Re: [Simh] Problem with reading tape with PDP-11 SIMH
So now that Alan has TPC working, where and how do we document all this, i.e. the symptoms, the underlying SIMH design behavior vs the expected RSX behavior that cause it to manifest itself as a problem, and the DEP TS TIME solution, in an easy-to-find way so the next person doesn't have to go through this pain ? There is an awful lot of collective wisdom from the contributors to this e-mail list, but unless someone diligently searches the mailing list archives and gets lucky, it's not easy for a user to solve their own problem, even if it's been seen several times previously. The SIMH FAQ on the trailing edge web site (in PDF) has not been updated in 3 years, and the DOC version on GitHub was last updated a little over 2 years ago, and I wonder whether a better living form of documentation like a Wiki would be a more useful solution. i.e. when a system-specific usage-related problem is discovered (and hopefully fixed), the cause, effect and solution is distilled into an appropriate new or existing Wiki page. As I read the e-mails on this list, I am in constant awe at the depth of knowledge that many contributors have - in this particular case Mark and Timothe did the heavy lifting to help Alan, but there are many others whose first-hand experience back in the day drives SIMH user problems to a solution. How do we preserve everyone's legacy of product knowledge for future generations who will use SIMH long after they are gone ? To me it's as important as preserving the knowledge of the hardware SIMH simulates. Jason -Original Message- From: Simh [mailto:simh-boun...@trailing-edge.com] On Behalf Of Alan Frisbie Sent: Thursday, 21 May 2015 8:16 PM To: m...@infocomm.com Cc: SIMH@trailing-edge.com Subject: Re: [Simh] Problem with reading tape with PDP-11 SIMH Mark, Please follow Timothe Litt's suggestion and get back to me with the minimal value of DEP TS TIME which produces reasonable results for the original TPC problem you saw. Here are the results: 5000 - TPC works fine 2500 - TPC works fine 1800 - TPC works fine 1500 - TPC works fine, RSX reported tape drive errors 1350 - TPC works fine, RSX reported tape drive errors 1200 - TPC hangs 0- TPC hangs To be safe, I think I'll use 2000 from now on when using TPC. Thanks a lot for all the help. It saved me a lot of debugging and head scratching. Alan Frisbie ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
In general, I agree.The problem is not that someone should document things, but that a specific someone has to make the time available and do it... A volunteer community doesn't automagically do things. I believe GitHub allows setting up a wiki - if someone cares to manage it. In this case I believe that the plan is to update the default delay so that TPC will work with SimH out of the box. This communication may not represent my employer's views, if any, on the matters discussed. On 22-May-15 10:43, Armistead, Jason BIS wrote: So now that Alan has TPC working, where and how do we document all this, i.e. the symptoms, the underlying SIMH design behavior vs the expected RSX behavior that cause it to manifest itself as a problem, and the DEP TS TIME solution, in an easy-to-find way so the next person doesn't have to go through this pain ? There is an awful lot of collective wisdom from the contributors to this e-mail list, but unless someone diligently searches the mailing list archives and gets lucky, it's not easy for a user to solve their own problem, even if it's been seen several times previously. The SIMH FAQ on the trailing edge web site (in PDF) has not been updated in 3 years, and the DOC version on GitHub was last updated a little over 2 years ago, and I wonder whether a better living form of documentation like a Wiki would be a more useful solution. i.e. when a system-specific usage-related problem is discovered (and hopefully fixed), the cause, effect and solution is distilled into an appropriate new or existing Wiki page. As I read the e-mails on this list, I am in constant awe at the depth of knowledge that many contributors have - in this particular case Mark and Timothe did the heavy lifting to help Alan, but there are many others whose first-hand experience back in the day drives SIMH user problems to a solution. How do we preserve everyone's legacy of product knowledge for future generations who will use SIMH long after they are gone ? To me it's as important as preserving the knowledge of the hardware SIMH simulates. Jason -Original Message- From: Simh [mailto:simh-boun...@trailing-edge.com] On Behalf Of Alan Frisbie Sent: Thursday, 21 May 2015 8:16 PM To: m...@infocomm.com Cc: SIMH@trailing-edge.com Subject: Re: [Simh] Problem with reading tape with PDP-11 SIMH Mark, Please follow Timothe Litt's suggestion and get back to me with the minimal value of DEP TS TIME which produces reasonable results for the original TPC problem you saw. Here are the results: 5000 - TPC works fine 2500 - TPC works fine 1800 - TPC works fine 1500 - TPC works fine, RSX reported tape drive errors 1350 - TPC works fine, RSX reported tape drive errors 1200 - TPC hangs 0- TPC hangs To be safe, I think I'll use 2000 from now on when using TPC. Thanks a lot for all the help. It saved me a lot of debugging and head scratching. Alan Frisbie ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh smime.p7s Description: S/MIME Cryptographic Signature ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
