Noel wrote: > 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".
http://www.bitsavers.org/www.computer.museum.uq.edu.au/pdf/DEC-10-HMAA-D%20PDP-10%20KA10%20Central%20Processor%20Maintenance%20Manual%20Volume%20I.pdf p 1-1 (pdf pg 13) says the CPU options were: KE10 Extended Order Code (byte instructions) KT10 Memory Protection and Relocation KT10A Double Memory Protection and Relocation KM10 Fast Registers Elsewhere I have the note the the fast registers had 0.21 microsecond access time.
