Jerome Fine replies: Not a problem. The M8190 will operate in both ABAB and ABCD backplanes. I have successfully used an M8190 (a quad board) with a 4 MB memory board (also a quad board) in a VT103 backplane that had been upgraded to 22 bits. Note that since the VT103 backplane is ABAB on all 4 slots, it is not possible to use PMI memory as PMI memory. The PMI memory can, of course, be used as ordinary memory. I have heard that it is possible to alter the first 2 ABAB slots to be ABCD so that PMI memory can be used - or a Micro Vax II can be used. No details are available. A diagram would be helpful to identify the required points on the backplane. By the way, I stated (incorrectly) that 16 solder points are needed. Actually, 32 solder points are required, 2 for each slot (both AB and AB on each slot) and 4 slots and 4 address lines for a total of 8 solder points per wire and 4 wires. Lead based solder is needed for this very old backplane. Sincerely yours, Jerome Fine

Glen Slick wrote: So forgive my inexperience here -- but just to make sure I'm understanding the changes I need to make -- is all that's necessary just wiring up the address lines (18-21) from slot 1, to slot 2, to slot 3, to slot 4? Also, just to satisfy my curiosity -- it's been mentioned by several people that lead-based solder is necessary -- why is this? (I think I have a spool of it somewhere that I liberated from my grandfather's basement some years back, but I'll have to dig it up...) Thanks! Josh

Ethan Dicks wrote: I highly recommend 63/37 over 60/40. I find it easer to work with. Peace... Sridhar

Ethan Dicks wrote: Oh no, that's not what I'm saying at all. It's just that, if I'm going to be buying lead solder, I'll buy 63/37 every time. Peace... Sridhar

Diane Bruce wrote: It's not the lower melting point. It's that the mixture is eutectic. Peace... Sridhar

On 29 Dec 2008 at 8:57, Sridhar Ayengar wrote: There's a lot of misconception about what solder alloys are really about. The characteristics of various tin/lead ratios are very useful. I work a lot soldering sheet brass. Normally, I work with 50/50 alloy because of its large plastic range and its ability to fill gaps and be tooled while cooling. But if I'm working with something that requires a joint to solidify almost immediately from the liquid state (eutectic), it'll be a 63/37 alloy. Melting point isn't a major issue as I'm working with an acetylene torch. 60/40 gives you a bit of plastic time before solidifying, but not much. If I were soldering PCBs, I'd want the eutectic alloy--liquid or solid, with virtually no plastic phase in between. Plumbers and radiator repair shops use the 50/50 alloy because it can be tooled while cooling. (In theory, the term should be "plumbers used to use" since lead-bearing solder for plumbing now violates code in the USA. But I've yet to see a plumber who doesn't keep a couple of rolls of 50/50 squirreled away for the tough jobs). The tradeoff is that the workpiece must be solidly clamped or otherwise fixed so that it doesn't move while the solder is solidifying. This control of state-change characteristics is one thing for me that sets lead-bearing solders apart from the RoHS pack. Cheers, Chuck

Sridhar Ayengar wrote: I had the dubious distinction of being a "Certified Solder Operator" for TI's Lubbock, TX plant (in, what, '82?). Although the training I got there spoiled me forever in some ways, it's been invaluable over the years. One of the things that stuck was the "true purpose" of eutectic solder. We always used 60/40 for original or initial soldering, and eutectic for repairs or "oversolders". If you have a good iron and a good eye (or, these days, good Optivisor), the flow-point difference allows doing new work without disturbing old joints. Doc

Very helpful - thank you! Sincerely yours, Jerome Fine obtained by replacing the four characters preceding the 'at' with the four digits of the current year.

[Snip] Sorry about the subject line - my son modifies it when his server thinks it is something suspect.

Thanks for all the good advice (from everyone) on this thread. I need to wander out and find some good wirewrap wire & the appropriate solder and I'll let you know how I fare with the solder fest :). Josh Tony Duell wrote:

Since the memory is part of the PDP-11/93, probably the total on the 5 amps is reasonable for the VT103 power supply. I have a PDP-11/93 manual somewhere, but not handy at the moment. Al Kossow probably has the manual available.

