September 2025 - cctalk - classiccmp.org

by Martin Eberhard

I just love the PDP11's assembly language. I needed a super-tight subroutine to print a 16-bit value as 6 octal digits. This is as tight as I could make it, 16 words (including writing to the serial port, which takes 5 words). Can you beat it? ;*** Subroutine ************************* ;Print a 16-bit value as 6 octal digits ;Calling Sequence: ; jsr PC,PROCT6 ;On Entry: ; R2 = value to print ;Trashes R1,R2 ;**************************************** PROCT6: mov #100030,R1 ;Digit loop ends when '1' lands in C ;..'30' makes it ASCII sec ;All done when this is in C again ;Extract a digit and convert it to ASCII. Check for done. 1$: rol R2 ;Shift digit out of R2 & into R1 beq 3$ ;Return when done rol r1 ;Build next octal digit bcc 1$ ;Done when c = shift pattern bit ;Write digit to the serial port 2$: tstb @#CTXSTA ;Wait for transmitter (clears C) bpl 2$ movb R1,@#CTXDAT ;Transmit now ;Next digit mov #020006,R1 ;Digit ends when "2" lands in C. ;Printing ends when "sec" bit ;..leaves R2. '6' makes ASCII br 1$ 3$: rts PC Martin E.

2 hours, 8 minutes

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Re: [List] Re: Fun with PDP11 Assembly Language

by donald donaldwhittemore.com

You want blinky lights? Try this. 😊 https://www.chilton-computing.org.uk/ca/jpgs/195_engineers_console.jpg

22 hours, 33 minutes

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Re: CTOS Ethernet EDL software

by Alexei Iliasov

The driver package (B25-PDL_CTOS_Ethernet_Packet_Driver_3.7.0) also has drivers for ACCTON 1660 and 3COM 3C509 - you need to uncomment them in JCL file. I have the Accton card installed and detected in dos (and confirmed IRQ and base address) on SG3000 platform but activating the driver always crashes CTOS to core dump. The only suspect bit “Shared memory” which appears to be boot room address and this is not installed on my card (socket missing). Wonder if anyone had success with the driver?

1 day, 9 hours

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Magellan Roadmate X11-16302

by Van Snyder

Free to good home: I re-found a Magellan Roadmate X11-16302 GPS map in my junk heap. It appears to have a dead battery, at least it appeared not to charge on USB. I don't have the AC power cube or the car's cigar-lighter power adapter. Send a PDF for a shipping label from Van Snyder 2229 Shields Street La Crescenta, CA 91214 Local pick up OK too.

1 day, 15 hours

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Repairing an Olivetti M24 PSU

by Robert Jarratt

My Olivetti M24 was humming away nicely until I switched it off. It then failed to power on again. The PSU is not outputting any voltages on any of its outputs. The technical manual is here https://bitsavers.org/pdf/olivetti/m21_m24/Olivetti_M21_M24_Theory_of_Opera…. The PSU is described from p188 with an outline schematic on p194. The full schematic is on p274. A schematic useful to anyone with the actual board in front of them has been created in the following forum post https://forum.vcfed.org/index.php?t...ower-supply-replacement.1237316/#post…, the schematic is this one: https://forum.vcfed.org/index.php?attachments/m24_psu_schematic-jpg.1252584/. I have done some verification with the scope but I have reached a point where I am not sure what signals I should expect. I have attached a dummy load on the +12V, +5V and +15V outputs to meet the specs for minimum current. I see a 20KHz square wave on the inputs to the output transformer T438 (pins 1 and 2). The manual says that the diodes on the output rectify a half wave. I assume these are the ones labelled D134 and D136. The following image shows the signal on the two diodes marked D134 on the schematic for the 12V output, measured from their anodes to 0V output. https://rjarratt.wordpress.com/wp-content/uploads/2025/08/diodes-on-12v-out… For the other two diodes, labelled D136 for the 5V output I get this: https://rjarratt.wordpress.com/wp-content/uploads/2025/08/diodes-on-5v-outp… Do these look correct? The peaks seem to be too low to even begin to produce the required output voltage. Thanks Rob

3 days

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VCFMW

by Paul Anderson

I' plan on arriving there between 1 and 2 Friday afternoon. If there is anything else you want me to bring please email me off list today. If you have any US/ foreign coins/currency I'm interested in trading or buying them. Thanks, Paul

3 days, 19 hours

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UK - Northwest Computer Museum Jumble Sale

by David Wade

Folks, The Northwest Computer Museum in Leigh, Lancashire is having a jumble sale this coming Saturday. https://www.facebook.com/events/leigh-spinners-mill/tech-jumble-sale/129448… They have said I can have a table as well so I will be bringing along some of my /junk /oops surplus bits and bobs. I will have floppy disks, floppy disk drives, disk drives, keyboards, bits of Sun SPARC station, RS232 leads, PCI cards.. .. all "as seen" , most for donations to the Museum... Dave

4 days, 2 hours

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Going to e-waste unless somebody wants them

by Van Snyder

Time to clean out my basement. These are going to e-waste unless somebody wants them: Compaq Presario SR1010NX. Don't know whether it works. HP desktop box with MB and PS, no DVD, not working. Dell power supplies for data center clusters: 4 × N750P-50. 1 × PS- 2521-1D 2 × CC8823 power supplies for network switches (don't know the manufacturer; 3Com?) 3 × Ultrium fiber-channel tape drives. and a few cartridges PowerOne switching power supply Model SPM5A2M6G1K, 1 × 48VDC @ 5A, 3 × 12VDC @ 10A, 1 × 5 VDC @ 150A. Local pick-up in La Crescenta, CA is OK.

4 days, 18 hours

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Going to e-waste unless somebody wants them

by Van Snyder

Time to clean out my basement. These are going to e-waste unless somebody wants them: Compaq Presario SR1010NX. Don't know whether it works. HP desktop box with MB and PS, no DVD, not working. Dell power supplies for data center clusters: 4 × N750P-50. 1 × PS- 2521-1D 3 × Ultrium fiber-channel tape drives. and a few cartridges PowerOne switching power supply Model SPM5A2M6G1K, 1 × 48VDC @ 5A, 3 × 12VDC @ 10A, 1 × 5 VDC @ 150A. Local pick-up in La Crescenta, CA is OK.

4 days, 19 hours

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Back to the Philips P3800

by Tony Duell

Some months back I started working on a Philips P3800 computer, there was a long discussion here about the power switch and its unusual cylinder lock. At least one person was interested enough in the lock to say they would like to see it with a view to making a key At the time I didn't want to post the lock anywhere as I could have been left with a incomplete and unrepairable machine. Other projects, some of them classic-computer related got in the way. but over the last few days I've gone back to the P3800 and have made a spindle to effectively replace this lock and allow the power switch to be knob-operated (security is not an issue in my workshop :-)). Thus I could manage without the lock if I have to. So if the offer is still open I would consider posting the lock somewhere (preferably in .uk) Obviously it's 'work on it as and when you feel like it'. There's a lot of electronics for me to work on, and I'll probably take many months to sort that out. -tony

5 days, 22 hours

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