DIY Q22 Backplane

[Radix]

OK, I need to take a break from this. I was having fun, happily running the system, editing/compiling/running FORTRAN code and my DK: device (DL1 on the RLV12 emulator SD card) got corrupted. I'm seeing multiple instances of ".FOR" extensions changed to ".FOP", ".OBJ" to ".OBH", and "SAV" to ".SAT" -- those are all the result of a single bit getting cleared (e.g., RADIX50 value of J is octal 12, H is octal 10). But there are other corruptions as well that aren't so simple (like a directory entry for a .COM file pointing to a FORTRAN file instead, though I suppose that could still be caused by a single bit error - I don't have any info on RT-11 disk format).

I have no idea where the problem is - my backplane, the RLV12 emulator, the SD card, the memory, the processor, the operating system.
I'm strongly doubt it's any of the latter 3 - the M8059 supports parity, so should report an error if it's dropping a bit, the processor still runs the operating system just fine, and RT-11 is very stable software.

I'll have to think about how to proceed...

RT11 might not be sysgened for parity RAM, I would run XXDP diags and VMSA?? for some (many) hours - I had something really similar with my PDP11 with faulty non-parity RAM a couple of years ago...

Also see if you can check the supplies at the backplane for stability..

Robin

 

[Steve Toner]

Oops! Yeah, I ran a sysgen for this system but I never installed it, so I'm running the default build that comes on the distribution disk...

However, I'm still going to take a break

 

[Steve Toner]

OK, getting back to this system...

The M8059 tested OK in another system, so I don't think that was the problem. I did build a new RLV12 emulator board and installed that. We'll see how things go...

Meanwhile, I was not content with a mere 256KB of RAM so installed a 1MN NS23C card in place of the M8059. The extra 768KB will make a nice RAM disk (VM device) and reduce the need to access the RLV12 emulator's SD card...

 

[F11ACP]

Program:

Hi, just out of curiosity, what was that program's exact output (to compare to what I'm getting on various simulators or VAX). Thx!

 

[Steve Toner]

3.141592653589796 on this machine and an 11/73. It gives a different, less correct, response on an 11/23 with M8188 (FPF11) floating point processor. That machine is currently out of service, so I can't give the exact result it prints, but I think it was something like 836 in the last 3 digits...

 

[F11ACP]

3.141592653589796

Awesome, thanks. Do you happen to have the iteration count, as well?

 

[Steve Toner]

262144 iterations. Fewer with the FPF11 (I think it probably secretly has one bit less resolution )

 

[F11ACP]

262144 iterations.

Thanks again, very much appreciated!