PDP-11/83

 

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I now have an 11/83 with 4 megs of RAM. I traded a resurrected RD54 for the CPU and one memory board, and bought the other memory board for $8 on eBay. Someone gave me an 11/34 system that I really didn't have room for, so I traded it for a BA123 chassis. I traded an old DSD-880 8" Winchester disk subsystem for the SCSI card, and bought the rest off eBay. Total cost: maybe $200~$300 cash plus some tradeable junk.

This is the main machine now, which unfortunately doesn't get used much because I'm usually working on an 11/53 or 11/23 for someone else. Here is a description:

bulletBA123 chassis from an old microVAX
bulletKDJ11-BF 11/83 CPU, 18 MHz
bulletMSV11-JE 2 meg ECC ram cards (2)
bulletEmulex UC07 SCSI hard drive controller
bulletRQDX3 MFM hard drive controller
bullet ST410800N 10 gig SCSI hard drives (2)
bulletRD54 150 meg hard drives (2) (these come and go since they mainly come here to be set up for other computers)
bulletRX50 floppy (not working yet)
bulletDELQA Ethernet card

The OS is 2.11BSD networking. It can get on the Internet and automatically sets its clock via the home network gateway.

Promises: someday I will document the following:

bulletjumper settings for KDJ11-BF CPU (when I find them myself).
bulletjumper settings for MSV11-JE
bulletwhere/how to get the parts
bullethow to set up the machine
bullethow to set up 2.11BSD, particularly the networking, for this platform

Until then, if you need info desperately, email me: moc.liamtoh@lhadgnerj (turn it backwards).

Performance

I expected the 11/83 to be much faster than the 11/53. I found that it takes the 11/53 about 20% longer than the 11/83 to rebuilt UNIX. On some tasks, such as diff'ing two directories, the 11/53 is faster. They both have the same CPU chip, and both run at 18 MHz. The difference is in the memory architecture. The 11/83 has a fast cache on board, and accesses memory via a dedicated PMI bus. The 11/53 has no cache, but all its memory is on-board. So if a program can take advantage of caching, it would run faster on the 11/83. If a program does something that a cache can't help with, the 11/53 might be faster.

Where to get the parts

The CPU and RAM cards show up on eBay every so often and sell for around $50. You can find the MSV11-JE listed with surplus dealers for affordable prices (under $75 maybe). Expect to pay $15~$20 for an RQDX3 on eBay. You'll need one for the floppy at least. You can easily get a DESQA (electrically the same as DELQA) for $20 and reconstruct it for the BA123. A real DELQA with the cab kit is harder to find but still won't drive you broke.

Hard drives are always the most difficult part of a PDP-11 to find.  The rules seem to be:

bulletMFM:
bullet$200 and up for the drive (mainly RD54, XT2190)
bullet$25 for the controller (mainly RQDX3)
bulletreliable drives are hard to find, they are all 15+ years old
bulletmax size is 150 meg
bulletSCSI:
bullet$200 and up for the controller, and they are hard to find
bullet$10~$25 for the drive, very easy to find
bulletcontrollers are compatible with recently built, still reliable drives
bulletalmost any SCSI hard drive is larger that you'll ever be be able to use on a PDP-11.
bulletmax useable drive space for BSD is something like 7 gig (1 gig per partition, plus one partition for swap)
bulletESDI: 
bullet$50 for the drive, see eBay or legacy drive suppliers, there seems to be enough to meet the low demand
bullet$50 for controllers, but they are rare
bulletthe typical ESDI drive seems to be 350 to 700 megs
bulletESDI drives were built more recently, and therefore many should still be in good shape

Until someone proves otherwise, I would suggest staying away from any ESDI or other drive manufactured by Micropolis. They made the infamous DEC RD53, which all died a horrible premature death. I've read that the foam bumper for the access mechanism turns to sticky goo and glues the heads in the home position. The voice coil is not strong enough to break it free. I noticed that my old IBM PC ESDI drives of the same vintage also did this. For a while I could get one of them to come up by banging the drive against the PC chassis  to knock the head mechanism free (while it was running, held in my hand at the end of the cables), but this is not a recommended long term solution. You'll find that a 700 meg Micropolis ESDI drive is sold by dealers for about half the price of a 300 or 600 meg Seagate drive -- stay away from it.

Early in 2003 there was a spate of RD54's on eBay going for an average of around $175 each. Before this there were a few SCSI controllers going for $200 and up. I may have a couple of spare useable RD54s still, but intend to sell them off.

If you can find a SCSI board for $200, pay it quickly and cheerfully. Make sure that it is an MSCP SCSI controller for disks. There is a VAX board called the KZQSA that is non-MSCP which sells for around $40. You can't use this with a PDP-11, nor with any VAX operating system other than DEC's own VMS or Ultrix.

I don't know of a good source for cabinets, except finding them locally, because DEC boxes use a lot of heavy steel. You can use a BA23 (with or without pedestal), BA123, or BA213 (typically from a DECserver 500 or 550).

Shipping cabinets is difficult. Almost every large cabinet (BA23 , BA213) that I've seen handled by UPS or FedEx has been seriously damaged. They don't seem to be set up to handle things that size, and eBay shippers don't know how to pack them right. It's hard to find a good box to fit a BA23. Foam peanuts are not adequate packing for a 60 pound DEC chassis. The peanuts shift and the single wall box turns into a shapeless round blob like an giant stuffed animal wrapped round with packing tape. And inside -- Oh sorrow...

5/24/03

 

Last modified: December 31, 2009