I think you probably mean the CYBER 173 PPU--the CYBER 7x PPUs were essentially unchanged from the 6x00 series. 1 usec. cycle time. The character generator, IIRC, was an interesting array of LRC circuits, with the character size varied by simply increasing the amplitude of the drive waveform. This led to odd-shaped large characters. Chess was an oddball program. It was possible for a user program to request control of the display from the operator. There were two ways to do this. The first was to write your own display driver and request the display channel from DSD (DSD monitored R.RCH and R.DCH requests). An early version of chess I saw used a driver called (I think) CHD for this. There was also what was called the "T" display in DSD. This was a display mode that allowed a user-mode CP program provide a list of display directions in CM to be read by DSD. One of the directions was "jump", so the user program could allow DSD to regenerate the display without having to made additional system requests (which would have been too slow). I saw a later version of CHESS that used this method. The restriction on the T display was that it could generate a display for one screen or the other, but not both simultaneously. There was a very popular "programmer's display" driver called DIS that could attach to a control point and allow for job control entry, exchange package display, and numerous dump formats as well as a disassembler and CP breakpoint. There was a keypunch simulator called O26 (note the alpha "o") to allow the enterprising operator or programmer to generate a file of card images. A very expensive keypunch, indeed. KRONOS was a direct descendent of MACE, an alternative OS for the 6x00 written largely by Dave Callender and Greg Mansfield as a bootleg project at Arden Hills. Greg and Dave would visit the QA floor and cable together a system to do development on late at night, after the daytime shift had gone home. (MACE, if I remember correctly, stood for "Mansfield's answer to Customer Engineering". The "eye" display was part of every CE's deadstart (not "coldstart") tape. The "official" OS for the 6000 series was SCOPE--a system that was located largely in the PPUs, and pretty much oriented toward batch processing. Pat might want to investigate Dave and Greg's contribution to the OS that Purdue ran on their 6500 in the late 60's. I seem to recall that it was largely MACE with a lot of OS functionality moved into the CPMTR portion. A cultural war broke out in CDC over the two systems. SCOPE was pretty much a west coast Sunnyvale operation and KRONOS (i.e. enhanced MACE) an Arden Hills affair. Things really got pitched when PLATO elected to use KRONOS instead of SCOPE. The solution was to offer both as renamed entities. SCOPE 3.4 was followed by NOS/BE 1.0 (BE for batch environment) and KRONOS became NOS 1.0. A lousy move on the part of management, in my opinion and a huge duplication of resources. I have no particular ax to grind here, as I was Sunnyvale Ops, but Greg was a good friend, too. This doesn't include the "special" operating systems such as TCM, Zodiac, Rover, etc. One very positive thing that I can say about MACE was that Dave authored a set of fairly straightforward coding standards and adhered to them. So MACE systems code was easy to read; SCOPE was an agglutinative affiar with no particular coding standard being used anywhere. The 73 was basically a 6400 with added goo, such as the Compare/Move Unit; the 74 was basically a 6600 (wherein a CMU was not possible). There was a Cyber 72, which was a slowed-down (via jumper) 6400. The Cyber 76 was the follow-on to the 7600. This is from recollection, but I'm pretty sure that I'm very close. The Cyber 7x's had the fake wood-and-blue-glass look, while the 6000 series was dark grey and beige-ish. You had an unusual shop. At Sunnyvale, deadstart was almost always Bryant disk, to a big 808 (4-spindle hydraulic positioner, bit- parallel drive) to one of the "little" 844 removable pack drives. I know--more than anyone asked for. But questions about old iron are getting less frequent. Cheers, Chuck