PDP-8M

The original PDP-8 model (informally known as a "Straight-8") was the a 12-bit system and became first successful commercial minicomputer, produced by DEC. Over 50,000 systems were sold, starting in 1965 when it was first introduced. The PDP-8 model used diode–transistor logic packaged on flip chip cards and was about the size of a small household refrigerator.

This was followed in 1966 by the PDP-8/S, available in desktop and rack-mount models. Using a one-bit serial arithmetic logic unit (ALU) implementation, allowed the PDP-8/S to be smaller, less expensive and slower than the original PDP-8. The PDP-8/S was about 20% of the cost and about 10% of the performance of the PDP-8.[9] The only mass storage peripheral available for the PDP-8/S was the DF32 disk.

Later systems (the PDP-8/I and /L, the PDP-8/E, /F, and /M, and the PDP-8/A) returned to a faster, fully parallel implementation but use much less costly transistor-transistor logic (TTL) MSI logic. Most surviving PDP-8s are from this era. The PDP-8/E is common, and well-regarded because so many types of I/O devices were available for it. It was often configured as a general-purpose computer. This model, the PDP-8/M, was indeed a faster, smaller, and less expensive version of the original.