@vga256 I and a friend discovered this vulnerability in 1984 or 1985, and I wrote my own little terminal program with Xmodem built in to take advantage of it. Those were the days ...

(I still have the source code and of course it was called "Leech". Back then that was a generic term for somebody who downloaded far more than they uploaded, so it was a naturally good name.)

#retrocomputing

some shitheel over at wikipedia deleted a very obscure and super interesting article about the LeechModem series of bbs protocols, that i learned about buried deep in a bbs documentary interview

what was (X/Y/Z)-Modem?

a thumbnail sketch of the original protocols: bbs file transfers using the X/Y/Z-modem file transfer protocols relied upon a similar structure. the entire file would be sent from modem to modem, one packet at a time. each packet was successfully sent (and the checksum verified), the receiver would sent an ACK (acknowledgement) that the packet was received. if the packet wasn't received, or failed the checksum, the receiver sent a NAK (negative-acknowledge) response. after 10 NAKs, the sender aborted the file transfer.

why did this matter for bbs's?
back in the day, (mostly pirate) BBSes relied on "credit" systems which limited the amount you could download before you had to do work like upload new files, or participate on the message boards. this was done to discourage "leechers" from tying up the board's phone line downloading dozens of files for hours at a time.

the BBS software only withdrew a download credit from your account when a file transfer *was successful*.....
... try to imagine how this could be exploited.

how did LeechModem work?
the creators of leechmodem realized that if the file transfer protocol sent 10 NAK responses on the very last byte of a file, the BBS would think it was a failed file transfer and abort the download. since aborted downloads didn't count against your download credits, it was like you had never downloaded the file. in reality, you already had the entire downloaded file on your computer.

it took a long time for sysops and BBS software authors to figure out how to defeat leechmodem in its many variants. one of my favourites was the second the BBS detected a user running a leechmodem protocol, it would immediately cancel the file transfer, and then withdraw *twice as much credit* from their account and send a LEECHER! message to their terminal 😆

the (now deleted) wikipedia article:
https://web.archive.org/web/20220626210439/https://en.wikipedia.org/wiki/LeechModem

#bbs #history #retroComputing

Continuing with the IBM 5181 ...

Here we have the same image, printed using overstrike. It is marginally better looking, as the dots are more completely filled in.

Overstrike takes advantage of the fact that the printer mechanism isn't perfect, so the alignment of the head is slightly different on the second pass filling in more of the paper where the first pass might have missed.

#retrocomputing

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Another image printed using the the IBM 5181 printer. This print sample was made using overstrike - printing the same thing on the line twice to improve the print quality. The dots here are slightly more robust than in the standard print mode.

Continuing with the IBM 5181 ...

I was recently reminded about overstrike printing to improve the print quality on older dot matrix printers and I added it to my code. This sample shows a blow-up of an image generated by the printer, with just a single pass (no overstrike). The next image will show the same image, but printed with overstrike.

#retrocomputing

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Blowup of print from the IBM 5181 printer. This image was printed without using overstrike. Note the blurry pixels. This is a thermal printer and this is as about as good as it gets.

Not bad for a 40+ year old low-end thermal printer. The banding is probably due to the friction-feed mechanism which is touchy and slipping.

Pictured: an IBM 5155 Portable PC, printed on an IBM 5181 printer, otherwise known as the IBM Compact Printer. It's a serial printer that uses thermal fax paper in rolls and was designed for use with the IBM PCjr. It takes data at 1200 bps.

I wrote all of the code to convert a JPG to the printer codes, except the scaling code.

#retrocomputing

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IBM PC 5155 Portable PC printed on an IBM 5181 thermal printer.

I'm taking just a quick sneak peek at the latest 86Box nightly build. I'm really looking forward to the official release v5.0.0 in a few weeks. The emulation does feel super smooth and the new 86Box VM Manager already looks beautiful.

#86Box #Emulation #RetroComputing #RetroGaming #Beta

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Running a few virtual machines using the latest 86Box nightly build.

