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From: MooseFET on 14 Jun 2010 02:58 On Jun 14, 12:49 am, Paul Keinanen <keina...(a)sci.fi> wrote: > On Sun, 13 Jun 2010 07:52:12 -0700 (PDT), MooseFET > > > > <kensm...(a)rahul.net> wrote: > >On Jun 13, 2:09 am, Paul Keinanen <keina...(a)sci.fi> wrote: > >> On Sat, 12 Jun 2010 09:56:27 -0700 (PDT), MooseFET > > >> I have never used 1200 BPI tapes, but at least the 800 BPI systems > >> were extremely picky about keeping the read/write heads perpendicular > >> to the tape motion. > > >> With multiple writing drives, you really had to keep the heads aligned > >> the same way on all drives, unless you wanted to realign the read head > >> after each tape :-) > > >> At 1600 BPI, each tape channel was individually clocked, so there was > >> not so much need to keep the R/W head aligned. > > >There were lots of odd sorts of drives in the early days: > > >There were also the drives called "incremental" drives where the tape > >was moved by a stepper. Each bit group was recorded on command. > > >There are "analog" drives that where basically audio tape recorders. > >Some of these were FM where the signal was modulated onto a carrier. > >Some used other modulations. > > >There were tapes with strange numbers of tracks like 13 and 25. > > and 42 tracks. > > These were all instrumentation recorders, not computer tapes. In a lot of cases, the recorded data was later processed by a computer. There were companies in Texas that had rooms full of tape drives and spent all of their time reading reformatting and writing tapes. > All 1/2 inch computer tapes I have ever seen were 7 or 9 track. The DEC tapes were on the order of one inch wide. The reels where all that was driven. They servoed the reel motors to make the speed right.
From: John Larkin on 14 Jun 2010 09:52 On Sun, 13 Jun 2010 23:52:25 -0700 (PDT), MooseFET <kensmith(a)rahul.net> wrote: >On Jun 14, 2:19 am, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Sun, 13 Jun 2010 09:03:27 -0700 (PDT), MooseFET >> >> >> >> <kensm...(a)rahul.net> wrote: >> >On Jun 13, 11:28 pm, John Larkin >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> On Sun, 13 Jun 2010 07:52:12 -0700 (PDT), MooseFET >> >> >> <kensm...(a)rahul.net> wrote: >> >> >On Jun 13, 2:09 am, Paul Keinanen <keina...(a)sci.fi> wrote: >> >> >> On Sat, 12 Jun 2010 09:56:27 -0700 (PDT), MooseFET >> >> >> >> <kensm...(a)rahul.net> wrote: >> >> >> >Way back in the tape drive days, seismic systems wrote their data >> >> >> >onto tape. They servoed the speed of the drive so that the ADC >> >> >> >output would be matched so that ony a very little buffering was >> >> >> >needed. For marine surveys, the length of time a ship could stay >> >> >> >at sea was set by the number of tapes the ship could carry a crew >> >> >> >of perhaps 3 people would spend all day and night changing the >> >> >> >tapes. The machine would cycle between 2 or 3 drives. >> >> >> >> I have never used 1200 BPI tapes, but at least the 800 BPI systems >> >> >> were extremely picky about keeping the read/write heads perpendicular >> >> >> to the tape motion. >> >> >> >> With multiple writing drives, you really had to keep the heads aligned >> >> >> the same way on all drives, unless you wanted to realign the read head >> >> >> after each tape :-) >> >> >> >> At 1600 BPI, each tape channel was individually clocked, so there was >> >> >> not so much need to keep the R/W head aligned. >> >> >> >There were lots of odd sorts of drives in the early days: >> >> >> >There were also the drives called "incremental" drives where the tape >> >> >was moved by a stepper. Each bit group was recorded on command. >> >> >> >There are "analog" drives that where basically audio tape recorders. >> >> >Some of these were FM where the signal was modulated onto a carrier. >> >> >Some used other modulations. >> >> >> >There were tapes with strange numbers of tracks like 13 and 