14 Dec
2007
14 Dec
'07
11:25 a.m.
On Fri, 14 Dec 2007, jim s wrote:
Also all the drums I ever saw had a sort of flying
head with a horizontal
head in a hole with a small spring mechanism that would hold it in position.
I don't if the head normally was out of contact with the drum while the head
was stopped and was then sucked in, or if it landed and was pushed back, but
that whole affair was delicate as well.
Just for reference, here's some information about the drums used in the
SAGE (AN/FSQ-7) system:
Length: 12.6 inches
Diameter: 10.7 inches
Weight: 85 lbs
Speed: 2914 RPM
Recording Surface: nickel-cobalt alloy
Word Length: 32 bits (typically, plus various control and parity bits)
The heads were fixed, on 6 pairs of mounting bars, with a critical air
gap between the head the drum surface. The Q7 drums had two sets of
heads to support simultaneous r/w operations between the computer and
drums, and outside equipment (radar info, xtel, etc).
Here's a picture from the Computer History Museum:
http://sturgeon.css.psu.edu/~mloewen/Q7/CHDrum.jpg
... and a very small picture of r/w head:
http://sturgeon.css.psu.edu/~mloewen/Q7/parts.gif
The head is in the lower right hand corner.
Specifics were taken from pp 125-131 of the "Theory of Programming"
T.O.:
http://www.bitsavers.org/pdf/ibm/sage/31P2-2FSQ7-112_SagePgmNov56.pdf
Mike Loewen mloewen at cpumagic.scol.pa.us
Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
