@gloriouscow.bsky.social
Developer of MartyPC - a cycle-accurate IBM PC/XT Emulator
https://github.com/dbalsom/martypc
and fluxfox - a PC floppy disk image library
https://github.com/dbalsom/fluxfox
Retro enthusiast and shameless computer geek
https://github.com/dbalsom/martypc
and fluxfox - a PC floppy disk image library
https://github.com/dbalsom/fluxfox
Retro enthusiast and shameless computer geek
what do all these bodges do?
they appear to address a conflict that would occur during DMA bus cycles when you had a certain peripheral installed that would do DMA transfers from the upper half of memory (the logic is gated on address line A19)
they appear to address a conflict that would occur during DMA bus cycles when you had a certain peripheral installed that would do DMA transfers from the upper half of memory (the logic is gated on address line A19)
November 27, 2025 at 11:43 PM
what do all these bodges do?
they appear to address a conflict that would occur during DMA bus cycles when you had a certain peripheral installed that would do DMA transfers from the upper half of memory (the logic is gated on address line A19)
they appear to address a conflict that would occur during DMA bus cycles when you had a certain peripheral installed that would do DMA transfers from the upper half of memory (the logic is gated on address line A19)
That means when IBM realized they had a fix to make, they had to do this:
November 27, 2025 at 11:35 PM
That means when IBM realized they had a fix to make, they had to do this:
On the original 5150 motherboards, U101 was just a spare IC spot. No traces ran to it.
November 27, 2025 at 11:35 PM
On the original 5150 motherboards, U101 was just a spare IC spot. No traces ran to it.
U100 is just a spare IC spot. No traces to connect to it. IBM just anticipated they might need to throw in some extra logic as a fix, so this was a way a chip could be added and then bodge-wired however was needed.
IBM loved their bodge wires. They were usually yellow.
IBM loved their bodge wires. They were usually yellow.
November 27, 2025 at 11:27 PM
U100 is just a spare IC spot. No traces to connect to it. IBM just anticipated they might need to throw in some extra logic as a fix, so this was a way a chip could be added and then bodge-wired however was needed.
IBM loved their bodge wires. They were usually yellow.
IBM loved their bodge wires. They were usually yellow.
We can do some cool stuff with this
here's a visualization of how the CPU address lines flow out to the address latches
#retrocomputing
here's a visualization of how the CPU address lines flow out to the address latches
#retrocomputing
November 27, 2025 at 10:01 PM
We can do some cool stuff with this
here's a visualization of how the CPU address lines flow out to the address latches
#retrocomputing
here's a visualization of how the CPU address lines flow out to the address latches
#retrocomputing
November 27, 2025 at 7:27 PM
The basic concept was patented in 1917!
November 24, 2025 at 5:10 AM
The basic concept was patented in 1917!
you sent me down a rabbit hole on this one.
apparently the way this thing works is the lever arm is like a two-axis pointer, but it corresponds directly to a tray of lettersets. The lever action plucks the selected character out of the tray and plonks it up onto the roller and somehow puts it back
apparently the way this thing works is the lever arm is like a two-axis pointer, but it corresponds directly to a tray of lettersets. The lever action plucks the selected character out of the tray and plonks it up onto the roller and somehow puts it back
November 24, 2025 at 5:03 AM
you sent me down a rabbit hole on this one.
apparently the way this thing works is the lever arm is like a two-axis pointer, but it corresponds directly to a tray of lettersets. The lever action plucks the selected character out of the tray and plonks it up onto the roller and somehow puts it back
apparently the way this thing works is the lever arm is like a two-axis pointer, but it corresponds directly to a tray of lettersets. The lever action plucks the selected character out of the tray and plonks it up onto the roller and somehow puts it back
my favorite detail about the whole affair is that at the peak of people's frustration with their drives just dying out of the blue and going "click-click-click" is that IoMega, the company that made the Zip disk, came out with a new product during all this and called it...
Clik. I shit you not.
Clik. I shit you not.
November 24, 2025 at 4:26 AM
my favorite detail about the whole affair is that at the peak of people's frustration with their drives just dying out of the blue and going "click-click-click" is that IoMega, the company that made the Zip disk, came out with a new product during all this and called it...
Clik. I shit you not.
Clik. I shit you not.
The old resource viewer i wrote still works!
November 24, 2025 at 3:13 AM
The old resource viewer i wrote still works!
Here's the pathing & occlusion mask for that scene. The black region is where you can walk. The green path would have triggered Rif's sprite to get smaller.
Notice how you can go completely around that big tree, although I don't think there was ever an occasion to do so in the game.
Notice how you can go completely around that big tree, although I don't think there was ever an occasion to do so in the game.
November 24, 2025 at 3:00 AM
Here's the pathing & occlusion mask for that scene. The black region is where you can walk. The green path would have triggered Rif's sprite to get smaller.
Notice how you can go completely around that big tree, although I don't think there was ever an occasion to do so in the game.
Notice how you can go completely around that big tree, although I don't think there was ever an occasion to do so in the game.
Here's a photo of the team that made it!
November 24, 2025 at 2:46 AM
Here's a photo of the team that made it!
And here's its corresponding collision and occlusion mask. There's no reason to draw the top part, because Rif can't walk up that high!
November 24, 2025 at 2:43 AM
And here's its corresponding collision and occlusion mask. There's no reason to draw the top part, because Rif can't walk up that high!
Here's a background from the game...
November 24, 2025 at 2:43 AM
Here's a background from the game...
I even added a quake-style console. Because why not.
November 24, 2025 at 2:43 AM
I even added a quake-style console. Because why not.
The game could use arbitrary convex polygons for hit-detection. Re-implementing that algorithm was a real pain in the butt, but very satisfying when I got it working.
November 24, 2025 at 2:43 AM
The game could use arbitrary convex polygons for hit-detection. Re-implementing that algorithm was a real pain in the butt, but very satisfying when I got it working.
I just saved your post to this disk
November 24, 2025 at 2:21 AM
I just saved your post to this disk
More MOO-related pixel art
November 15, 2025 at 7:05 PM
More MOO-related pixel art
more flux cats?
November 10, 2025 at 10:17 PM
more flux cats?
November 10, 2025 at 10:08 PM
I did work on a few angles of Scar sprites to replace the spider mastermind, he was going to have been behind it all
November 10, 2025 at 9:53 PM
I did work on a few angles of Scar sprites to replace the spider mastermind, he was going to have been behind it all
November 10, 2025 at 6:41 PM
From Infoworld, July 1983.
My guy generated SIX FEET of code. How many feet of code did you write today?
#retrocomputing
My guy generated SIX FEET of code. How many feet of code did you write today?
#retrocomputing
November 5, 2025 at 3:19 AM
From Infoworld, July 1983.
My guy generated SIX FEET of code. How many feet of code did you write today?
#retrocomputing
My guy generated SIX FEET of code. How many feet of code did you write today?
#retrocomputing
The test suite includes 941 test files (406 opcodes plus operand size and address size prefix combinations) comprising 1,758,700 individual, heuristically-generated instruction tests, all of them containing cycle exact captures of the execution of a real 386 CPU under the control of an Arduino Giga.
November 4, 2025 at 8:16 PM
The test suite includes 941 test files (406 opcodes plus operand size and address size prefix combinations) comprising 1,758,700 individual, heuristically-generated instruction tests, all of them containing cycle exact captures of the execution of a real 386 CPU under the control of an Arduino Giga.