foone Profile picture
12 Jan, 14 tweets, 3 min read
my favorite thing about being sick is that it seems to turn up my workaholic tendencies to 11 while making it way harder (or even impossible) to get anything done
my brain's like "YOU NEED TO DESIGN AN ISA CARD NOW!"
and I click KiCad and then my same brain is like "what are all these buttons. you don't know how to use this. this is madness."
so my stupid idea is to have an ISA card which uses
the 74HCT688 and 74HCT245 from here to decode the address/IO pins
texelec.com/product/8-bit-…
then I'm gonna use some of these TXB0108 logic level converters to take the 5v I/O of the ISA bus down to 3.3v.
adafruit.com/product/395
and then use the IO & address writes of those to go into... a raspi zero.
The idea being SPECIFICALLY that for this one it'd be easy to build an MDA/CGA clone that uses HDMI output, by just decoding the MDA/CGA address writes (+I/O) to present video over HDMI
this being inspired somewhat by the RGBtoHDMI project:
github.com/hoglet67/RGBto…
but instead of taking the output of an MDA/CGA card and turning it into HDMI video, we just replace the entire video card with our own
anyway this whole thing is just a proof of concept, really.
"raspi on an ISA bus" is something I've been thinking about for a while, because why limit it to a relatively simple video card?
by exposing the ISA bus to the raspi zero, you could develop entire new ISA cards simply by writing new software for it. The Raspi can replace a lot of things by emulating them in software.
it could easily be a serial port, even one that goes over wifi.
speaking of which, it could be a network card
and it's got an SD card, it could be a hard drive
it's got audio out (through the HDMI), maybe it's a soundcard now?
heck with flexible enough decoding of the ISA bus it could be pretty much all of these at the same time
and the cool thing is that it'd be a relatively cheap thing to do. these chips aren't expensive, and a pi zero (-w) is 5-10$

So it'd be a relatively cheap expansion for an ISA-based computer that could function as a sort of swiss-army-knife of add-on cards.
anyway. a raspi-based MDA-HDMI device seems like a relatively simple place to start and see how plausible this idea is.
MDA is basically 2K of RAM and a couple I/O ports, it's very simple.

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More from @Foone

13 Jan
fun fact: for a brief period in the early 2000s, Microsoft tried to increase the number of users who would register their software by employing hypnosis Image
This is actually the registration card that came with this odd piece of microsoft hardware. It's a set-top box from 2001 which displays JPEGs on your TV, off floppy disks. Image
I guess the idea is that it let you use a big living room TV to look at photos, instead of a small PC CRT? Image
Read 61 tweets
13 Jan
shout out to ebay who periodically decides my search on "minisport" isn't getting enough results, so it decides I must have spelled it wrong, and corrects it to "mini sport", then suggests "men sport", and I get emails like this: Image
I DO NOT WANT TINY BASKETBALLS, EBAY
I WANT ZENITH MINISPORTS Image
anyway I went in and fixed the search to have quotes in it.
ebay will fiddle with your searches unless you quote it, but sometimes it may take months before that has a noticeable effect
Read 5 tweets
13 Jan
Here's a CPT Phoenix Jr Terminal on ebay.
And wow, it's... weird!
Check out that portrait CRT, and angled keyboard! Image
It seems they tried to make the keyboard symmetric for... reasons, but the left numpad isn't a numpad, it's just got a bunch of custom keys, like TASK and PARA and LINE/SKIP/OUT/ADJ.
I imagine that was designed for customizing for the specific terminal task in mind? Image
Real Monitors Have Curves Image
Read 28 tweets
13 Jan
fun fact: the 25th amendment has two sections which allow the vice president to take over from the current president: section 3 and section 4.

They've only been invoked three times, though one is debatable. In all three cases, it involved the president's butt.
Section 4 is the one everyone is talking about recently.
It's the one that lets the vice president take over because they've judged the president to be "unable to discharge the powers and duties of [their] office"
It has never been used, though there have been a couple cases where it was considered. Two with Reagan and two with Trump.
Read 27 tweets
12 Jan
Today's pickup: A GW-12887-1! This is a replacement for the DS-12887 chip, with a replaceable battery instead of one embedded in plastic. Image
The reason? This thread's rack-mounted PC:
Read 36 tweets
12 Jan
So the last part of the Datachecker that I haven't even done a basic overview of is this huge thing, which I've been calling "the analog box". Spoiler alert: that name is inaccurate Image
This was mounted right behind the front panel, between the two hard drives. Image
It turns out each one has a separate on/off switch. Image
Read 30 tweets

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