November 2025 - cctalk - classiccmp.org

by Christian Corti

It seems that nowadays you can't get *any* replacement for failing DEC 3639 aka 2N3639 transistors. All parts are obsolete and unobtanium, e.g. 2N3640, PN3640, MMBT3640 and so on. So, what can be used instead? The most important electrical parameter is the storage time. It needs to be *very* low, around 20-30 ns. Does it mean that a failing PDP-8 will stay a dead PDP-8 from now on? Christian

5 months, 1 week

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ST-251 MFM Hard Drive sector size question

by Mike Katz

I have an ST-251 42MB MFM hard disk drive. The documentation says the drive is 512 bytes per sector. I don't know if this is fixed (hard sectored) or not. My problem is my operating system (OS/9 Level II) wants 256 bytes per sector. The OMTI 20C-1 controller can handle that but I'm not sure if the ST-251 can. Does anyone know if the ST-251 can support 256 bytes per sector and/or how to configure it for 256 bytes per sector? Thank you, Mike

5 months, 1 week

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Ancient versions of the VAX Workstation Software (VWS)

by Hans-Ulrich Hölscher

I'm looking for ancient versions of the VAX Workstation Software (VWS) for my software collection and for my VAXstation I: - V1.0 - V1.1 - V2.0 - V3.0 V1.0 (which was called "uVMS VAXstation I graphics/windowing softwarere" back then) and V1.1 are the most wanted ones, because they are the only ones that run on MicroVMS V4.0 for the VAXstation I. Version 1.0 was shipped on two RX50s, labeled “VSI010 1/2” and “VSI010 2/2”; later versions grew bigger and from V2.0 onwards TK50s were used besides RX50 floppies as well. Best Regards, Ulli

5 months, 2 weeks

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Apple ADB Mouse

by Cameron Kelly

Hello, I am wondering if anyone here would be willing to part with their Apple ADB Mouse and is located within Canada? Best Regards, Cameron

5 months, 2 weeks

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80386 - 1985

by Murray McCullough

40 years ago this year Intel came out with the 80386 – 386 – or i386. Either seems to be correct. What this meant was a memory address of 4GB, far beyond what an average computer user would need or want, but was so much more than previously(8086, 80286); ‘true’ multi-tasking which for the average computer user didn’t mean all that much; and paging, which made virtualization possible- experimenters were over-joyed! What all this contributed to was the end of the classical/vintage-computing era. Whether this began the time of open-source OS development is debatable! Happy computing? Murray 🙂

5 months, 2 weeks

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Unix V4

by Paul Koning

https://discuss.systems/@ricci/115504720054699983 and https://www.theregister.com/2025/11/07/unix_fourth_edition_tape_rediscovere… Amazing. paul

5 months, 2 weeks

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what is it? 3850 stuff

by Donald Whittemore

Got this on eBay. 7 3850 cartridges, a piece of mag tape and some metal device in a nice box. I am trying to determine what the metal thing is. Some kind of alignment tool? For cartridge insertion in MSS unit, not track alignment? https://www.myimagecollection.com/whatisit/pic1.jpg https://www.myimagecollection.com/whatisit/pic2.jpg

5 months, 2 weeks

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OS chart

by Paul Koning

Via one of the articles about that Unix V4 tape I found this https://eylenburg.github.io/os_familytree.htm which is quite an impressive chart of operating systems old and new. A few bits are clearly incorrect or missing; for example, P/OS and TRAX are both not there. I was going to mention them to the author of that chart but I don't actually know the correct placement. (Is P/OS an RSX-11/M or M+ derivative? I should know but don't.) Neat to see RSX-15 mentioned as the ancestor of RSX-11/D. Did the earlier RSX-11 versions ever ship? I know I have seen traces of /A and/or /C... The DOS-11 and RSTS entries aren't quite right either, I can send feedback for those. Also, while VMS is reasonably listed as RSX-11/M derivative, I always thought that VAXElan was unrelated. Along the same lines, where would MicroPower/Pascal fit? paul

5 months, 2 weeks

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compute gazette article summary

by Steve Lewis

As many have heard, COMPUTE!'s GAZETTE magazine has been resurrected as of this past July 2025. And its fifth issue for November is just days away. I'm not sure if attachments are working here, but there should be a catalog summary of the article titles (for those who aren't subscribed but were curious to browse the kinds of things being covered). That same summary catalog is also archived here: https://github.com/voidstar78/GC_TOC_SUM_CAT/blob/main/CG_2025_TSC_V0_1.TXT

5 months, 3 weeks

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Looking for a bootloader

by Peter Ekstrom

I am looking for the assembler listing for a bootloader for booting from MSCP disks like RD-disks. Google has not been very helpful and my assembler knowledge is not enough for me to write one from scratch. Does anyone have one they can share? - Peter

5 months, 3 weeks

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cctalk November 2025