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DEC PDP-8/S #3

PDP-8/S, S/N 537, Donated 5/11/2011
OMD8S, S/N 96
This rack-mount system came with an OMD8S Mounting assembly and control logic for DB8S and MC8S options; interconnections for ME8S. When you add the OMD8S to a PDP-8/S you move the 4096-word core memory from the 8/S chsssis to the OMD8S. You can install an MC8S Memory Extension and Control and additional 4096 word memory in the OMD8S to increase the total memory to 8192 words. With the OMD8S installed you can add up to three ME8S 8192-word memory mounting hardware (accomodated one or two MM8S 4096-word memory modules), to increase the total memory to 32768 words.
This OMD8S has the DB8S Data break facility installed. The DB8S is a primitive version of DMA and can be used to connect one DF32 and three DS32 32 KW fixed disk drives to the 8/S. The DF32 was available in a special version that could slow down the data transfers to a rate that the 8/S could handle. The 8/S is not fast enough to support the DECtapes that are common on other PDP-8 models.
The Rack mount PDP-8/S chassis.
The OMD8S chassis containing the 4096-word core memory and the DB8S data break facility.
An additional 4K of core memory can be installed with the MC8S option in the top left of the chassis.
Three additional ME8S 8192-word core memory chassis can be connected to the OMD8S for a total of 32768 words of core memory.