J. Peterson wrote: The Tektronix 4081 used an OEM Interdata 7/16 CPU board set. The disk drives were, IIRC, made by Wangco (a different company than Wang Laboratories). The drives had one fixed platter, and one removable platter, like an RK05F, but definitely different. Can't remember the exact capacity, but 10MB per-platter seems to ring a bell. Most of the systems I worked with had two of these drives. They used a disk cartridge that was similar to that used in a DEC RL01/RL02. The display wasn't driven "directly" by the CPU. There was a secondary graphics processor (designed by Tektronix, using AMD bit-slice technology, IIRC) that interpreted a display list placed into a movable segment of main memory. The CRT had write-through capability, and due to the power of the display list processor, you could do pretty darned good dynamic vector graphics with the thing. The backplane of the machine was Tek-designed, but general bus structure followed the Interdata model. Our group had a hardware engineer in it, who designed a RAMDisk that sat on the bus and used DMA to transfer back and forth between main memory. The bus was rather weird, and they had a heck of a time (even with help from the 4081 group) getting the board to talk. Once it worked, some hacks were made to the OS so that swapping (it was not a VM operating system) would be done to the RAMDisk which really sped things up. The OS and applications were also modified to store temporary files out on the RAMDisk. The OS was indeed called GOS, and was very similar to RT-11. From a programmers standpoint, the Interdata CPU was much more "IBM"-360-like than "DEC PDP-11"-like. I worked for a group within Tektronix called "CAD Development", which was an internal group that designed and wrote CAD software for Tektronix engineering use. We had a couple of 4081's in the group. They had written software for the 4081 that did a respectable job of schematic capture and circuit board design (no auto-route though...that job was left to the Control Data Cyber 73 and an in-house developed routing package called "PIRATE" (no connotation -- the routing software was original), written mostly in Fortran 77 on the Cyber. The 4081 could also generate artwork tapes for a Gerber photoplotter, as well as NC tapes for circuit board drilling/routing. There was a Pascal compiler for the 4081 that I ended up writing some code in. I never cared much for Pascal, but it worked, and it was a lot more productive than writing in assembly (which I also did some of). The disk drives were mounted in the base of the cabinet, and were prone to collecting all kinds of dust and fuzz, which, if not serviced regularly, would inevitably lead to disk crashes. Fortunately, the removable disk seemed more prone the crashes than the fixed disk (makes sense), but when the fixed disk crashed, it was pretty ugly. The machine had a ROM bootloader that allowed booting from a 4051-like cartrige magtape drive, or disk. Installing the OS took a LONG time interface to some kind of 9-Track magtape drive (reel-to-reel), and may have been bootable from said device. I know of no currently existing 4081's, but who knows what may be out there. It was definitely an interesting machine. I also heard the rumor that the machine was indeed a pet project of a son of some very-high-ranking Tektronix executive. Can't substantiate it, though. The Tektronix 4081 was used to generate the vector graphics for film of the full-screen graphics used in the original "Battlestar Galactica" TV show. The 4051's with the write-through modification were not fast enough (even when coded in machine code) to generate complex enough graphics, which is why the 4081 was used, because its display list processor made much more complex refreshed raster graphics possible. The 4081 was not actually used on-set, the on-set computers were Tek 4051's. Along with the 4051's there were wall-fulls TM-500 test equipment. Rick Bensene Tektronix Employee from 6/1977 through 9/1990 The Old Calculator Web Museum http://oldcalculatormuseum.com