Es überrascht mich immer wieder, was man so alles noch spät Nachts im Netz findet, was man bisher doch noch gar nicht im Blick hatte!

Im Jahre 2023 wurden sämtliche ältere Versionen von SpeedCommander komplett als Freeware veröffentlicht, inkl. der 16-Bit Versionen 1,2 und III+ für Windows 3.1. Ich war jetzt nie der größte Fan dieses Datei-Managers, aber ich beschwere mich nicht über offiziell kostenlose Retro-Software.

Kommt in die Sammlung! Nice! 😃

https://www.speedproject.de/download/jubilaeumsversionen/

#RetroComputing #FileManager #Windows #Win31 #Win311 #WfW311 #DateiManager #SpeedCommander #90er

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SpeedCommander Webseite... mit kostenlosem Zeug. :-)

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SpeedCommander, Version 1 für Windows 3.1

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SpeedCommander, Version 2 für Windows 3.1

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SpeedCommander, Version III+ für Windows 3.1

Dave Plummer stopped by and gave us one of his mesmerizers which we almost immediately attached to the side of the Honeywell 6180 Multics maintenance panel.

https://icm.museum

#vintagecomputing #retrocomputing #museum #retrogaming

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an assortment of clocks, a mesmerizer, 6120 PDP-8/e replica and a Honeywell 6180 maintenance panel.

The contenders: QuickView Pro version (dvpro), Digital Sound System 3.1 (dss) and MPXPlay 1.67 (mpx). The file: Astral Projection's "Bizarre Contact" from the album "Ten".

Enjoy these clips :D

#Retrocomputing #VacationInMyHead #Multimedia

We're in the process or lighting up our Thinking Machines CM-2 which uses a Symbolics 3670 LISP Machine as its programming front end. The CM-1 was introduced 40 years ago in 1985 and the CM-2 in 1987. While this CM-2 is a single quadrant, we plan to simulate a full CM-2 and have its iconic "deep thought" lights running. Here you can see our lamp panels displaying a clock. This work was done by Jeff Kaylin.

https://icm.museum

#vintagecomputing #retrocomputing #ai

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A thinking machines cm-2 with animated light panels

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A thinking machines cm-2 with animated light panels

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A board out of the CM-2

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The Symbolics 3670 LISP machine front end to the CM-2 running StarLISP.

We will be presenting "Recollections" at VCF West at the Computer History Museum next month. Access these systems now and experience historic operating systems and programming environments online from home!

#vintagecomputing #retrocomputing #retrogaming #operatingsystems #programming #learning

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A list of the various historical operating systems and programming environments available at SDF

This is probably stupid, but I ordered and received 200 3.5" diskette jewel cases today. I think that's probably a lifetime supply.

They will come in handy if I have to autograph more mTCP diskettes. You never know, it's happened once already!

#retrocomputing

Nobody leaves the room! #DOjS just reached 900 stars on #GitHub! 😱

https://github.com/SuperIlu/DOjS

#Javascript #MSDOS #RetroComputing #CreativeCoding #p5js #RetroDev

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screenshot from the github page showing 900 stars

The Pig and her poster have been reunited. MissPiggy ran XENIX-11 at Microsoft from 1979 to 1987. These days, misspiggy runs Version 7 UNIX from which XENIX was derived and its disks are virtualized so they can run under simulation and the real hardware.

Please support our preservation efforts at https://icm.museum

We have a partial backup of MissPiggy and one day hope to run XENIX-11 on it once again.

#community #vintagecomputing #retrocomputing #unix #microsoft #history

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A 1979 Muppets poster featuring MissPiggy hanging on the side of a decdatasystem-570 named MissPiggy

A nearly finished draft presentation of what Interim Computer Museum does and what we have done. Thank you for supporting our efforts!