25. >> >> >> DECtape was cool. Bidirectional, block-structured, fun to watch. >> >> >I still have a tape. It was used on a PDP-12. The PDP-12 was a >> >machine >> >with 2 instruction sets. I was a PDP-8 and also a machine called a >> >Link. >> >An I/O operation would flip it over to a Link Mode and back. >> >> Yeah that was weird. The 8 was a 2's complement machine, and Linc was >> sign-magnitude! > >Yes, the Link ALU was complete with the end around carry. >IIRC, the Link addressed 2K word pages instead of the 4K >"fields" of the PDP-8 part. > >The OS such as it was had exactly one error message "no". > ?0.00 DON'T DO THAT John
From: MooseFET on 14 Jun 2010 09:57 On Jun 14, 9:52 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sun, 13 Jun 2010 23:52:25 -0700 (PDT), MooseFET > > > > <kensm...(a)rahul.net> wrote: > >On Jun 14, 2:19 am, John Larkin > ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Sun, 13 Jun 2010 09:03:27 -0700 (PDT), MooseFET > > >> <kensm...(a)rahul.net> wrote: > >> >On Jun 13, 11:28 pm, John Larkin > >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> On Sun, 13 Jun 2010 07:52:12 -0700 (PDT), MooseFET > > >> >> <kensm...(a)rahul.net> wrote: > >> >> >On Jun 13, 2:09 am, Paul Keinanen <keina...(a)sci.fi> wrote: > >> >> >> On Sat, 12 Jun 2010 09:56:27 -0700 (PDT), MooseFET > > >> >> >> <kensm...(a)rahul.net> wrote: > >> >> >> >Way back in the tape drive days, seismic systems wrote their data > >> >> >> >onto tape. They servoed the speed of the drive so that the ADC > >> >> >> >output would be matched so that ony a very little buffering was > >> >> >> >needed. For marine surveys, the length of time a ship could stay > >> >> >> >at sea was set by the number of tapes the ship could carry a crew > >> >> >> >of perhaps 3 people would spend all day and night changing the > >> >> >> >tapes. The machine would cycle between 2 or 3 drives. > > >> >> >> I have never used 1200 BPI tapes, but at least the 800 BPI systems > >> >> >> were extremely picky about keeping the read/write heads perpendicular > >> >> >> to the tape motion. > > >> >> >> With multiple writing drives, you really had to keep the heads aligned > >> >> >> the same way on all drives, unless you wanted to realign the read head > >> >> >> after each tape :-) > > >> >> >> At 1600 BPI, each tape channel was individually clocked, so there was > >> >> >> not so much need to keep the R/W head aligned. > > >> >> >There were lots of odd sorts of drives in the early days: > > >> >> >There were also the drives called "incremental" drives where the tape > >> >> >was moved by a stepper. Each bit group was recorded on command. > > >> >> >There are "analog" drives that where basically audio tape recorders. > >> >> >Some of these were FM where the signal was modulated onto a carrier. > >> >> >Some used other modulations. > > >> >> >There were tapes with strange numbers of tracks like 13 and 25. > > >> >> DECtape was cool. Bidirectional, block-structured, fun to watch. > > >> >I still have a tape. It was used on a PDP-12. The PDP-12 was a > >> >machine > >> >with 2 instruction sets. I was a PDP-8 and also a machine called a > >> >Link. > >> >An I/O operation would flip it over to a Link Mode and back. > > >> Yeah that was weird. The 8 was a 2's complement machine, and Linc was > >> sign-magnitude! > > >Yes, the Link ALU was complete with the end around carry. > >IIRC, the Link addressed 2K word pages instead of the 4K > >"fields" of the PDP-8 part. > > >The OS such as it was had exactly one error message "no". > > ?0.00 DON'T DO THAT The display was a vector graphics on a scope. The word "no" would appear about mid screen. The only thing that gave a clue about the error was that the size of the word "no" seemed to vary with what the error was. The command line was just the name of the program from the tape to be run and the two arguments for it. You couldn't make a huge number of different errors.
