[GreenKeys] Got Model 33 working from PDP-8
1oldlens1
1oldlens1 at ix.netcom.com
Sun Oct 12 03:03:14 EDT 2025
This is exactly what I learned for the first Hewlett Packard mainframe machines ksorry model number gone from memory). I first keyed in the "basic binary loader" using the toggle switches. That woke up the pinched tape reader then fed in a couple of feet of tape. Maybe that was the BBL, then the program tape I punched out on the M33. Long process. This was all -hp- basic. I had to learn all this stuff on my own, never got comfortable although I earned to write elementary programs. I think the combinations keyed in with the toggle switch were called the basic binary bootstrap. For years I had that memorized and carried the BBL tape folded up in my wallet.Sent from my GalaxyRichard Knoppow Los AngelesWB6KBL
-------- Original message --------From: Harold Hallikainen via GreenKeys <greenkeys at mailman.qth.net> Date: 10/11/25 6:47 PM (GMT-08:00) To: Eric Moore <mooreericnyc at gmail.com> Cc: Green Keys <greenkeys at mailman.qth.net> Subject: Re: [GreenKeys] Got Model 33 working from PDP-8 I agree! Congratulations! My first teaching job was assembly languageprogramming on the PDP-8. We did it all with punched tape. We keyed asmall loader into core using the front panel switches. This then loadedanother loader from high speed punched tape. We then used that loader toload either an editor or an assembler. Editing was done on the Teletype33. When done, we'd punch the source file to tape and then load theassembler into core. The source tape was then run through the assemblertwice (two pass assembler!) causing an object tape to be punched. We'dthen read that into core and debug using the front panel toggle switchesand lights. Fun stuff! I have the book we used "Introduction toProgramming" for the Digital PDP-8 seriesm fifth edition from 1975 infront of me.It's interesting (to me) to look at the architecture changes between thePDP-8 and the PDP-11. First off, the 8 stuffs the return address of asubroutine as a goto in the first address of the subroutine. The return isa branch back to the first address which then goes back to the callingcode (I don't remember if the first location actually held a goto or if itjust held the address of the return with the last instruction being anindirect jump). While this works, it disallows recursion. The 11 uses astack pointer, which I think is an amazing invention. The return addressand function parameters go on the stack. Local automatic variables go onthe stack. On return, all that is discarded. VERY CLEVER!Also, I believe the 8 had special I/O instructions. In the 11, theyrealized that a input or output instruction is really the same as a reador write instruction. So, they introduced memory mapped I/O. Thissimplified the instruction set (getting rid of special I/O instructions)and allowed all memory instructions to be used on I/O devices.I also thought the instruction set of the 11 was very clever. A load withautoincrment using the program counter read literal data in memory rightafter the instruction. The same load with autoincrement with the stackpointer did a pull from the stack. Their instruction structure ofinstruction:SourceRegister:SourceMode:DestinationRegister:DestinationModeresulted in a very rich and generalized instruction set.It's interesting to see the various architecture concepts being introducedover time.Anyway, have fun with the PDP-8!Haroldhttps://w6iwi.orgOn Sat, October 11, 2025 6:19 pm, Eric Moore wrote:> Wonderful and congrats!>>> FYI, your message was a bit garbled.>>> -Eric>>> On Sat, Oct 11, 2025, 8:09 PM Jones, Douglas W via GreenKeys <> greenkeys at mailman.qth.net> wrote:>>> <div class="elementToProof">Thursday afternoon, a student and I finally>> got the U of Iowa's PDP-8 (s/n 85) to send output to our Teletype>> Model>> 33. It's taken about a decade of work with students to get this>> far, including a near ground-up rebuild of the Teletype, reforming the>> PDP-8>> power supply capacitors, tuning the memory (incompletely, at this>> point), and replacing a large number of silicon switching diodes (plus a>> few transistors) in the PDP-8. We have yet to get the TTY keyboard>> input data path to work, but I'm betting we are only days away from>> that. Here's the program that we