[Simh] Problem with reading tape with PDP-11 SIMH
Before I dig too deeply into this problem, I thought I would ask if anyone else has seen it, or has some insight. I am running a relatively recent (mid-April) version of the PDP-11 simulator on my Alphastation XP1000 with VMS v8.4. The simulated PDP-11 is a copy of the physical 11/73 system I had running RSX-11M v3.0 back in 1986. So far, all simple things work just fine. For instance, I can ATTACH a .TAP tape container file to SIMH TS0, and read it (as RSX device MS0:) OK using FLX. I can also use DMP and other utilities to read the tape. The problem comes when I try to run TPC on the RSX system to create a container file. Since I was the TPC maintainer back then, I am confident that it works correctly (at least for this purpose). What appears to happen is that the first 16 or so reads of the tape complete OK, and the data gets written to the new container file on the disk. However, nothing happens after that. If I abort TPC and dump the next record on the tape, it appears to be about 16 records in from the start. (I'll verify the exact numbers next time). From this, it looks like SIMH may not be handling the read requests after the first burst, or may not be properly giving completion interrupts to the PDP-11. Remember, TPC was written to move a tape drive as fast as possible, so it will stress any emulator. I hate to blame SIMH so quickly, particularly with so few solid facts, but this system (at least on physical hardware) worked perfectly. Does anyone have any ideas or suggestions before I start a deep dive into the code? Thanks, Alan Frisbie ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On 21-May-15 15:44, Alan Frisbie wrote: Before I dig too deeply into this problem, I thought I would ask if anyone else has seen it, or has some insight. I am running a relatively recent (mid-April) version of the PDP-11 simulator on my Alphastation XP1000 with VMS v8.4. The simulated PDP-11 is a copy of the physical 11/73 system I had running RSX-11M v3.0 back in 1986. So far, all simple things work just fine. For instance, I can ATTACH a .TAP tape container file to SIMH TS0, and read it (as RSX device MS0:) OK using FLX. I can also use DMP and other utilities to read the tape. The problem comes when I try to run TPC on the RSX system to create a container file. Since I was the TPC maintainer back then, I am confident that it works correctly (at least for this purpose). What appears to happen is that the first 16 or so reads of the tape complete OK, and the data gets written to the new container file on the disk. However, nothing happens after that. If I abort TPC and dump the next record on the tape, it appears to be about 16 records in from the start. (I'll verify the exact numbers next time). From this, it looks like SIMH may not be handling the read requests after the first burst, or may not be properly giving completion interrupts to the PDP-11. Remember, TPC was written to move a tape drive as fast as possible, so it will stress any emulator. I hate to blame SIMH so quickly, particularly with so few solid facts, but this system (at least on physical hardware) worked perfectly. Does anyone have any ideas or suggestions before I start a deep dive into the code? Thanks, Alan Frisbie ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh I don't have an answer, but as it happens I'm deep into simh tapes at the moment (for reasons that will become apparent when I dig myself out.) [I'm into the tape formats/handling, not the device emulations, but that has required some digging.] Some questions to get you started: You may be right that completion interrupts are dropped. Does this happen only on the TS11 emulation? Have you tried other drive types? Do you build the simulator with the asynchronous (threaded) tape IO? If so, do you see the failures if you don't? (I believe that only some of the drive emulations use async io; I'm not current on which do and which don't.) Does your input tape have any of the unusual cases: records marked with data errors erase gaps records written over erase gaps ? Are the record sizes fixed? If you create a tape with different record sizes, does the symptom change? Is 16 the number of buffers that TPC allocates? I have in progress (but not ready to release) a utility that dumps a .tap file will report on its structure. If a dump of your tape would help, contact me off-line. smime.p7s Description: S/MIME Cryptographic Signature ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On Thursday, May 21, 2015 at 12:45 PM, Alan Frisbie wrote: Before I dig too deeply into this problem, I thought I would ask if anyone else has seen it, or has some insight. I am running a relatively recent (mid-April) version of the PDP-11 simulator on my Alphastation XP1000 with VMS v8.4. The simulated PDP-11 is a copy of the physical 11/73 system I had running RSX-11M v3.0 back in 1986. So far, all simple things work just fine. For instance, I can ATTACH a .TAP tape container file to SIMH TS0, and read it (as RSX device MS0:) OK using FLX. I