- vcf-midatlantic - lists.vcfed.org

HP 87XM and 82901M
by Mike Loewen 24 Jan '18

24 Jan '18

I recently picked up a 82901M dual-floppy drive to go with my HP 87XM. It took a little cleaning and lube, but it's up and running. I used ImageDisk to create a DEMO DISK and ran a few of the demo programs: http://q7.neurotica.com/Oldtech/HP/HP87XM/ Software for the 80-series machines is available in Teledisk format on the HP Computer Museum site: http://www.hpmuseum.net/collection_software.php Mike Loewen mloewen(a)cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/

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Re: [vcf-midatlantic] eBay alert -- PETs nearby
by Jeffrey Brace 23 Jan '18

23 Jan '18

> > was one, I would consider making the long trip to go fetch them and then > find homes for duplicates. Besides, I have no idea where I would put them > all... > -Alexander 'Z' Pierson > What?!? Then you are not a true hoarder. A *true* hoarder would *find* a place for them ;) If you cannot, then you will be shunned: https://www.youtube.com/watch?v=5c2etjMl3WM

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Craigslist Free Demon Attack for Commodore VIC20
by Christian Liendo 23 Jan '18

23 Jan '18

https://newjersey.craigslist.org/zip/d/free-demon-attack-for/6467678817.html It's in NJ. so I figured someone would want it

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dropping a few bits (was modem error correction)
by Jeffrey Jonas 22 Jan '18

22 Jan '18

re: John Heritage Subject: Modem Error Correction - when/what baud/bps? > My questions are -- is this a correct recollection? > and when did error correction become pretty standard ... My memory may have dropped a few bits but I remember that error correction was first in the protocol the programs implemented, not the modem. Early modems had very little signal processing. The first ones didn't even auto-dial! "smart modems" added a microcontroller mostly for autodialing. That's why xmodem, uucp and such were developed. A checksum or CRC (cyclic redundency check) was added to each block. Any error caused the entire block to be sent again. Once micro-controllers were cheap enough, error correcting was moved into the modem hardware (so long as both modems supported the same "standard"). There were several totally incompatible families of modems - async (home users, bbs) - synchronous (mainframe links) - PEP (Telebit trailblazers, favored by Unix/uucp) > i.e. An early 300 or 1200 baud "client and BBS" (or server) > would typically send the 8 bits for an ASCII byte > and an additional 2 bits -- a start and stop bit ... Once modems gained DSP (digital signal processors), the data format you "fed it" externally bore little relationship to the symbols used among the modems. External modems usually use asynchronous serial via RS232 to a UART. Internal modems are parallel, so there's no stop/start bits. Early modems were FSK: frequency shift keying. One tone for a '1' or mark, another tone for '0' or space (thus the museum's all discrete-part acoustic-coupled modem in the wood box). Faster modems use frequency and phase shifting together. See: https://en.wikipedia.org/wiki/Phase-shift_keying https://en.wikipedia.org/wiki/Constellation_diagram enough? -- Jeff Jonas

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Apple //e minor surgery
by Dean Notarnicola 22 Jan '18

22 Jan '18

While watching the NFL championships, I finally got around to fixing a non-working rescue ][e. After a power supply connector adjustment, chip reseating, keyswitch replacement, and a good cleaning, she's good as new. Not a big deal, and not my first restore, but I mention it because it occurred to me that, a few years ago, I wouldn't have had the confidence to do this. So, a huge thank you to everyone connected to VCF who have been so helpful, encouraging and generous with thier time and knowledge over the years. You know who you are, and you'll all be modest and say it's nothing, but it means a lot to me.

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parts bags, still on your grocer's shelves
by Jeffrey Jonas 22 Jan '18

22 Jan '18

I found nice zip-lock parts bags in the supermarket: box of 80: 3 1/2" x 5 7/8", double zipper on the top (short-way). They were originally "Hefty basics snack portion pack" in a yellow box. The same bags are now "Presto portion pack snack bags" in a rather generic looking box. Walmart sells teeny ziplock bags in the crafts section, next to the beads.

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OT / Looking for modems
by Martin A Flynn 22 Jan '18

22 Jan '18

I have a home project underway to set up a Citadel BBS on reasonably current hardware (HP DL360 G8 with an 8 port Digi Neo Card) Where I'm stuck is modems. Anyone have Hayes 2400 Baud Smartmodem floating around? The two specific Hays models I am interested in are 217AA and 07-00056. Before anyone asks: Dial tone is from a PBX, BBS calls will be from other analog ports on the BBS. PSTN access is blocked at the moment) Martin

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Microsoft BASIC 1.0 for the Mac 128k
by Jeffrey Brace 22 Jan '18

22 Jan '18

Now at the VCF museum. Courtesy of Corey Little who copied it. I will play with it some more when grad studies are finished. Was there a Pascal for the 128k? -- Jeff Brace

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Museum Report 2018-01-21 January 21, 2018
by Jeffrey Brace 22 Jan '18

22 Jan '18

I was at the InfoAge front desk since it was VCF's turn. Steve Anderson filled in at the VCF museum. Much thanks to him to fill in at the last minute! About 20 visitors to Infoage, 10 made their way to VCF. Maybe Steve can report on their interest level. == Jeff Brace

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Modem Error Correction - when/what baud/bps?
by John Heritage 21 Jan '18

21 Jan '18

Techie questions -- IIRC -- Part of the reason modem error correction was a big deal was because in addition to improving transfer accuracy (i.e. less loss), error correction typically reduced the number of transmitted bits per byte from 10 to 8. i.e. An early 300 or 1200 baud "client and BBS" (or server) would typically send the 8 bits for an ASCII byte* and an additional 2 bits -- a start and stop bit, or similar, but later error correcting modems (i.e. 9600bps or higher) would only need 8 bits. In practice, a 2400bps modem without error correction would be limited to ~ 240 characters per second, while the same modem with error correction would be ~ 300 characters per second raw throughput. My questions are -- is this a correct recollection? and when did error correction become pretty standard -- was it the 2400 "baud" era or was it more like 9600 bps and above? I was lucky enough to go from 1200 bps to 9600 bps in one jump, though later someone gifted me a 2400 baud modem that also had error correction, and I used that for a second machine in the house.. Thanks, John *Yes, ASCII wasn't always a standard :)

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