test-drb

test-drb@ccmp.vtda.org

101090 discussions

by johnny.billquist＠synap.se

Ok. To start with the short version. Get back when you really want more details. The deal is to fake the MK11 so that it thinks there are four 256KB cards when you have a 1MB card. The memory bus is pretty simple. You have address lines, and card select lines. Address lines are as usual. Card select lines are like chip selects, or whatever you are used to in terminology. It selects which card should respond when address and data and other control signals are on the bus. Usually only one card select line is active at a time. So you have three things to deal with: . Address lines . Card select lines . ECC Address lines are pretty simple. You grab four card select lines, hook a 4-to-2 binary multiplexor in there, and you get A18,A19 from those. This means that four adjacent cards will cause A18,A19 to be generated. Card select lines are even simpler. You just OR the four card select lines together, and output it on one of them. I seem to remember that you don't need to cut anything on the backplane, but check that to be sure. Also, you need a total of four of these special cards in order to get 4 MB working in the MK11, but all four cards will be identical. With that, the hardware side is done. Now, the one part left is a bit more tricky, but it's a hardware problem with a software solution. The MK11 (as well as the 11/750) have ECC memory. In order for the memory to not scream bloody hell when you access it, the syndrome bits must be set right. At power up, the MK11 initialize the syndrome bits for all memory in the box, but it does this in a really clever way. It runs though all addresses and do a write to them, forcing the ECC syndrome bits to be updated. *But*... It does this on all cards in the box in parallell. That is, all card select lines are active at the same time, at this one instance. The problem with that is that (obviously) not all the memory in the 1MB memory board will be reset. By designing your small adapter card the right way, you can get atleast the first 256KB ECC syndrome bits set right. The rest you'll have to do by software instead, before the memory can be used. Otherwise you'll just get parity errors if you try to access that memory. And, normal writes to memory won't work! The memory is 32 bits wide, and a normal write from a PDP-11 will only write 16 bits, so it won't cause the memory to do a blind write and just set the syndrome bits. If you read the documentation for the MK11, you'll find that it actually have a CSR as well, and in that, you can set bits to force writing the syndrome bits and ignore errors. And for the initialization that's what you need to do: set the right bits in the CSR, write to all memory needed, and then reset the CSR again. The last "funny" thing with this is that the CSR isn't easy to access. All accesses to the I/O page in an 11/70 will cause the reference to run out on the Unibus (not surprising). However, the MK11 isn't on the Unibus. :-) The trick is to realize that the Unibus map will always direct the access to the memory bus, even if the final address is in the I/O page. So, you need to setup the Unibus map to point to the I/O page, and then access the MK11 CSR through the Unibus map. After that, you're all done, and the MK11 with 1MB memory boards will be happy. I've done it in the past, and it really not any more complicated than that. Johnny

17 years, 5 months

4.3BSD Quasijarus

by bqt＠softjar.se

"Ethan Dicks" <ethan.dicks at gmail.com> wrote: > On Fri, Dec 26, 2008 at 9:35 PM, Dave McGuire <mcguire at neurotica.com> wrote: >> On Dec 26, 2008, at 9:26 PM, Ethan Dicks wrote: >>> Also, I should check the memory in it - ISTR it's limited to 5MB. >> I think 5MB is correct. And don't they use the same memory array boards as >> the PDP-11/70? > > Yes... same 1MB boards in the 11/70, 11/730, 11/725 and 11/750. Nope. The MK-11 memory box for the 11/70 (there are others) have the same memory bus as the 11/750, but the MK-11 don't support 1MB boards. Believe me, I know... 256 KB memory boards works fine in both MK-11 and 11/750 though. And if someone *really* have 1MB boards, and an MK-11, and wants to use them, contact me and I can start explaining what you need to do to actually get it to work. But it requires both serious hardware hacking and software fiddling. Johnny

17 years, 5 months

new disks, old DEC (was Re: 4.3BSD Quasijarus)

