IBM 5280 Technical Newsletter page 157

403
FEATURE MAIN STORAGE CARD (A-B5)
The diskette/main MPU card (303) contains 32K bytes
or 64K bytes of main storage. Additional storage may
be located on an optional 16K, 32K, or 64K byte main
storage card. This optional storage is added in card
location B 5.
The storage capacity of each feature main storage card is
indicated by a color marked on the end of the card. The
blue code indicates a 16K byte card, the orange code
indicates a 32K byte card, and the red code indicates a
64K byte card.
The switches on the storage card must be set to indicate
the starting address of the storage on that card. I f the
diskette/main MPU card contains the first 32K bytes of
main storage, only switch 5 (32K byte) must be set to
the On position. If the diskette/main MPU card contains
the first 64K bytes of main storage, only switch 4 (64K
byte) must be set to the On position. See (303) to
determine which card is used.
All other switches must be set to the Off pOSition.
The MDls for main storage (0520 and 0530) start testing
at 32K and test through the end of storage. (The
power-on checkout tests the first 32K bytes of main
storage.) If the diskette/main MPU card (303) has a red
color code (64K) replace the MPU card if the failing
address is less than 64K.
On
11121314151617181
Off
/
Color
Code
•
TP01
403
Page of SY31-0600-1
As updated September 7, 1981
By TN L SN20-9656
If the card has a removable plastic cover over the switches,
remove the cover to change the settings of the switches.
After you have changed the settings of the switches, rein-
stall the cover.
If the card does not have a removable plastic cover over the
switches, see the following illustration for an example of how
to set the switches. Ignore the red indicator and set the
switches to the desired setting.
Main Storage and Main MPU 59