On Wed, Sep 7, 2016 at 8:35 AM, Noel Chiappa <j...@mercury.lcs.mit.edu> wrote: > > From: Ethan Dicks > > > What's happening now . is when I change one location .. it > > echoes across multiple locations... > > ... > > 1) Depositing any value is echoed 000020 later. > > ... > > Does this sound like a dodgy CPU, dodgy RAM or both? > > It could be either. One possible cause of the symptoms you're seeing is that > address line A04 on the bus is being held to one value (high or low) by > something on the bus, so that whether the CPU tries to set it to 0 or 1, it > has no effect. Also, of course, there could be some fault in the CPU, so that > when it tries to do something with address 0, it gets 020 (or vice versa). > And similarly for the memory. > > I'd try to write a small (two instruction) loop that sets that address line > high/low (e.g.: > > 5037 CLR @#1020 > 1020 > 775 BR .-4 > > and look and see if that address bit is flickering on/off on the UA11 (it will > be on, but dully; constant assertion is bright on, constant de-assertion is > full off). If so, the problem is almost certainly in the memory; if not, it > could be either.
Once I get the console ODT to show up again, I will try that. Something appears to have died while I was powered-on and testing last night and now, the run light goes off right away after hitting boot, and I don't see the address lines or the data lines flickering. > > 2) Setting D10 in location 000000 results in D10 set in all the > > locations > > Sorry, didn't follow that? Did you mean that if you store 02000 in location > 0, all other locations now report the 02000 bit set? Only 04000, but, yes. If I set that bit in location 0, or other locations, it gets set in all locations. If I clear that bit, it clears. I won't be able to enter 5037 / 1020 / 775... it will read back as 1037 / 1020 / 775 based on my previous work (depositing 1020 will "turn" 5037 to 1037...) -ethan