Notices by Tube❄️Time (tubetime@mastodon.social)

The existence of Norway implies the existence of Nandway.

now streaming: IBM MCGA chip reverse engineering: https://www.twitch.tv/tubetimeus

@azonenberg @whitequark i used this approach for a JTAG/I2C adapter. for efficiency, i packed a number of transfers into a single USB packet and needed a way to disburse all the received data and response codes. the API recorded the pointers, then you'd call a "flush" function that would generate the actual transfer and handle the results, after which the data at those pointers became valid.

so i got a new battery pack for my Thinkpad 700C, and this thing is wild 🧵

separated out so they are all easier to see.

ok wow that's unexpected. there's a flex circuit that sits on top of the cells inside the battery! it connects to not one, but TWO thermistors, and it has some funny bits of metal soldered on.

i pulled the front panel off, and you can see there's a good amount of circuitry in there. but let's disassemble the whole battery pack.

doing a little game reverse engineering. this time, it is Gateway by Legend Entertainment (1992)! 🧵

the 1702A is quite old as you can see by the copyright on the die. (the 1602A is the non-windowed version of the part, which is identical except for the package)

astute viewers may note that this is a legit 🧐 3M Textool socket. it cost me $25.62, or approximately 10x what a cheap clone socket costs.

i built a 1702A EPROM programmer! this design is from https://www.mattmillman.com/projects/hveprom-project/a-compact-programmer-for-1702a-eproms/

the first EPROM devices were intended to be erased using X-rays, but ultraviolet light turned out to be a more practical method (X-rays can damage chips).

here are four EPROM cells. the critical element is a transistor (circled) that has a floating gate -- a control electrode with no external connection! modern flash memories also use floating gates, but the construction is quite different.

here's the structure. the top half of the image is the address decoder and the bottom half is the array of EPROM cells.

today i learned about the Wurth SKEDD connector family. pretty odd looking, but clever!

on Wednesday i wrote and executed my first program on the IBM 1401 computer! it's all written in machine code because i seem to do things on hard mode. it worked on the second try because the first time around i miscalculated some addresses.

anyone with an RS/6000 42T (or 41T) willing to measure the case badge on the front? i just need WxL and maybe a closeup photo. this is the only other picture i could find on the entire internet.

ever wonder how you get cell service inside large buildings? they install antennas on the roof and use air-line coaxial cables, like this one, to connect them to antennas on the inside.

nobody:
F4 Phantom attitude indicator: OFF!

first, since i always seem to do stuff the hard way, i designed a board from scratch for the 2350. i call it the Rotten Pi 2350[A] mostly because i threw it together in a huge hurry two weeks ago.