8 Mar
2023
8 Mar
'23
1:35 a.m.
On 2023-03-07 20:23, Chuck Guzis via cctalk wrote:
On 3/7/23 17:04, Zane Healy via cctalk wrote:
I was a CE on a site with multiple Uniservo VI C units at Bell Canada in
1971-1975. They were 200, 556, and 800 bpi NRZI, and were instilled at
that site in 1968. We used a chemical called 'Visimag' to coat the tape
and see the physical bits and check that they were in line! You cannot
do that with later GCR densities!
cheers,
Nigel
--
Nigel Johnson, MSc., MIEEE, MCSE VE3ID/G4AJQ/VA3MCU
Amateur Radio, the origin of the open-source concept!
Skype: TILBURY2591
I’m working on a project, and I need to know the
age of various tape formats. For example when were 6250bpi 700’ 9-Track tapes or DC600A
cartridges introduced? Is there any good resource online that documents this? Wikipedia
is of some help, but the older you go, the spottier it is
Strictly speaking out of an orifice, I'd suggest that 9 track tapes in
NRZI and PE first came around with the IBM 2400 series tapes, GCR with
the 3400.
Prior to the S/360, tape drives were largely 7 track and used NRZI in
200, 556 and 800 bpi densities (IBM 700 series drives). Of course,
there are many outliers.
As far as QIC-24 (DC600A), the applicable standard dates from 1983.
https://www.qic.org/html/qicstan.html
FWIW,
--Chuck