Chuck Guzis wrote:
Did some of the S/360 machines use ferrite ROM for
stores? 360/40 perhaps? I believe some also used capacitive ROM
The three ROS (Read Only Storage) technologies developed for the
original System/360 processors were:
CCROS - Card Capacitor Read Only Storage - used etched metalized IBM
cards, either paper or mylar. Programmed using a normal card punch.
Used in 360/30. 750 ns cycle time.
BCROS - Balanced Capacitor Read Only Storage - similar but used two
capacitors per bit for better SNR and higher speed, and did not use a
normal card punch. Used in 360/65, with 90 ns access time and 200 ns
TROS - Transformer Read Only Storage - similar in operation to core rope
memory. Used mylar film tapes with metalization that either passed
between or around square holes for each of the transformer cores. Used
in 360/20 and 360/40. 240 ns access time, 625 ns cycle time. Based on
T.L. Dimond's "Dimond ring" transformer read-only storage first
described in 1951.
"No. 5 Crossbar AMA Translator," T. L. Dimond, Bell Laboratories Record
Volume 29 Number 2 pp.62-68, February 1951
"Card Capacitor - A Semipermanent, Read Only Memory", H.R. Foglia, W.L.
McDermid, H.E. Petersen, IBM Journal of Research and Development, Volume
5 Issue 1 pp. 67-68, January 1961
"Printed Cards for the Card Capacitor Memory", J.W. Haskell, IBM Journal
of Research and Development, Volume 6 Issue 4 pp. 462-463, October 1962
"The Design of Transformer (Dimond Ring) Read Only Stores", D.M. Taub,
B.W. Kington, IBM Journal of Research and Development, Volume 8 Issue 4
pp. 443-459, September 1964
"Design of a Printed Card Capacitor Read-Only Store", J.W. Haskell, IBM
Journal of Research and Development, Volume 10 Issue 2 pp. 142-157,
"The 'Braid' Transformer Memory", W.H. Aldrich, R.L. Alonso, IEEE
Transactions on Electronic Computers Volume 15 Issue 4 pp. 502-508,
"A Balanced Capacitor Read-Only Storage", S. A. Abbas, J. K. Ayling, C.
E. Gifford, R. G. Gladu, T. C. Kwei, W. J. Taren, IBM Journal of
Research and Development, Volume 12 Issue 4 pp. 307-317, July 1968
_IBM's 360 and Early 370 Systems_, E.W. Pugh, L.R. Johnson, J.H. Palmer,
MIT Press 1991.