- vcf-midatlantic - lists.vcfed.org

A "100%" Efficient BBS Transfer Protocol
by John Heritage 16 Oct '19

16 Oct '19

Hey folks, It always bugged me back in the day that ZModem (and even Ymodem-G) left some performance on the table. For a 14.4 kbps modem with a theoretical perfect transfer rate of 1800 characters per second (assume no data compression, flawless connection, etc) -- ZModem would give you something like 1650-1660 cps and Ymodem-G would give you up to 1730 cps under ideal conditions. Ymodem-G of course had no error recovery (though it did send CRCs to help indicate whether or not there was a problem). In the interest of trying to use 100% of "upload" bandwidth, I always wanted to write a protocol that used the back channel to send CRCs from the 'download' computer to the upload source computer. (Even on asymmetrical protocols like USRobotics standards, 450 bps 'back channel' should be enough for this..) This protocol would operate like ZModem or YModem-G where the uploader just keeps streaming, but no CRCs would be sent with the transfer. Instead, the 'sender' computer would simply pre-calculate CRCs for every 1K or so; the receiver computer would calculate after receiving that 1K, and send back to the uploader. The uploader would go back and verify that it was getting the right CRCs in the right order (you could pre-calculate these and store in RAM before the transfer starts to reduce CPU load during transfer). If no problems were encountered - you might hit that theoretical 1800 cps. If problems were encountered - you'd either pause for some period of time and then re-send the last 3-4 good sets of CRCs to alert the 'receiver' computer that the transfer had to resume from an earlier state and would start after those 3-4 CRC sets were sent. Anyway just some thoughts. Something I might try in C sometime with a couple of modems... John

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Amazing LEGO datacenter model
by Jameel Akari 16 Oct '19

16 Oct '19

I can't stop looking at this amazing thing. https://www.flickr.com/photos/78666052@N05/48569034132/in/dateposted/ "Johan Alexanderson (Jalex) Vintage Computer Room Inspired by computer rooms from the 60s and 70s." The details are just great. -- Jameel Akari

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Museum report (Saturday)
by Evan Koblentz 13 Oct '19

13 Oct '19

I went to the museum yesterday despite taking a break for a while. I needed to pick up the Lego robot stuff for my upcoming Brickfair NJ demo, and also there was an NJIT alumni tour so I figured it's good politics since I work there now. Lots of visitors from the NJIT your and then a few families throughout the rest of the day.

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Museum Report 2019-10-13
by Jeffrey Brace 13 Oct '19

13 Oct '19

A good day at the museum. It started out well with a phone call from the InfoAge front desk to make sure that someone was at VCF because there was a visitor extremely interested in visiting us. It was a 9 year old boy and his family (brother, mother, grandmother) and he wanted to see the original Mac. He had watched YouTube videos, but had never used or touched one. So I let him use MacWrite and MacPaint and Microsoft BASIC. He was high interested and had questions and stayed about an hour looking at other machines. He came from Cape May and I let his mother know about VCF East. There were about half a dozen medium interest people and another half dozen low interest visitors. So overall a good day. -- ========================================= Jeff Brace Vice President Vintage Computer Federation

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Help! Stuck bit
by Dean Notarnicola 10 Oct '19

10 Oct '19

Hey VCF peeps! I’ve got a Briel Altair replica that has a stuck bit on the front panel. I’ve verified that switch (bit) 5 lets me deposit a zero or one into any given memory address. But when I go back to examine it, it always show one regardless of the actual state of the bit. I verified that the switch is good, the led is good, and I replaced all the 74 series latches without effect. There is a 220 ohm resistor in line with it that reads 216 ohm but that should be well within spec for a 5% resistor. I could replace it with a new 2%, but I’m not sure that would fix anything. Anyone have any ideas why this bit always lights when I examine it? Thanks. Dean

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Museum Update
by corey cohen 09 Oct '19

