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MicroPDP-11 - some questions

Okay, looking around a little further, it seems that the USDC controller is most likely SCSI - there are several references to the 1108 series being SCSI controllers scattered around Usenet, and one expired eBay auction listing it as "USDC 1108 MSCP SCSI for DEC QBUS VAX, PDP11." Ideally, since MSCP is a DEC protocol, it shouldn't require too much rejiggering to fit in my existing setup, I hope?
 
Sounds really good. The trick now will be to find the manual for that SCSI controller! The other little board by the drives was likely a SCSI/ST506 bridge. If you can't have that, no big deal (you'll likely never use it anyway.)

No rejiggering required. You just need the manual to configure the SCSI controller.

Lou
 
Yeah, I've sent out a few emails to people on Usenet who've mentioned having one, crossing my fingers that they'll reply...if not, I can just drop it in as-is, and hope for the best. I'd like it to coexist with the RQDX1 so I've still got a floppy drive, but I guess we'll see (if they conflict, I can at least try configuring the RQDX1 to resolve it.)
 
Well, I couldn't get the power supply out; it's not actually a BA-23, it's a similar form-factor design with some differences, and it was much harder to work in than I expected. Still, I got everything else, including the tape drive, which is SCSI as I thought.

I was right about the secondary board; it's an actual replacement signal-distribution board designed by "U.S. Design" - the USDC that made the SCSI board,) with its own front panel (got it, along with the faceplate.) I presume that, since the ST-506 interface comes off the signal-distribution board, the 1108 is actually just plain SCSI, which hopefully means no conflicts with my RQDX1... The whole system is a USDC product. I presume it's this "U.S. Design Corp.," given that some of the cables have a QA sticker from Maryland. I'll try getting in touch with them to see what I can find out.
 
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John,

You can have your cake and eat it too. Forget about the RQDX1. Attach an RX33 to your scsi controller with a TEAC FC-1 SCSI floppy disk adapter. You can use it to attach TEAC FD55-GFR (dec RX33). I have done this and it works fine. Actually, I even connected an RX23 also (RX23 is not a normal drive for a pdp-11 system).

I will admit though that an RX33 connected to an RQDX3 can read and write both RX33 and RX50 floppies, while I have found that RX33 connected through an FC-1 to a SCSI controller works only with RX33 floppies. I have heard, but not found a manual or tried, that a command can be sent (over SCSI) to the FC-1 that should change the data rate and sidedness and make an RX50 work.

Having two MSCP controllers in a system is interesting. Only one can be at CSR 172150, and that's the one that's going to be bootable from any usual rom bootstraps. So, if you want to use the rom bootstrap, be sure to put the device you want to boot from on the controller at 172150.

My 11/73 has an RQDX3 and KDA50 (both MSCP) in it. I usually boot from an RD31 on the RQDX3, and have the RX33s on that RQDX3 so that I can still boot from floppy. The big disk (RA72) is on the KDA50, so once booted from the small disk, I use BOOT in RT11 to then boot from the big disk.

Lou
 
Hmm, interesting. With regards to the RX-33 thing, I'm more looking for a solution that involves stuff I already have; I've been extraordinarily lucky to find what I have already, and I don't really have the play budget to go hunting down individual DEC bits 'n pieces. I'll see what I can figure out about the SCSI controller; one of my Usenet leads thinks he might have the jumper reference somewhere, so it might be possible to get them to coexist. We'll see how it goes.
 
Hmm. Upon further inspection, the replacement signal-distribution board actually has a second, smaller board on the reverse of its mounting bracket that looks to be a SCSI-to-ST-506 converter, rather than having an ST-506 interface directly. Not sure if it's possible to use it separately or not.
 
scsishugart.jpg

(Finally got a slightly less awful camera-phone! 'Course, I could really stand to just get a proper camera...)

If you look over by the left, you can see that it has the one control connector and four data connectors - twice as many as I've seen on other ST-506 controllers. The row of jumpers towards the right looks like it selects a SCSI device number from 1 to 8; not sure if additional drives get assigned sequential numbers, or what.
 
Okay, I dropped the CPU and memory in alongside my RQDX1, for a start. It powers on with no smoke, and the diagnostic lights on the M7195 MXV11-B change states, but the computer doesn't say anything on either of the MXV11-B's serial ports. I'm trying to figure this out - the replacement signal-distribution board has an extra serial port that was labeled "DIAGNOSTIC," so it may be that USDC dropped in a custom boot ROM that uses that instead. The diagnostic LEDs on the M7195 start off as octal 3, 1, 3, 7, 4, 10, 11, 13, 14, 15, 16, pause at 16 for a few seconds, and then loop back to 7, but I can't make out from the MXV11-B manual what that signifies...
 
Still no luck figuring this out. Does anybody have any idea what's going on here? I kind of suspect the OEM bootstrap theory, and I'm up for getting a couple EEPROMs and trying it with a known-good set, but the 11/73 firmware images on Bitsavers are 2x16KB, and according to the manual the MXV11 only supports up to 2x8KB...
 
commodorejohn said:
Still no luck figuring this out. Does anybody have any idea what's going on here? I kind of suspect the OEM bootstrap theory, and I'm up for getting a couple EEPROMs and trying it with a known-good set, but the 11/73 firmware images on Bitsavers are 2x16KB, and according to the manual the MXV11 only supports up to 2x8KB...
Click to expand...

Looks like you change the ROM size with jumpers on it:

prom size J50-J51 J49-J51
none
2K x 8 R R factory default
4K x 8 R I
8K x 8 I I used with MXV11-B boot roms *
J20-J21 specifies 2K user UVROMS (2716) directly addressed
J20-J19 specifies 4K or 8K ROM directly addressed.
Note J21 is a +5V post

Caution to use the MXV11-B diagnostic boot rom set the
jumpers noted with * must be selected (J-15-J17,J50-J51,
and J49-J51) as well as the boot mode option of J44-J45
 
Ya those can't be right but, I found them for you. I can't post urls so, I'll PM the address to you
 
You can get 68766 EPROMs for $8 each at http://www.unicornelectronics.com but there is also a minimum order amount, maybe $25.

You can sometimes find better deals for them on eBay. I don't see any listed currently. I have a handful myself which I got on eBay a while back.
 
Unicorn Electronics is great except for that order minimum. But I'd rather go with EEPROMs anyway as I don't have a UV eraser; I got a couple from Jameco, so hopefully I'll be able to get this figured out by next weekend.
 
Is there an 8KB EEPROM part with the correct pinout for the MXV11-B?

I wasn't aware of any suitable reprogrammable 8KB parts other than the MC68766.

Opps. I was thinking of the 24-pin sockets on the M8189 KDF11-B 11/23-Plus, where I have used 8KB MC68766 parts.

I just looked at my MXV11-B and I do have a pair of much more common 28-pin 8KB EPROM parts installed.
 
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