3 Jun
2018
3 Jun
'18
10:34 a.m.
The 729 CE manual quotes 555 BPI. I?m not sure when it became 556.
http://bitsavers.trailing-edge.com/pdf/ibm/magtape/729/223-6845_729_CEman_1…
The IBM 728 was 248 BPI. Before that it was the nice round number 200 BPI.
I tried permutations of standard IPS and round number data rates and don?t see anything
that yields exactly 556BPI.
Tim
4 Jun
4 Jun
11:20 a.m.
From: Shoppa, Tim
Sent: Sunday, June 03, 2018 10:35 AM
The 729 CE manual quotes 555 BPI. I?m not sure when it
became 556.
The IBM 728 was 248 BPI. Before that it was the nice
round number 200 BPI.
I tried permutations of standard IPS and round number
data rates and don?t
see anything that yields exactly 556BPI.
Just to add to the mists and smoke and chaos:
For decades, I remembered the lowest density for magnetic tapes as 225 bits/in,
not 200. I have never been able to find the number "225" in any manual since
starting the project which became the museum 15 years ago (sob!), but it still
hangs around in my mind and pings whenever I see "200BPI" mentioned.
Anyone else ever encounter that?
Rich
Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computers: Museum + Labs
2245 1st Avenue S
Seattle, WA 98134
mailto:RichA at LivingComputers.org
http://www.LivingComputers.org/
2:15 p.m.
On 06/04/2018 11:20 AM, Rich Alderson via cctalk wrote:
For decades, I remembered the lowest density for
magnetic tapes as 225 bits/in,
not 200. I have never been able to find the number "225" in any manual since
starting the project which became the museum 15 years ago (sob!), but it still
hangs around in my mind and pings whenever I see "200BPI" mentioned.
Nope. I've seen 248 mentioned and I have period-specific tapes that are
declared to be 200 bpi on the label and then there's this:
http://www.digitalheritage.de/peripherals/cdc/604/604.htm
Note the density indicators on this panel from a CDC 604.
--Chuck
6 Jun
6 Jun
12:18 p.m.
Hi all,
thanks, Chuck, for pointing to my website with the 604 drive, but
it's currently offline as I am required to update the disclaimer part.
This is required, since in Europe,a new law for data protection was
introduced on Friday, 25th of May.
I plan to put the website back online this weekend.
All the best,
Pierre
-------------------------------------------------------------------------------
Pierre's collection of classic computers moved to: http://www.digitalheritage.de
Am Montag, 4. Juni 2018, 23:15:10 MESZ hat Chuck Guzis via cctalk <cctalk at
classiccmp.org> Folgendes geschrieben:
On 06/04/2018 11:20 AM, Rich Alderson via cctalk wrote:
For decades, I remembered the lowest density for
magnetic tapes as 225 bits/in,
not 200.? I have never been able to find the number "225" in any manual since
starting the project which became the museum 15 years ago (sob!), but it still
hangs around in my mind and pings whenever I see "200BPI" mentioned.
Nope.? I've seen 248 mentioned and I have period-specific tapes that are
declared to be 200 bpi on the label and then there's this:
http://www.digitalheritage.de/peripherals/cdc/604/604.htm
Note the density indicators on this panel from a CDC 604.
--Chuck
2174
days inactive
2177
days old
3 comments
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participants (4)
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