by ethan.dicks＠gmail.com

On Sat, Dec 27, 2008 at 11:39 AM, Dave McGuire <mcguire at neurotica.com> wrote: > On Dec 26, 2008, at 11:04 PM, Bob Armstrong wrote: >> >> I've also got a 11/725 that's in good shape except for a few missing >> pieces of sheet metal, but like Ethan I've no working RC25 drive. I don't know about the state of your drive, Bob, but mine is merely missing a cartridge so I can't spin up the fixed platter. For those that might not know, the RC25 is 25MB/25MB removable on one spindle. I think the original idea was that you would put VMS on the internal platter and swap out the cartridge for either backup/restore, and perhaps installs, but in practice, VMS got large enough fast enough that you really needed all 50MB for the OS and a few user dirs. You _can_ fit 5.0 on it, I've seen it, but 4.x is a better fit. >> A UNIBUS SMD controller is an option - there are some small 8" SMD disks that mist >> just fit inside the chassis in place of the RC25 - but a UNIBUS SCSI >> controller would be a better way to go, since it'd be no problem to fit a >> SCSI disk in there. Unfortunately neither SMD nor SCSI UNIBUS controllers >> are easy to come by. > > 5.25" SMD drives do exist; Seagate (and possibly others) made them. I had > a few at one point (1990?) but no more. I know someone who has some but I > doubt he'd turn loose of them. I know I've seen SMD-E drives in 5.25" form-factor, but I don't know if SMD-E drives are happy on an older SMD controller (despite using SMD drives since 1984, I really don't know lots about their limitations - I only ever worked with a couple of combinations that were known to work - I never had to match up settings and cables, etc., on random configurations as I later did plenty of times with MFM and ESDI). Given the drives I do have on hand, I would, of course, love to have a Unibus SCSI controller (or 3-4 or them, really), but they were really, really rare back in the day. Every once in a while, I entertain the idea of turning old COMBOARDs into some form of disk controller (IDE or SCSI would be the easiest), but I never get past the napkin stage of designing. What would be far more practical would be an Unibus ESDI controller, but I don't remember seeing too many of those in the past (what I did see was "lots" of SMD for Unibus and SMD or ESDI for Qbus - all popular for those that were happy enough with non-DEC controllers). It all comes down to drivers. 2BSD I know can handle Emulex and other controllers just fine. I'm not as certain about Ultrix-32 (it seemed to be heavily slanted towards a DEC system disk, at least). I recall a variety of releases of VMS drivers for SI and Emulex controllers, so it would be handy, I'd say, to identify what OS and version targets, seek out ancient driver install kits _then_ go looking for a suitable controller, but I think in practice, it'll be a case of finding a $50 card and then looking for drivers. It's this struggle that makes me start to envision what it would take to turn a COMBOARD into a low-performance disk controller. I say "low performance" because no matter how one would reasonably hack on the existing hardware, and though it has a Unibus DMA engine (the 18-bits of the Unibus are mapped into 1/4 of the memory space of the onboard 68000, so DMA cycles are as easy as a DBcc loop), it's programmed I/O >from the 68000 side, limiting the max transfer speed to about 200KB/sec. You _could_ stick a disk on it, but it really was designed as a communications controller. Since you'd have to write the drivers >from scratch anyway, one might as well start with something that's _meant_ to talk to disks. I only keep coming back to the idea since I have a stack of working boards on the shelf and I have 100% of the engineering info on them (and all the rights). Thinking of COMBOARDs, ISTR someone (more than one?) on the list found a COMBOARD in a machine they picked up some time back. I am still trying to recreate our old test/development environment with simh, but I'm lacking in a way to bootstrap a simulated 11/780 with VMS 4.x. Once I get around the issue, I have backup saveset files made from the last days of Software Results I can restore - all of the source and tools and textual docs are there, and I'd be able to "cut a tape" of the install kit for a variety of OSes and COMBOARD products. This is assuming anyone still wants to talk HASP or 3780 from a real Unibus box, of course. That's what the board did, and it did do it well. The disk-controller idea is just something I kick around from time to time. -ethan

17 years, 5 months

paging clint wolf

by emu＠e-bbes.com

Could you please contact me via PM ?

17 years, 5 months

Tandy TRS-80 Model 4

by technobug＠comcast.net

--- On Sat, 12/27/08, Michael B. Brutman <mbbrutman- cctalk at brutman.com> wrote: > I think the best idea at the moment is the conductive ink > used to fix circuit board traces. I'm going to give > that a shot - there is a trip to Rat Shack in my near > future. To repair keyboards in the past I've picked up a cheap calculator (< $1) at the dollar store, cut out the conductive pads from the keys, and pasted them in place of the hardened, non-operational pads. Works for me... CRC

17 years, 5 months

Morrow documentation

by aek＠bitsavers.org

> Anything on the "Decision I" S100 system would be nice. http://bitsavers.org/pdf/morrow/decision http://bitsavers.org/pdf/morrow/cbios

17 years, 5 months

Brian Brikon 723/4M-QT floppy drive tester documentation

by keithvz＠verizon.net

I've just purchased a Brian Instruments Brikon 723/4M-QT floppy drive tester. I've wanted one of these for quite some time, and was pretty happy to find one on ebay for $20+$23 s/h. Anyone have a manual? Anyone know what the difference would be from 723B vs 723/4M-QT ?? What's the 4M part? The QT? Any info would be helpful! Thanks Keith

