- random access rewritable
blocks -- but with variable rather than fixed length blocks.
Recovering data from such reels is an interesting problem today.
paul