Gregory's Server
 40 comments
in february, i reverse engineered the Game Blaster sound card, all except for the weird custom chip. https://mastodon.social/@tubetime/109841846287576462. early 6502 chips were missing the ROR instruction. this isn’t a bug, and i made a YouTube video about that. speaking of the 6502, i also repaired some SYM-1 single board computers. https://mastodon.social/@tubetime/109927905082333397 as you may know i have been working with CuriousMarc at his YouTube channel. in March, i was able to extract data off the very first style of floppy disk, the IBM Minnow disk. https://www.youtube.com/watch?v=WkzPvTQSIgM also in march, i obtained a Sun Sparcstation 1+ and managed to get it working. https://mastodon.social/@tubetime/110040949079759243 i also got an IBM PS/2 model 25 which i coaxed into functionality. it was quite a journey–i even had to 3D print a key! https://mastodon.social/@tubetime/110081169895862662 someone nerd sniped me when they revealed that the earliest IBM Thinkpad, the 700, was actually a Micro Channel PS/2 inside! naturally, i had to get one and get it working. this turned into several large projects! https://mastodon.social/@tubetime/110046783196455905 did you know that, at one point, they made vacuum tubes that were the size of transistors? they were called Nuvistors, and here’s an epic thread about them. (and yes, i cut one in half!) https://mastodon.social/@tubetime/110154698725449539 in April, my logic analyzer totally broke again, but i was able to fix it. you’ll never believe what the problem was. https://mastodon.social/@tubetime/110251165148089550 Matt Venn interviewed me in May about the MOnSter 6502. https://chaos.social/@matthewvenn/111170293439000934 i spent too much money on a Pentium 90 CPU complex for my PS/2 model 95. it wasn’t working on arrival, and it turned into quite a troubleshooting effort! https://mastodon.social/@tubetime/110443440906326663 in June i picked up and restored a weird old IBM RS/6000 workstation. this is one of the first machines with a PowerPC processor. it also uses the Micro Channel bus! https://twitter.com/TubeTimeUS/status/1671654843138854912 in July i bought an old Fluke benchtop multimeter. while repairing it, i discovered a bad custom chip. i made a PCB replacement for it! https://mastodon.social/@tubetime/110646271352858078 ever shelve a project for a long time and revisit it later? i built this Panaplex clock 4 years ago but didn’t finish it up and release the design until July. https://mastodon.social/@tubetime/110680469380657195 while working on the RS/6000, i discovered that it required a special PS/2 keyboard that implemented an extra command. i made a little box that lets you use a standard PS/2 keyboard. https://mastodon.social/@tubetime/110798263588229059 with all these workstations on my bench, i designed a video adapter to convert 13W3 connections to standard VGA. https://mastodon.social/@tubetime/110726122938943639 remember that Thinkpad 700 from earlier? i started a massive project to build a replacement solid state hard drive for it. the drives were not IDE; they were a special IBM interface called DBA-ESDI. https://mastodon.social/@tubetime/110783604330499249 did you know that some early radio transmitters were electromechanical? i didn’t either! https://mastodon.social/@tubetime/110970146022678448 at the last Electronics Flea Market (in September) i found a strange bit of electromechanical aircraft avionics. check it out! https://mastodon.social/@tubetime/111043677193721723 some old DOS utilities had a graphical mouse cursor in text mode! i’ve investigated how they did it. https://mastodon.social/@tubetime/111123817309591559 in October, i spent a bunch of time reverse engineering the power board from the IBM Thinkpad 700. it was a good excuse to switch to KiCAD 7, which allows you to overlay your layout on top of an image–perfect for reverse engineering work! https://mastodon.social/@tubetime/111298635503517686 most recently, i reverse engineered a rare Apple II sound card (a sampler) using some blurry photos AND ARTWORK ON A RECORD ALBUM COVER!! https://mastodon.social/@tubetime/111508413193886509  @tubetime It was done dynamically redefining the appearance of a group of characters. This was only possible on VGA (and some older EGA) video cards. Assuming the mouse pointer can move one pixel in any direction, and the mouse pointer occupies the room of only one character, you will need to redefine one, two, or four characters, depending on the pointer location.  @tubetime Oh, that was not that difficult. VGA could display two 256 char fonts at once. You selected thag by a single bit in the color attribute. All you need to do is to render the characters occupied by the mouse-cursor into font2 and put the mouse-cursor image on top of it. Then adjust character and attributes as needed. You could render quite a bit of bitmap graphics that way in text-mode.  @tubetime that was the next step after spark gap transmitters, IIRC.   @tubetime one of my backburner projects is a simple Arduino-based USB to PS/2 adapter, initially to do some fun stuff with older PS/2 mice - do you have any good references or other examples for PS/2 comms that you could share? I had a look at the code for this and have a pretty good idea of what's happening (great comments!) but implementing something myself still feels a bit daunting. @timixretroplays can't help you with the usb but you could look at the ps/2 code in my adapter: https://github.com/schlae/RS6KB/blob/main/RS6KB.ino  @nazokiyoubinbou no the empty socket is for the CPU (which was not installed when i got it). the other device is the cache controller @tubetime I had seen some mini tube amplifiers that used tubes around this sort of size range, but they were glass. It's insane seeing all these "nuvistors" made with metal casing. It must handle heat a lot better (though I suppose it also would take longer to heat up sufficiently?) and definitely is tougher and I would imagine would last longer? Now I'm wondering why they didn't do this from the start? Harder to keep gasses from leaking? @nazokiyoubinbou metal tubes found their way into a lot of mil-spec equipment. but yeah they still needed a seal, which was typically glass. it wasn't until later they figured out how to do it without the seal. |
at the start of the year i figured out how to boot MS-DOS on my Apple II.
https://mastodon.social/@tubetime/109679227812726996