I have posed this question to the 8lovers list, and folks seemed to misunderstand. So let me try here. I believe sometime in the late 70s, maybe as late as 1980, a prof associated with UMass wrote a paper describing an extension of the PDP8 called 8/X or 8X. THIS IS NOT the Pre Nova/DG machine but a completely different concept. THis is not the FPGA pdp8 implmetaton that also has an X in the name. I believe, my memory is fuzzy, that it was a prof nnmed Stone or Stoner (perhaps Harold S) who lead the effort and had his name on the paper. My fuzzy recollection was this was PDP8 with a Cache, an extension of the instruction set, maybe to 24bits, and full compatibility with 8/e-8/a. I recall the spec citing a 10mhz (100NS) cycle time. some sort of start up setting that would make it 8 mode or X mode on start up, don't recall if it could switch modes while running. I had a copy of the papers some where and it is misplaced hiding on one of my computers and I am bout to pull out my BigMac that might have the data in it. THanks for any hints as to the online location, Again, this is NOT the pdpX concept that led to the DG or the FPGA system or the spartan 3 based system, it is just a concept paper. Thanks bob