Recent content by mfeberhard

Most likely, you set the address on 8 switches, and the data on the other 8. (Which is which?) Programming is probably done with the Load switch, one byte at a time. The Step switch probably just increments the address. Note that the 1702 EPROM uses completely different voltages for data and...

My first assumption was that the disk was not centering properly, and so I spent some time and effort studying how the cone centers the disk onto the spindle hub. The short answer is that the disk is centered on the hub correctly, even on a wobbling spindle hub. I used a straightedge as a...

That's what I first suspected. I inspected the cone assembly, and carefully studied how it aligned the disk on the spindle. It was perfect. But holding a straightedge to the hub, I could see that it was indeed very obviously wobbling. I didn't try to get an exact measurement, but I'd estimate...

I posted this in the "What I Did on my PDP8" thread, but this seems like a better place. I've been restoring an RX02 drive on my PDP8e, which had quite a few issued when I started. In order to align the drive (track alignment, head lifter adjustment, track 0 sensor, and index sensor), I wrote a...

I've been restoring an RX02 drive on my PDP8e, which had quite a few issued when I started. In order to align the drive (track alignment, head lifter adjustment, track 0 sensor, and index sensor), I wrote a pretty useful program, called RX8ALIGN. This program lets you select a drive, seek any...

Yes. Also the ME27000 and a few other such things :)

Thanks for the feedback! Yes, I would prefer to keep it period appropriate, though I might settle for something else in the short term so that I can begin debugging the CPU. (I've already repaired the power supplies in the CPU chassis and the expansion chassis.) So ideally yes - an MM11-E or -F...

I'm looking for core memory for my PDP11/20, including especially the required backplane. (This machine delivers power to the backplane sections with paddle-boards, not with the Molex connectors on later Unibus machines.) If you have any parts for Unibus core memory that's compatible with an old...

I've just found (and fixed) a bug in my AMON monitor. This bug will cause the AL command (for loading "absolute Binary" files, such as MITS Basic) to fail if the console port is also the transfer port. This bug exists in AMON versions 2.8, 2.9, and 3.0. Here is AMON 3.1, which corrects this...