From: John Larkin on 14 Jun 2010 11:15 On Mon, 14 Jun 2010 06:57:17 -0700 (PDT), MooseFET <kensmith(a)rahul.net> wrote: >On Jun 14, 9:52 pm, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Sun, 13 Jun 2010 23:52:25 -0700 (PDT), MooseFET >> >> >> >> <kensm...(a)rahul.net> wrote: >> >On Jun 14, 2:19 am, John Larkin >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> On Sun, 13 Jun 2010 09:03:27 -0700 (PDT), MooseFET >> >> >> <kensm...(a)rahul.net> wrote: >> >> >On Jun 13, 11:28 pm, John Larkin >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> On Sun, 13 Jun 2010 07:52:12 -0700 (PDT), MooseFET >> >> >> >> <kensm...(a)rahul.net> wrote: >> >> >> >On Jun 13, 2:09 am, Paul Keinanen <keina...(a)sci.fi> wrote: >> >> >> >> On Sat, 12 Jun 2010 09:56:27 -0700 (PDT), MooseFET >> >> >> >> >> <kensm...(a)rahul.net> wrote: >> >> >> >> >Way back in the tape drive days, seismic systems wrote their data >> >> >> >> >onto tape. They servoed the speed of the drive so that the ADC >> >> >> >> >output would be matched so that ony a very little buffering was >> >> >> >> >needed. For marine surveys, the length of time a ship could stay >> >> >> >> >at sea was set by the number of tapes the ship could carry a crew >> >> >> >> >of perhaps 3 people would spend all day and night changing the >> >> >> >> >tapes. The machine would cycle between 2 or 3 drives. >> >> >> >> >> I have never used 1200 BPI tapes, but at least the 800 BPI systems >> >> >> >> were extremely picky about keeping the read/write heads perpendicular >> >> >> >> to the tape motion. >> >> >> >> >> With multiple writing drives, you really had to keep the heads aligned >> >> >> >> the same way on all drives, unless you wanted to realign the read head >> >> >> >> after each tape :-) >> >> >> >> >> At 1600 BPI, each tape channel was individually clocked, so there was >> >> >> >> not so much need to keep the R/W head aligned. >> >> >> >> >There were lots of odd sorts of drives in the early days: >> >> >> >> >There were also the drives called "incremental" drives where the tape >> >> >> >was moved by a stepper. Each bit group was recorded on command. >> >> >> >> >There are "analog" drives that where basically audio tape recorders. >> >> >> >Some of these were FM where the signal was modulated onto a carrier. >> >> >> >Some used other modulations. >> >> >> >> >There were tapes with strange numbers of tracks like 13 and 25. >> >> >> >> DECtape was cool. Bidirectional, block-structured, fun to watch. >> >> >> >I still have a tape. It was used on a PDP-12. The PDP-12 was a >> >> >machine >> >> >with 2 instruction sets. I was a PDP-8 and also a machine called a >> >> >Link. >> >> >An I/O operation would flip it over to a Link Mode and back. >> >> >> Yeah that was weird. The 8 was a 2's complement machine, and Linc was >> >> sign-magnitude! >> >> >Yes, the Link ALU was complete with the end around carry. >> >IIRC, the Link addressed 2K word pages instead of the 4K >> >"fields" of the PDP-8 part. >> >> >The OS such as it was had exactly one error message "no". >> >> ?0.00 DON'T DO THAT > >The display was a vector graphics on a scope. The word "no" would >appear about mid screen. The only thing that gave a clue about the >error was that the size of the word "no" seemed to vary with what the >error was. The command line was just the name of the program from the >tape to be run and the two arguments for it. You couldn't make a huge >number of different errors. > > FOCAL printed an error code that was a hash of the program counter at the point of error, like ?4.71 . Every release, all of the error codes changed. John
From: MooseFET on 14 Jun 2010 14:03