Jerome Fine replies: Glad to know that my appraisal of your ability to solder was accurate. I figured that dividing my time by about 100 would be a good estimate. As far I my experience is worth, the upgrade to a 22 bit backplane with the version DEC provides in the VT103 works VERY well. I watched over at least 6 VT103s having the modification and all responded as expected. I also tested each point on the backplane before they were soldered and all points showed an open circuit to everything else. And as final confirmation, the pdf should confirm that the 4 address points in each AB portion of the backplane are not connected to anything else. The really cool reason to use a VT103 is that a hard drive can be placed right under the CRT. For someone who does not look closely, the VT103 will look identical to a normal VT100. Thus, when the VT103 is powered up and boots into one of the PDP-11 operating systems, the look of surprise is quite evident when they are told there are a pair of small monkeys inside who are answering the responses typed into the keyboard. :-) The one problem of using the VT103 is that the power supply is really too limited, although with only 4 slots, not a lot of power needed. Tony, perhaps you might be able to suggest how the 5 amp supply could be enhanced? On the other hand, with a BA23 being relatively easy to locate, perhaps it is not worth while even asking. I recently managed to acquire a 3rd BA123 box (with 12 slots) to be a spare in case one of the other 2 power supplies on the other BA123 boxes fails. As for modes of failure, how often should a power supply be used to be sure that keeping it out of service does not cause a failure when the power supply is used after a few years? Does anyone have any recommendations? Sincerely yours, Jerome Fine

Jerome Fine replies: Well, maybe soldering a VT103 backplane was not so bad, but I seem to remember the problems I once had with a DRV11 module. It needed to be strapped, but the only way that DEC provided to change the CSR value was with zero ohm resistors. Removing a strap just meant cutting out a resistor. But I found it impossible to add a resistor. Finally after several hours of unsuccessful attempts (and almost damaging the board), I solved the problem by removing a few male connector pins from a damaged board and soldering them into the appropriate holes where the zero ohm resistor leads would normally be placed. Since the very tiny pin was easy to manipulate and could be easily inserted into a melted solder hole, I ended up with two pins which I could them wire wrap since the pins were very similar to wire wrap posts in the first place. Why DEC had not done that to start with I don't know, but I finally did change the CSR value. And it took about TWO hours each to finally insert each pin. Needless to say, I am not a bit fan of making solder connections at this point. As far as I know, the LSI-11 CPU modules (both dual and quad) do use some of those address lines. But the M8186, M8189, M8190 and M8192 can't since they all support 22 bit addresses for memory. So the VT103 backplane from DEC with 18 bit address lines probably supports the use of the LSI-11 CPUs, but not after modification to 22 bit addresses. Since the PDP-11/73 CPUs are now readily available, I can't see anyone using an LSI-11 CPU at this point except in VERY unusual situations which require the LSI-11 CPU for a special reason - like the microcode which can be modified. I don't know of anyone who ever modified the microcode for an LSI-11 CPU. That is not to say that I will not invent new PDP-11 instructions such as an UNSIGNED multiply, 32 bit multiply and divide which will be implemented under Ersatz-11. But as the fellow in Irma La Duce said "That is another story." Not knowing about stray magnetic fields, I just put an ST412 (actually a DEC RD51) under the tube and started to run. This used a Sigma RQD11-B MFM controller (dual board with boot ROMs) with an M8186. Worked great. Made them available to Ontario Hydro as a work station. Since they were already using the VT103 with a dual RX02 floppy drive, the hard drive was a huge improvement. They ran RT-11 and having a 10 MByte hard drive rather than a 0.5 Mbyte floppy made a huge improvement. Expensive at the time, but worth while for commercial use. Yes! I did mean the 5 Volt which is limited to 16 Amps on the VT103. And that includes all of the boards, including the VT100 video card and anything else in the VT100 which uses the 5 Volt level. I thought as much. I will continue to use the BA23 and BA123 for now. Since the core 2 duo CPU runs Windows XP which runs Ersatz-11 which runs RT-11 at more than 100 times the speed of a PDP-11/93, it is not likely that I will be using a real DEC CPU much in any case. By the way, with SATA II drives, the disk I/O is probably 200 times faster than any ESDI or SCSI drive connected to a PDP-11. I probably turn on the PDP-11/83 about 2 times a year. Since I had 2 BA123 power supplies fail in the past 10 years, I wondered about having to use them or loose them. At one point, I was told by a company that I did some software programming for that their major customer required them to run the PDP-11 systems every 3 months until delivery which was not to be for 2 years. Thus the reason for my question. Sincerely yours, Jerome Fine

