On 17 Dec 2008 at 13:25, Tim McNerney wrote: The PPS-4 is similar to the 4004 in that there is a family of chips which work together with a highly-specific set of control signals and bus cycle. The PPS-4/2 version could produce a minimal system in two chips: processor and combo mask-ROM/RAM/IO. As with the 4004 it was directed towards embedded systems and isn't so amenable to use as a general-purpose system. There was a later PPS-4/1 single-chip version. I don't know how popular this stuff was but I wonder if there aren't more PPS-4 systems buried in equipment and appliances from the period than is commonly known. (I have wondered, for example, what the 70's-era Amana Radarange microwave ovens used for control.) I suspect a version of the -4 may have been used in some Victor desktop calculators (1800,1900 series) ca 1972, as the chipset in these calcs is made by Rockwell and looks much like the PPS-4 chipset. The PPS-8 receives a chapter in Osborne's 1976 "An Introduction to Microcomputers - Vol II - Some Real Products". The bus cycles are quite similar so it would appear the -8 was based on the -4 to quite a degree. (We discussed the PPS-4 and -8 on the list a year or two ago, there should be some other mention in the archives.)