On Jun 14, 8:15 am, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Mon, 14 Jun 2010 06:57:17 -0700 (PDT), MooseFET > > > > <kensm...(a)rahul.net> wrote: > >On Jun 14, 9:52 pm, John Larkin > ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Sun, 13 Jun 2010 23:52:25 -0700 (PDT), MooseFET > > >> <kensm...(a)rahul.net> wrote: > >> >On Jun 14, 2:19 am, John Larkin > >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> On Sun, 13 Jun 2010 09:03:27 -0700 (PDT), MooseFET > > >> >> <kensm...(a)rahul.net> wrote: > >> >> >On Jun 13, 11:28 pm, John Larkin > >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> On Sun, 13 Jun 2010 07:52:12 -0700 (PDT), MooseFET > > >> >> >> <kensm...(a)rahul.net> wrote: > >> >> >> >On Jun 13, 2:09 am, Paul Keinanen <keina...(a)sci.fi> wrote: > >> >> >> >> On Sat, 12 Jun 2010 09:56:27 -0700 (PDT), MooseFET > > >> >> >> >> <kensm...(a)rahul.net> wrote: > >> >> >> >> >Way back in the tape drive days, seismic systems wrote their data > >> >> >> >> >onto tape. They servoed the speed of the drive so that the ADC > >> >> >> >> >output would be matched so that ony a very little buffering was > >> >> >> >> >needed. For marine surveys, the length of time a ship could stay > >> >> >> >> >at sea was set by the number of tapes the ship could carry a crew > >> >> >> >> >of perhaps 3 people would spend all day and night changing the > >> >> >> >> >tapes. The machine would cycle between 2 or 3 drives. > > >> >> >> >> I have never used 1200 BPI tapes, but at least the 800 BPI systems > >> >> >> >> were extremely picky about keeping the read/write heads perpendicular > >> >> >> >> to the tape motion. > > >> >> >> >> With multiple writing drives, you really had to keep the heads aligned > >> >> >> >> the same way on all drives, unless you wanted to realign the read head > >> >> >> >> after each tape :-) > > >> >> >> >> At 1600 BPI, each tape channel was individually clocked, so there was > >> >> >> >> not so much need to keep the R/W head aligned. > > >> >> >> >There were lots of odd sorts of drives in the early days: > > >> >> >> >There were also the drives called "incremental" drives where the tape > >> >> >> >was moved by a stepper. Each bit group was recorded on command. > > >> >> >> >There are "analog" drives that where basically audio tape recorders. > >> >> >> >Some of these were FM where the signal was modulated onto a carrier. > >> >> >> >Some used other modulations. > > >> >> >> >There were tapes with strange numbers of tracks like 13 and 25. > > >> >> >> DECtape was cool. Bidirectional, block-structured, fun to watch. > > >> >> >I still have a tape. It was used on a PDP-12. The PDP-12 was a > >> >> >machine > >> >> >with 2 instruction sets. I was a PDP-8 and also a machine called a > >> >> >Link. > >> >> >An I/O operation would flip it over to a Link Mode and back. > > >> >> Yeah that was weird. The 8 was a 2's complement machine, and Linc was > >> >> sign-magnitude! > > >> >Yes, the Link ALU was complete with the end around carry. > >> >IIRC, the Link addressed 2K word pages instead of the 4K > >> >"fields" of the PDP-8 part. > > >> >The OS such as it was had exactly one error message "no". > > >> ?0.00 DON'T DO THAT > > >The display was a vector graphics on a scope. The word "no" would > >appear about mid screen. The only thing that gave a clue about the > >error was that the size of the word "no" seemed to vary with what the > >error was. The command line was just the name of the program from the > >tape to be run and the two arguments for it. You couldn't make a huge > >number of different errors. > > FOCAL printed an error code that was a hash of the program counter at > the point of error, like ?4.71 . Every release, all of the error > codes changed. Did it do just one error and then stop? If so, a recursive decent parser sounds like the reason. When in doubt call your self. On error, clear/reload the stack. If they cleared the stack by popping, the popped value would be the return address. > > John |