CROS

Capacitor Read Only Storage

Note: ROS [Read Only Storage] is a generic term within the System/360 family. It is implemented differently (in terms of physical hardware) in different models. In the Model 65 - and several other models - tiny capacitors are used to represent the bits; 1s or 0s. This implementation is called CROS [Capacitor ROS]. On this page, as in the IBM documentation, the terms ROS and CROS are used interchangeably depending on the context.

Below is an illustration of the differences in ROS field (micro-order) structure between the standard and FAA Model 65s. It can be seen that 'spare' bits in the standard Model 65 have been allocated new functions in the FAA Model 65. It is significant to note that nothing has been taken away from the standard machine's ROS, functions have just been added.

CROS bit listings

CROS bit listings for the FAA Model 65. Click on the "QZXXX" links to view the listings. The third column in the listing, headed "CLD", gives the number of the Control Automation System (CAS) Logic Diagram (CLD) page the block appears on (e.g. QY051) and the 'grid reference' of the block on the page (e.g. N8). The main part of the page shows the actual bits (0 or 1) broken down into fields and parity bits. Note the only unused bit in each ROS word is the second bit (bit 01) which is set to 0 in every ROS word.

Bit listing for CROS plane 01 (0): QZ001 

Bit listing for CROS plane 02 (1): QZ011

Bit listing for CROS plane 03 (2): QZ021

Bit listing for CROS plane 04 (3): QZ031

Bit listing for CROS plane 05 (4): QZ041

Bit listing for CROS plane 06 (5): QZ051

Bit listing for CROS plane 07 (6): QZ061

Bit listing for CROS plane 08 (7): QZ071

Bit listing for CROS plane 09 (8): QZ081

Bit listing for CROS plane 10 (9): QZ091

Bit listing for CROS plane 11 (A): QZ101

Bit listing for CROS plane 12 (B): QZ111

Bit listing for CROS plane 13 (C): QZ121

Bit listing for CROS plane 14 (D): QZ131

Bit listing for CROS plane 15 (E): QZ141

Bit listing for CROS plane 16 (F): QZ151