09 Oct '19

We received a lovely donation from Nokia for some improvements in our museum to do more live demos. So Jeff and I figured we can share some of the progress. First, we bought 10 LCD televisions to hook up to the top row of displays where it's impractical to have a vintage monitor. This will allow us to have demos running on machines like our Sol-20, Vic-20, Atari 800 and Tandy CoCo. We also put up an announcement sign in the hallway outside our door. The current video display system (TV) hanging from the ceiling is really missed by many people and until we move it to a better place this will have to do. I also put my youngest son to work scraping our "sign" at the entrance to Infoage because it was peeling very badly. We painted it white with correct outdoor latex paint (I think it was spray painted before with white automobile primer or something). Later in the week we will add reflective lettering that says "Computer Museum". A bit captain obvious, but we are dealing with the public, LOL... We hope to finish this and a few other projects in the next two weeks as we have some parts on order. Here are some pics in a thread I created on our forum. http://www.vcfed.org/forum/showthread.php?71900-Updates-in-progress-at-the-… Cheers, Corey corey cohen uǝɥoɔ ʎǝɹoɔ Vintage Computer Federation, a federal 501c3 designated charity 917-747-1408 mobile corey(a)vcfed.org www.vcfed.org corey cohen uǝɥoɔ ʎǝɹoɔ Sent from my iPhone

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Re: [vcf-midatlantic] Sperry/Univac Uniscope 100 Service Manual?
by Bill Degnan 08 Oct '19

08 Oct '19

Jeff - could this be a OEM Hazeltine? Bill On Tue, Oct 1, 2019 at 12:43 PM Jeff G via vcf-midatlantic < vcf-midatlantic(a)lists.vcfed.org> wrote: > Would anyone happen to have a service manual, schematic, or ANY technical > info on a Univac Uniscope 100 terminal? I acquired one a few days ago and > its dead. I did find that the Computer History Museum has the manual and > they are seeing if they can dig it up, but if I can get a full copy or if > someone has one locally that would be better. > > If someone did have one I'd be glad to scan it if possible and make it > available. I also found some online posts where the original designer of > this posted up original drawings and talked about the thoughts behind the > design of it. > > Some pics of it on my web site as I cleaned it up here: > https://www.junknet.net/2019/09/30/sperry-uniscope-100-terminal-acquired/ > > I also acquired some Sperry/Univac "Mapper" memorabilia at the same time, > that I'll be posting up on my web site too. (Known today as BIS from > Unisys) > > Thanks, > > Bags (aka Jeff G) >

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Re: [vcf-midatlantic] VCF East 2020 -- April 24-25-26
by Bill Degnan 07 Oct '19

07 Oct '19

It should be a beautiful weekend, less likely to be rainy. Earth day weekend I think. I think I am going to do a Pentium III exhibit, if that's not too old. If you're really way back no one can identify with it. Bill On Mon, Oct 7, 2019 at 7:41 PM Tony Bogan via vcf-midatlantic < vcf-midatlantic(a)lists.vcfed.org> wrote: > > > Sorry that the rates are high. We do our best to pick a date that works > for > > most people. It's a difficult and busy time of year. Pushing it earlier > in > > April conflicts with Easter/Passover and late March is VCF PNW. Maybe > next > > year we can also take into account the marathon. > > No apologies needed jeff, there’s never going to be a good time, there’s > only the best time we could arrange given the circumstances. > Go too early and bad weather really becomes a factor, as we already know > all too well. Go too late and it’s summertime and all the problems that go > with that. > > We make the best of what we have to work with. Thank you for getting the > dates set and announced in a timely fashion, it’s a big first step towards > making this event realize it’s full potential!! > > Tony >

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VCF East 2020 -- April 24-25-26
by Evan Koblentz 07 Oct '19

07 Oct '19

Subject line says it all. Mark your calendars...

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Two months left until Festivus
by Jeffrey Brace 07 Oct '19

07 Oct '19

Sign up here: < https://docs.google.com/spreadsheets/d/1x0oSxqZXh8tmqqbUsP3KS3OywiNsEAOOmtq… > -- ========================================= Jeff Brace Vice President Vintage Computer Federation

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