can also use DMP and other utilities to read the tape. The problem comes when I try to run TPC on the RSX system to create a container file. Since I was the TPC maintainer back then, I am confident that it works correctly (at least for this purpose). What appears to happen is that the first 16 or so reads of the tape complete OK, and the data gets written to the new container file on the disk. However, nothing happens after that. I need a little more detail here. I don’t know what the TPC program is, but from what you are saying it might be a program which reads a tape and creates a TPC format tape image. If so, I wonder why you're doing this? In any case, why doesn't matter if the simulation doesn't behave like hardware did. Can you configure a TMSCP device on the simulator and in your OS (simh device TQ) and try the same activity? If it works with TQ and doesn't with TS then your recipe is good and there probably is a simulation issue. If I abort TPC and dump the next record on the tape, it appears to be about 16 records in from the start. (I'll verify the exact numbers next time). From this, it looks like SIMH may not be handling the read requests after the first burst, or may not be properly giving completion interrupts to the PDP-11. Remember, TPC was written to move a tape drive as fast as possible, so it will stress any emulator. I hate to blame SIMH so quickly, particularly with so few solid facts, but this system (at least on physical hardware) worked perfectly. Does anyone have any ideas or suggestions before I start a deep dive into the code? Does the TPC program merely use the normal OS device driver to manipulate the device, or does it attempt to directly mess with hardware? If the OS driver is being used, then the simulator will behave differently than real hardware in one significant way. Since you are saying TPC was written to move a tape drive as fast as possible, it would suggest to me that it attempts to queue multiple I/O concurrent requests to the driver. The difference with the simulator vs the real hardware is that, in general the TPC program may never get a chance to queue more than one I/O to the device since the first operation will likely complete BEFORE control returns to the user mode program. This may stress the user mode program in ways which it never saw when real tape operations took many milliseconds (or seconds). If this is happening, some adjustments to the behavior of the TS device can potentially be made to slow it down. Try sim DEP TS TIME 5000 or change 5000 to some other large number (the default is 10). - Mark ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On 21-May-15 15:54, Alan Frisbie wrote: On 05/21/2015 12:47 PM, Mark Pizzolato - Info Comm wrote: sim set ts0 format=tpc sim show ts0 TS0 not attached, write enabled, TPC format unlimited capacity sim attach -n ts0 newrsx11s.tpc File open error sim Simh does not support writing tapes in TPC format. Darn. Write in the preferred SimH format. Convert to tpc only if necessary. tpc is supported by SImH mainly for reading tapes from other sources. Most emulators will read SimH, but you can convert with external tools if necessary. Actually, it's better to convert TPC to TAP even for reading; SImH has to create an in-memory map of where all the records are when it attaches a TPC tape. This is required for backspacing and read reverse... It's cheaper to convert the file once. smime.p7s Description: S/MIME Cryptographic Signature ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On Thursday, May 21, 2015 at 12:55 PM, Alan Frisbie wrote: On 05/21/2015 12:47 PM, Mark Pizzolato - Info Comm wrote: sim set ts0 format=tpc sim show ts0 TS0 not attached, write enabled, TPC format unlimited capacity sim attach -n ts0 newrsx11s.tpc File open error sim Simh does not support writing tapes in TPC format. Darn. Can I attach a raw SCSI tape device (TSZ07 on an Alpha/VMS system)? No. There is no RAW tape support on any platform. In theory it could be added, but it would be a project. Since you are messing with tpc format tape images within your RSX environment, why not move those image files to the VMS host over the network? Better yet, make the tape in the standard simh format and convert it on the host to TPC with the mt2tpc.c program from the simtools.zip file on simh.trailing-edge.com. I'm in the middle of updating the github repo with the latest simtools.zip from trailing-edge and now will also add the things Rialto mentioned. Please follow Timothe Litt's suggestion and get back to me with the minimal value of DEP TS TIME which produces reasonable results for the original TPC problem you saw. Thanks. - Mark ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On Thu, May 21, 2015 at 4:45 PM, Mark Pizzolato - Info Comm m...@infocomm.com wrote: Since you are messing with tpc format tape images within your RSX environment, why not move those image files to the VMS host over the network? Better yet, make the tape in the standard simh format and convert it on the host to TPC with the mt2tpc.c program from the simtools.zip file on simh.trailing-edge.com. Mark, I don't see this program. In the simtools area, I do see mtcvtv23 which purports to take *.tpc and spit out *.tap Clem ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
