> From: Paul Koning > Some early machines, the PDP-6 I believe is an example, have > "registers" in the ISA but they actually correspond to specific parts > of main memory.
The PDP-6 and KA10 (basically a re-implementation of the PDP-6 architecture) both had cheapo versions where addresses 0-15 were in main memory, but also had an option for real registers, e.g. in the PDP-6: "The Type 162 Fast Memory Module contains 16 words with a 0.4 usecond cycle." The KA10 has a similar "fast memory option". Noel