building a PDP11 from the things you find at home

Jerome Fine replies: Thanks for your comment - I had a good laugh. Also with a bit of tongue in cheek, a reply ... Yep! It includes those nerds who need to hear the screech of a disk drive bearing gone bad (the RD53 whine is about the best) and the broken back achieved while lifting an RA81. It also includes those software nuts like myself who will work for a few months to reduce the size of a program that almost no one uses anymore or output an error message than can be understood to a user who does not exist. I will admit that on occasion, I do delight in using VERY OLD hardware. About 2 years ago, I needed to transfer some data to a real DECTape II on a real TU-58 tape drive. However, the FINAL goal was to connect the TU-58 external tape drive to a PC running the emulator for the PDP-11. I don't know if anyone still uses a real DEC TU-58, but it is still just as slow on a PDP-11/93 as it was on an LSI-11/2, so of course, it is no faster on a Pentium 166 MMX. In any case, I finally got the external TU-58 connected again first the the real PDP-11 and then to the PC on a COM2: port and copied the files. Then I was able to find a very old version of V 3.0B of RT-11 that was on a TU-58 tape that still worked. WOW!! After 2 minutes it actually booted RT-11. Worked just fine. Then, just to put the icing on the cake, I copied the files from a V5.04G of RT-11 (that I had enhanced to be Y2K compliant) to the TU-58 and was again able to boot RT-11 (after the customary 2 minutes). Now that was a thrill - running a 25 year old tape drive first with a 25 year old version of the RT-11 operating system on a Pentium 166 MMX (using the emulator of course), and second with a10 year old version of the RT-11 operating system which had been Y2K enhanced so that I could use dates after 1999. Actually, I think both the hardware and software goals that we have are crazy, but since we all seem to enjoy ourselves and I know of no law that is being broken that will need to be invoked to slowly lower us feet first into molten iron, it seems harmless enough. Aside from the fact that I seem to need to start the emulator from a boot or it runs of of memory, I find that M$-Windoze does not seem to interfere very much even though I dislike admitting that fact. Of course, I also can't run anything else at the same time. On the other hand, I use the same 1 GByte ESDI drives on the PC as on the real PDP-11, each with its own fan to keep it cool. And the front loading tape drive on the PDP-11 is too heavy by far (even heavier than an RL02 drive) to lift into the rack, so I will have to have someone help me take it to the curb. Plus I have not had an occasion to read a 9-track tape drive for the last 10 years since the TK50 became a viable distribution media - not that I would EVER consider the TK50 to be a successful backup drive/media - although a TK70 at 256 MBytes finally seems acceptable. Well, when you get to be my age (I just turned 63), you may sing a different tune. This weekend, I just finished nursing a very sore back into a reasonable disposition after working with a BA23 (NOTE: not the BA123 just the BA23) system. I had a bad DRV11 (M7941) module that stopped the system from booting. My first impression was that the PSU might be gone, so I transferred just the memory to a different BA23 that I hoped was working. That worked with an M8090, so I added a few more boards including the disk drive. When all that worked, I transferred back to the original BA23 and it still worked. So I swapped in the M8192 and the boot ROM board and finally the last 4 dual boards which ended up crashing the system again. Took out the last 4 dual boards at which point it was OK and started adding them one at a time. Viola!!! One board to go - the M7941 and it started crashing again. Out and replace with an M9047 - bus grant card - AND it works!!!!!! FINALLY!!!! Anyone have a spare M7941 they want to sell? I also will need those zero ohm resistors set to a non-standard CSR/VECTOR!! Plus, I also would like to buy a TU-58 external tape drive - does anyone want to swap a dozen tapes for an external TU-58 tape drive? I will also consider buying it. I also will consider buying a single 4 MByte PMI memory board made by Christlen. Better still, maybe an 11/93 or an M100 from Mentec. I am hoping to cure my 7 quad board problem in the BA123 box with the ESDI hard disk drives. If I can put 8 quad boards into a BA23, then that will mean that it is the BA123 that is bad. So back to swapping boards again. Sincerely yours, Jerome Fine