MACHINE CONFIGURATION HAD NO PRINTER, JUST READER AND INTERNAL DISK
After surveying the cards installed in the machine it was clear that it was connected to an IBM 1442 reader/punch but did not have cards for the 2501 reader, the 1132 printer nor the SAC feature needed to attach the 1133 Multiplexer which controls the 1403 printer. This was odd because DMS 2, the controlling software for the system, expects a reader and a printer.
LOOKING AT PERIPHERAL CONNECTORS INITIALLY CONFUSED ME
The connector panel in the 1130 has assigned locations for all the peripherals. A few are mutually exclusive, for example the 2501 card reader cannot coexist with a 1231 optical mark reader because they are both assigned to connector slot PC8.
When I saw the connector at PC8 and knew the machine did not have cards to support a 2501, I leaped to the conclusion that it had a 1231 configured. When I looked at all the card compartments I found no cards in the slots that support 1231.
CARDS IN COMPARTMENT A-A1 THAT ARE NOT ON STANDARD ALDS
The mystery grew when I spotted quite a few cards in the bottom half of compartment A-A1 which should have empty slots. These are wired to the connector at PC8. Other cards in the machine told me that it had support added for cycle stealing levels 2 or 3 and some additional memory addressing logic. Finally, I found a clue, a card that was identified as part of the OEM Channel RPQ.
FOUND A MANUAL FOR OEM CHANNEL RPQ
I discovered a manual which clarifies that the OEM Channel RPQ is a feature that is installed to give third party peripheral makers a sanctioned way to attach their box to the 1130. It provides some of the functionality of the Storage Access Channel (SAC) feature without needing that more complex interface.
It is my working assumption that this RPQ feature was used to connect a line printer built by a different computer or peripheral manufacturer. The inclusion of cycle steal support is consistent with this idea. I see this an alternative to using the IBM 1403 printer.
PRINTERS OFFERED ON THE 1130
The 1132 printer is a low cost and relatively slow machine, using refurbished print engines from IBM 407 accounting machines, that burns a lot of CPU cycles to print. It is directly connected to the 1130 if the controller logic is configured into the system and is powered through the 1130 system.
The 1403 printer is a much faster machine but has extensive controller logic that sits in the IBM 1133 Multiplexer box, a kind of expansion box for 1130 systems. It requires less CPU support to print lines that the 1132. To install a 1403, one must buy the SAC feature for the 1130, buy an 1133 box and then buy the 1403. In addition to the cost and substantial extra floor area, it requires three phase AC. In most cases, an IBM 1130 system is powered by single phase power.
If a third party offered a line printer that had the speed and print quality of a 1403, but only required the OEM Channel RPQ to be bought for the 1130, it would avoid the floor space and three phase AC burdens of the IBM solution. I knew of other third party printers that required the SAC feature, but this RPQ feature offered a simpler and presumably cheaper route to connect a printer.
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