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IBM360-30 Read Only Storage
January 29, 2018
By Jeff K.

The IBM360-30 uses Printed Card Capacitor storage for microcode.

The cards were created by printing Silver ink on Mylar:

Silver.jpg

Or etched copper:

Copper.jpg

304 cards make up the microcode. I scanned them all.

My procedure was to remove one card, clean it, scan it, and then replace it before removing the next card. My original thought was to clean the cards thoroughly using water, possibly with soap, as the machine was stored in a damp location. However, the cards turned out to be quite clean, and only required wiping. 

Scans were captured at 24-bit color, 600-bpi resolution. The captured area was 3.15″ x 7.25″, and saved as .BMP files (24MByte). I used different color backgrounds, and chose the sky-blue background as providing the best contrast for my eyes. Processing of the images used the Blue channel. Determining a threshold of hole/not hole was tricky, as there were two types of card, and each card had two areas to decode: the first 10 columns as card ID, and columns 11 through 70 for microcode data. Registration of the scans was quite consistent for row alignment, but column alignment was variable. Only one card needed adjustment vertically, but all card images were trimmed to align the first column. Data was decoded from the card images and stored in a card archive.

About the Author
Jeff K.
Vintage Hardware Restoration Engineer
As a kid, Jeff became interested in how machines work after reading Benny the Bulldozer by Edith Thatcher Hurd (1947). In high school, Jeff took his first computing classes, including a math class that taught him to plot a spirograph on a HP 91000B calculator. Jeff eventually enjoyed a thirty-five year career as a technician with Strobe Data, before joining LCM+L’s engineering team to work on the Xerox Sigma 9 mainframe computer. Today you can find Jeff tinkering away upstairs on the IBM 360/30.

He continues to plot spirographs on computers.
About the Author
Jeff K.
Vintage Hardware Restoration Engineer
As a kid, Jeff became interested in how machines work after reading Benny the Bulldozer by Edith Thatcher Hurd (1947). In high school, Jeff took his first computing classes, including a math class that taught him to plot a spirograph on a HP 91000B calculator. Jeff eventually enjoyed a thirty-five year career as a technician with Strobe Data, before joining LCM+L’s engineering team to work on the Xerox Sigma 9 mainframe computer. Today you can find Jeff tinkering away upstairs on the IBM 360/30.

He continues to plot spirographs on computers.

Category Tags
Restoration