used, successfully:</div><div>> class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont,>> Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;>> color: rgb(0, 0, 0);"><br></div><div class="elementToProof">> style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService,>> Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0,>> 0);">06000 7200>> CLA >> >> / AC = 0</div><div class="elementToProof" style="font-family: Aptos,>> Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif;>> font-size: 12pt; color: rgb(0, 0, 0);">06001 6046 A, >> TLS / main loop top,>> send AC to TTY</div><div class="elementToProof" style="font-family:>> Aptos,>> Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif;>> font-size: 12pt; color: rgb(0, 0, 0);">06002 6041 B, >> TSF / >> >> polling loop top, skip if TTY done</div><div>> class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont,>> Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;>> color: rgb(0, 0, 0);">06003 5202 JMP >> B / polling>> loop bottom</div><div class="elementToProof" style="font-family: Aptos,>> Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica,>> sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">06004 7001 >> >> IAC / >> >> advance to next character</div><div class="elementToProof">> style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService,>> Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0,>> 0);">06005 5201 JMP A >> / main loop bottom.</div><div>> class="elementToProof"><br></div><div class="elementToProof">Not very>> exciting, just repeats sending all 256 8-bit values to the TTY over and>> over (and since the TTY ignores the top bit, each run of 256 values is>> 2>> runs of the 128 ASCII codes, including CR, LF and BEL in each run, so we>> get lots of lines of output. Since the Model 33 folds upper and>> lower case, each line ha s 2 repeats of the upper-case alphabet, but>> piles up lots of characters on the right edge of the page because the>> lines are over-long. Still, a great step in our hardware>> restoration effort.</div><div class="elementToProof"><br></div><div>> class="elementToProof">The machine was delivered to the U of Iowa in>> November or more likely December of 1965,>> so we have enough working to do some nice demonstrations for the>> machine's birthday.</div><div class="elementToProof"><br></div><div>> class="elementToProof">Work remaining? Lots:</div><div>> class="elementToProof">-- TTY input</div><div class="elementToProof">-->> Tally High-speed paper-tape reader input</div><div>> class="elementToProof">-- BRPE punch output</div><div>> class="elementToProof">-- Point-plot oscilloscope display>> output</div><div class="elementToProof">-- Analog-to-digital multiplexer>> and converter input</div><div class="elementToProof"><br></div><div>> class="elementToProof">If we can get that much working, we'll b e able>> to build some joysticks (using 1965 technology, of course) and run some>> really nice games from that era.</div><div>> class="elementToProof"><br></div><div class="elementToProof"> >> >> Doug Jones</div>>> ______________________________________________________________>> GreenKeys mailing list>> Home: http://mailman.qth.net/mailman/listinfo/greenkeys>> Help: http://mailman.qth.net/mmfaq.htm>> Post: mailto:GreenKeys at mailman.qth.net>>>>>>>>> Jordan Spencer Cunningham's GreenKeys Search Tool:>>>>>>> https://teletype.net/gksearch>>>>>>> 2002-to-present greenkeys archive:>>>>>>> http://mailman.qth.net/pipermail/greenkeys/>>>>>>> 1998-to-2001 greenkeys archive:>>>>>>> http://mailman.qth.net/archive/greenkeys/greenkeys.html>>>>>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool:>>>>>>> http://comcents.com/tty/greenkeyssearch.html>>>>>> This list hosted by: http://www.qsl.net>> Please help support this email list: http://www.qsl.net/donate.html>> Message delivered to mooreericnyc at gmail.com>>>>>-- https://w6iwi.org______________________________________________________________GreenKeys mailing listHome: http://mailman.qth.net/mailman/listinfo/greenkeysHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:GreenKeys at mailman.qth.net>>> Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch>>> 2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/>>> 1998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.htmlThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.htmlMessage delivered to 1oldlens1 at ix.netcom.com
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