For more information about us and ways to support, please visit:

https://icm.museum

#museum #seattle #pnw #vintagecomputing #retrocomputing #retrogaming #software

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a presentation booklet about interim computer museum

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a presentation booklet about interim computer museum

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a presentation booklet about interim computer museum

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a presentation booklet about interim computer museum

I pushed an update to #DOStodon (the #Mastodon client for MS-DOS):

- Updated #curl to 8.14.1
- Updated #mbedTLS to 3.6.4
- Enabled HTTP 3xx redirections

Grab it at https://github.com/SuperIlu/DOStodon

Screenshot is showing both, the DOS ( @DOSBox_Staging ) and the the win32 version (Win10).

#Javascript #RetroComputing #MSDOS #CreativeCoding #MastodonClient #FreeDOS #DJGPP #DOjS

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screenshot of two instances of a text based mastodon client both showing a timeline for the tag CatsOfMastodon

I’m a bit of a 486 architecture nerd. VL Bus, EISA, 5/3.3V, it was such an interesting time for the platform. (Was also the first PC my family had).

Just got one of those tiny integrated boards with a voltage regulator from the tail end of the era! Has PCI, a coin cell battery holder, integrated FDD controller, and so on. Going to be fun kitting it out :’).

#retrocomputing

I mean yeah, great, I get a proper BSD-4.4, 32-bit TCP/IP stack and tools. But it's taken me half a day. Getting the installation files over involved loading packet drivers and using #mTCP in a DOS session. Which works .. surprisingly well. But still .. FixPak43, reboot. MPTS, reboot. Netscape 2.02, reboot. Java 1.18, reboot. Feature Installer plug-in (no reboot). Then, finally, TCP/IP.

All this to have a machine to play with at #Blackvalley.

#OS2 #Retrocomputing #WhyAreYouReadingThis #GoDoSomethingUseful

We've expanded our open hours: Saturday - Monday 10am - 4pm.
Please visit https://icm.museum for membership and booking information.

Thank you for supporting us!

#museum #computerhistory #vintagecomputing #retrocomputing #retrogaming

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A PDP-10 and two PDP-11s in a row.

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Various disk packs and tapes

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Fresh paint on the building

As promised: PartUtil a limited partition editor that makes dual booting DOS and Win 9x without a boot manager easier.

Hide, unhide and make partitions active. Save and restore MBRs to files. And a few extra tricks that help with initial setup. Runs on any PC compatible and any version of DOS. Source code included.

(I've been using an earlier version of this for years on a PCjr. This is a complete rewrite that is finally worth sharing.)

http://www.brutman.com/PartUtil/PartUtil.html

#retrocomputing #dos

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PartUtil, a limited partition editor that makes dual booting without a boot manager easier.

Coming soon ... a utility to make swapping active partitions easier.

On my PCjr I like to switch between DOS 3.3 and DOS 5, while keeping the drive letters in the extended partition the same. To do that you have to mark the new partition active, but also hide the old partition. FDISK doesn't allow that.

Other tools exist but they are often not small machine friendly. I wrote a similar utility years ago but I lost the source code, so here it is recreated and enhanced.

#retrocomputing #dos

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A screen shot of a hard drive partition table editor. DOS 6.3 is active, while DOS 2.1 and DOS 3.3 are hidden.

Only Amiga! Rob Barlow’s Amiga 1000 on display. Happy 40th July 1985-2025!

https://icm.museum

#commodore #amiga #retrocomputing #vintagecomputing #retrogaming

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An Amiga 1000 on display at PaCommEx NW

We're just 5 people away from reaching 300 supporting members. Would you help us reach our March 2025 goal?

https://icm.museum/?join

Members can request personal logins on our 26 Remote Systems, but guest access is open to all.

Thank you for supporting our efforts!

#museum #support #fundraiser #retrocomputing #vintage #vintagecomputing #retrogaming #text

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A row of vintage systems that are accessible via TELNET

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Our PDP-10 in preservation

Nintendo Virtual Boy and Bandai コンピュータビジョン光速船 Vectrex in the ゲーセン at:

https://icm.museum

This combo is historically guaranteed to stimulate vision and audio receptors 🤣

#retrogaming #vintagecomputing #retrocomputing

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A Nintendo virtual boy and a Bandai vectrex

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Virtual boy screen

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The Bandai vectrex controller