<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>
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