On Wed, Mar 4, 2015 at 4:23 PM, Stephen Lafferty <steve at tronola.com> wrote: Note that the schematic revision (CS) and the corresponding etch revision often do not match. A particular etch can have different levels of ECO corresponding to different schematic revisions, and a particular schematic revision might correspond to both an older etch with ECOs and a newer etc without ECOs (or with fewer ECOs). The schematic revision is supposed to be stamped on the board or handle, and updated if ECOs are applied in the field, but they're not always marked correctly. The field maintenance print sets often, but not always, have a table listing the correspondences.

On Wed, Mar 4, 2015 at 5:23 PM, Stephen Lafferty <steve at tronola.com> wrote: One small correction: M8340 Rev. D is compatible with M8341 Rev. C and earlier, from best I can tell from the DEC ECO Log. I don't think there were many changes between M8341 Rev. D and E. An M8341 Rev. C schematic would help to establish the differences between incompatible board sets. If anyone has a Rev. C (or earlier, even) and is willing to scan both sides, I can attempt to make a schematic. I'm working on that right now for the M8340 Rev. D. Right now, obvious differences between M8340 Rev. D and F are that two ICs have been dropped (both DEC 380s) and a 74H40 has been exchanged for a 74H11. I'm betting that the logic change there created the incompatibilities they mention. By the way, I did try running these boards in my 8/M; multiply seems to work fine, but divide returns the wrong answer. I didn't do any more testing after that (and instead read the ECO Log and found out the incompatibility reference). A big thanks to Steve, Chuck D., and Jack R. for their help in providing boards and pictures so far! Kyle