17 years, 5 months

new disks, old DEC (was Re: 4.3BSD Quasijarus)

by bqt＠softjar.se

"Ethan Dicks" <ethan.dicks at gmail.com> wrote: > On Sat, Dec 27, 2008 at 1:29 PM, Bob Armstrong <bob at jfcl.com> wrote: >>> Ethan Dicks wrote: >>> I don't know about the state of your drive, Bob, but mine is merely >>> missing a cartridge so I can't spin up the fixed platter. >> I've got cartridges, but I really, really, (_really_!) doubt that it'll >> make your drive work. RC25s were notoriously unreliable even when they were >> new, and as unsealed (even the fixed platter is open to the air) drives they >> just don't age well at all. I've got two RC25 drives (well, maybe even >> three but that's another story) and none will work. I spent a couple of >> weeks working on them once, and all will now try to spin up and then fault >> with various error conditions (I've since forgotten the error codes - >> sorry). > > I've owned two 11/725s over the years. As I've posted before, I've > never had the problems with the RC25 that others report. I know they > are notorious, but _I_ never had one fail. That being said, of > course, the chances of mine working are now diminished merely because > I've said something. ;-) :-) I haven't even seen an RC25 in 20 years... But they worked back then. But then again, I was working at DEC at the time, and needed them for the work I was doing, so I guess had they failed, I would just have gotten another one. :-) >>> Every once in a while, I entertain the >>> idea of turning old COMBOARDs into some form of disk controller (IDE >>> or SCSI would be the easiest), >> Another option would be to build something that plugs into the LESI (aka >> Aztec) controller and pretends to be a disk. That'd be way cool. But I've >> never seen any documentation on the LESI interface, either electrical or the >> protocol, so I've no idea how hard that would be. As long as the interface >> remains undocumented, I'd guess "really hard". And of course the LESI >> interface wasn't very popular (it was only ever used for the TU81 and the >> RC25) so the potential market, outside of you and me, is limited :-) > > Yes... that would be an interesting way to go, but as you point out, > lack of documentation makes that an unlikely path. Don't the TK50 also use LESI? Or did I just imagine that? >> The important thing is that whatever you come up with has to be close >> enough to a standard MSCP controller so that you can boot it with the >> standard DU bootstrap and so that VMB can talk to it. Unfortunately some of >> the third party SMD controllers weren't really MSCP compatible and needed >> custom bootstraps and VMS drivers (we used to have an SI controller on a 780 >> that fell into this category) - those would be a problem unless a) you can >> also recover the software (difficult), and b) they supported a 11/730 (even >> more unlikely!). The LESI approach at least avoids this problem. > > Agreed. OS driver support is always foremost in my mind when fiddling > with 3rd party disks. We always had to wait for SI to release driver > patches for our SI9900 since a Fuji Eagle is not the same size as any > DEC disk (in our case, they would patch the geometry table in > DRDRIVER.EXE to "oversize" the RM05 entry since we didn't have any > real RM05s on the system). > > It sure would be nice to find a Unibus SCSI card that looked to the > system like a UDA50 - i.e. - true and proper MSCP emulation. I don't > know if there ever was such a product, but the VAXBI ones I saw years > later were $10,000 new. :-( There are/were several. I have a CDU-720/TM. That's CMDs Unibus version of the CQD-220. Very nice. Works about the same way as the CQD too. I also have a Viking one, but that only talks TMSCP (but I'm pretty sure they did exist for disks as well). >> Of course if you only want to run Un*x then you have more flexibility :-) > > True, and I _do_ care about Unix (2BSD for PDP-11 and Ultrix-32 for > VAX), but I also care about RT-11 and pre-6.0 VMS. > > Just thinking back to when I used to do this every day for a living, I > don't recall there ever being an ideal solution, just solutions that > fit enough criteria to be acceptable (Re: price-compatibility-capacity > matrix). If you had money, you paid for DEC disk. If you had a no > budget, you bought 3rd party and decided what features to give up (the > ability to seamlessly install the OS and upgrade at will was almost > always the first thing to go). > > Not all of the "good old days" were as good as we'd like to remember. Sure they were! But as far as disks go, until good MSCP emulating controllers came out, it was always a headache with 3rd party disks and controllers. Johnny

17 years, 5 months

Merry Newtonsday

by ard＠p850ug1.demon.co.uk

Merry Newtonsday, Christmas, Yule, Midwinter, Winter Solstice or whatever you choose to celebrate to members of the classic computer list and their families. -tony

17 years, 5 months

4.3BSD Quasijarus

by ken＠seefried.com

FWIW...we ran 4.3 (locally hacked up, of course) on our 11/750s at GaTech in the late 80s and it was really very pleasant. A lot of good research work got done on those boxes (as well as a ton of nethack). KJ

17 years, 5 months

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test-drb