But it's just stupid enough to make me happy.

So our scancode is 0b0001_1110 or 1E.
What key is that?

MartyKey::KeyA => Some(0x1E),

It's A! So, I assume that if I wire up the light pen to the keyboard port, we can use it as an IR receiver.

The first pulse is always 1, being the start bit. The start bit establishes the beginning of a series of 9 windows to follow, called bitcells. If a pulse appears at the start of a bitcell, it is a 1. if a pulse appears in the second half of a bitcell, it is a 0.

#retrocomputing

The beeping was an intentional feature by IBM to inform you that you had a bad keyboard signal. A beep occurs if the system receives a parity or phase error.

"I hate and love you so much" is something that I feel deeply

https://www.youtube.com/watch?v=OjmqTBILs6g

I'm not sure if anyone ever did - at least I'm not aware of any 3rd party IR accessories.

it would be fun to make a tiny little emitter that could send text to a PCjr and then find the next person exhibiting one at VCF and send them messages from a few tables over.

I'm sitting about ten feet away from the peanut and the keyboard seems to work just fine. Although, this is a fresh set of batteries, and it's relatively dim in here because I live like some kind of techno-troll.

#retrocomputing

There was a lot of cool stuff the VGA/TGA could do. I mean, being able to instantly switch to rendering graphics anywhere in a 128K window was a pretty crazy cool feature when you think about it - the CGA only had a measly 16K of video memory by comparison.

Unfortunately, nobody was going to make a game that relied on that, because your game had to work on the PC if you actually liked, you know, making money.

The Tandy 1000 also has a 128K window of shared DRAM, but they did two things to make the Tandy 1000 not terrible.

First, they shuffled some stuff around and tweaked some timings and basically halved the number of wait states required. Yay!

Secondly, they made the 128K shared window configurable - the system would normally move it to the top of RAM, where you were less likely to need to run code out of it, especially important stuff like DOS. Yay!

This wasn't something your IBM PC memory expansion card needed to worry about, because the PC will refresh any extra memory your put in (set your jumpers properly!)

But it also means that code running out of a PCjr RAM expansion sidecar could, in theory, run even faster than on its big older brother. Yay, peanut!

IBM gives some handwavy math to explain how you might see 2 wait states as a result. In unlucky code sequences you could see 3-5.

This made your peanut slow

Easy peasy. We just make the system RAM also the video RAM. As the PCjr's VGA reads video memory to scan out to the display, it hits all the RAS and CAS lines and we get our DRAM refreshed! Yay!

Except our CPU can't access RAM while it is doing this! Boo!