Jerome Fine replies: A MXV11 (or other board with a bootstrap) is needed only when a DEC controller (without a bootstrap) is used. Most (probably all) 3rd party controllers or host adapters contain bootstrap code. Note that neither the M8186 nor the M8192 (KDJ11-A) contain a bootstrap (or a serial DL port). Both the M8189 and the M8190 quad boards contain a bootstrap, although the versions available with the M8189 are often restricted to RL02 / RX02 drives. An external hard disk enclosure is not essential. I usually just use a PC power supply and a bare hard drive with the cables from the controller hanging out the back of the VT103, especially when using an ESDI hard drive which requires more power than an MFM hard drive. I suggest that you also place a fan beside any ESDI hard drive since they usually run very hot. Note that an RQDX3 (dual board from DEC WITHOUT a boot ROM) is probably quite reasonable with an M8190 and Qbus memory as far as power is concerned. An RQDX1/2 (quad board from DEC WITHOUT a boot ROM) needs 6 amps for the 5 volts and will often overload the VT103 power supply when the other boards are added to the total needed to run a minimum system. As for placing the hard drive under the CRT, while there is ample room for a 3.5" hard drive, I have managed with an ST412 5.25" hard drive - although I agree that it was a VERY tight squeeze. A third party MFM controller (with a boot ROM), M8186 / M8192, memory and DLV11-J are sufficient to run RT-11 and the VT103 power supply is sufficient to support the ST412 as well. Was that a CQD 220TM? A CQD 220T will handle only a tape drive. If you have a CQD 220TM that works, $80 is certainly a very low cost. It usually supports optical disk drives as well and may support CDROM drives. In my case, I have an Adaptec AHA 2940AU SCSI host adapter on my PC and can use a Sony SMO S-501 media to move 295 MB from the real PDP-11 to the PC running E11 under Windows 98SE. I am hoping that E11 will also be able to use the optical drive under Windows XP, but I will not know for about 6 months. Sincerely yours, Jerome Fine

Jerome Fine replies: I use a Sigma RQD11-EC quad ESDI controller which can run 4 ESDI drives. What I like best is that 3 drives are VERY easily (just ground the correct line) made WRITE PROTECTED. Not having a proper panel, I just use a 10 pin cable and alligator clips to ground the line. The Hitachi DK515 with about 600 MBytes each work well. I modified the RT-11 MSCP device driver to allow me to boot any of the 60 partitions on the 3 drives. Normally, I use 3 drives with 2 being backups and only drive 0 with 20 RT-11 partitions being modified at any time. All drives are usually WRITE PROTECTED most of the time since I normally fix bugs in the RT-11 operating system and the device drivers. Since any mistakes in my code modifications could corrupt the hard drive, having them hardware WRITE PROTECTED prevents that until I have checked out the code. After I have made the changes to the backup drives, I boot the backup drive and copy the changes to drive 0 which is now just a data drive. I have 2 command files which compare all 20 partitions on drive 0 to each of the 20 partitions on drive 1 or drive 2. That takes about 4 minutes for each pair of RT-11 partitions of 32 MBytes each or about 80 minutes in total. Under Ersatz-11 with a core 2 duo, it takes about 1.7 seconds per pair of RT-11 partitions of 32 MBytes or about 30 seconds for all 20 pair of RT-11 partitions - not even time to get a drink. I am working on enhancing the HD: device driver under Ersatz-11. It is twice as fast as the MSCP device driver. For raw throughput, if I bypass the HD: device driver code and use a user subroutine without interrupts (hardly necessary when things are this fast), making a copy of an RT-11 partition of 32 MBytes is twice as fast again. A straight copy is about 0.2 seconds for all 32 MBytes as opposed to about 240 seconds the copy an RT-11 partition on those very fast (for a real DEC PDP-11/83 system) ESDI hard drives. Sincerely yours, Jerome Fine