Mark, Please follow Timothe Litt's suggestion and get back to me with the minimal value of DEP TS TIME which produces reasonable results for the original TPC problem you saw. Here are the results: 5000 - TPC works fine 2500 - TPC works fine 1800 - TPC works fine 1500 - TPC works fine, RSX reported tape drive errors 1350 - TPC works fine, RSX reported tape drive errors 1200 - TPC hangs 0- TPC hangs To be safe, I think I'll use 2000 from now on when using TPC. Thanks a lot for all the help. It saved me a lot of debugging and head scratching. Alan Frisbie ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On 21-May-15 22:38, J. David Bryan wrote: On Thursday, May 21, 2015 at 18:04, Timothe Litt wrote: If it isn't in the repo, it might as well not exist. It's hidden at the SIMH Web site: http://simh.trailing-edge.com/ ...behind the link in the phrase, Also available is a collection of tools ;-) So the site that says: V3.9 (and bug fixes to it) is the last feature release of SimH that will be hosted at this web site. All future versions can be found in a public source repository https://github.com/simh/simh. has the most recent release of the tools... :-( The one that I only visit for the non-code items...Bob's papers, etc. Hopefully Mark will merge the tools into the repo. BTW, a quick glance shows that mtdump clears the error bit before comparing a metadata word for 0 (tape mark.) This is incorrect. A tape mark is 32-bits of zero. 0x8000 is an invalid encoding and should be reported as a format error. (It indicates a length of zero with an error, but the record length field must be non-zero.) Sigh. smime.p7s Description: S/MIME Cryptographic Signature ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On Thursday, May 21, 2015 at 18:04, Timothe Litt wrote: If it isn't in the repo, it might as well not exist. It's hidden at the SIMH Web site: http://simh.trailing-edge.com/ ...behind the link in the phrase, Also available is a collection of tools ;-) -- Dave ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On 05/21/2015 11:34 AM, Mark Pizzolato - Info Comm wrote: I need a little more detail here. I don’t know what the TPC program is, but from what you are saying it might be a program which reads a tape and creates a TPC format tape image. Yes, that is exactly it. It is the original RSX tape copy program, and I was one of the authors, and primary maintainer in the 1980s, along with Glenn Everhart. If so, I wonder why you're doing this? I wanted to see if I could use it to read a TAP image of a tape to disk (as a TPC container file), then write a new tape in TPC format. I think that a TAP-to-TPC conversion utility exists, but this idea came to mind and I wanted to try it. Can you configure a TMSCP device on the simulator and in your OS (simh device TQ) and try the same activity? Not with the SYSGEN configuration I have at the moment, but I plan to SYSGEN an RSX-11M-Plus v4.6 system soon, so I will add it. If it works with TQ and doesn't with TS then your recipe is good and there probably is a simulation issue. Good point, and I will try that. Does the TPC program merely use the normal OS device driver to manipulate the device, or does it attempt to directly mess with hardware? Ordinary RSX QIO requests to the O/S. It was designed to work with both RSX-11D (and IAS) and RSX-11M. If the OS driver is being used, then the simulator will behave differently than real hardware in one significant way. Since you are saying TPC was written to move a tape drive as fast as possible, it would suggest to me that it attempts to queue multiple I/O concurrent requests to the driver. That is exactly what TPC is doing. It fires off as many asynchronous I/Os as it has buffer space for, then enters a wait state. As each read operation completes, an AST (RSX Asynchronous System Trap) routine writes it to disk, then fires off another tape read request. It only exits the mainline wait state when the end of tape data is detected. The difference with the simulator vs the real hardware is that, in general the TPC program may never get a chance to queue more than one I/O to the device since the first operation will likely complete BEFORE control returns to the user mode program. This may stress the user mode program in ways which it never saw when real tape operations took many milliseconds (or seconds). An excellent point, which I had not considered. I will have to do some exploration in this area. If this is happening, some adjustments to the behavior of the TS device can potentially be made to slow it down. Try sim DEP TS TIME 5000 or change 5000 to some other large number (the default is 10). I will try this and let you know what happens. Thanks for the information and suggestions. Alan Frisbie ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
Re: [Simh] Problem with reading tape with PDP-11 SIMH
On 05/21/2015 12:47 PM, Mark Pizzolato - Info Comm wrote: sim set ts0 format=tpc sim show ts0 TS0 not attached, write enabled, TPC format unlimited capacity sim attach -n ts0 newrsx11s.tpc File open error sim Simh does not support writing tapes in TPC format. Darn. Can I attach a raw SCSI tape device (TSZ07 on an Alpha/VMS system)? Thanks, Alan ___ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
