gloriouscow

Author of:
MartyPC, a PC/XT/Jr/Tandy emulator
https://github.com/dbalsom/martypc
👉 Web demo: https://martypc.net 👈

Fluxfox, a Rust disk image library
https://github.com/dbalsom/fluxfox/

ArduinoX86, a framework for controlling Intel CPUs
https://github.com/dbalsom/arduinoX86

Blog: https://martypc.blogspot.com/
GitHub: https://github.com/dbalsom/
BlueSky: https://bsky.app/profile/gloriouscow.bsky.social

Public Key

npub1dhl6470pzgczhuy6yxgpf595l998vppl0jje2swukmwyk7qny6dq0qud8y

NIP-05 Address

gloriouscow_at_oldbytes.space@momostr.pink

Profile Code

nprofile1qqsxmla2l8s3yvpt7zdzryq56z60jjnkqslhefv4g8wtdhzt0qfjdxspz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0ds5jv97n

Publishing to

relay.damus.io

nos.lol

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npub1dhl6470pzgczhuy6yxgpf595l998vppl0jje2swukmwyk7qny6dq0qud8y

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Last Notes

2026-07-19 21:27:24 UTC

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You can try removing the power supply and powering it up on its own, but don't take nothing happening as a sure sign the PSU is dead. Some of them required an active load to power up.
The power supply, even if its fine, may also not be fine, depending on how much you like Rifa smoke.

2026-07-19 21:09:50 UTC

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If you detect a short, you just need to go hunting. Sometimes they do not fail in a visibly 'sploded way.
The orange dipped caps are your likely suspects here.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/948/686/285/889/247/original/d750c3e08839c74e.png

2026-07-19 21:02:19 UTC

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Thank you for saving what you could.
One common culprit on systems of this vintage are tantalum capacitors going kerpop, which may have occurred the last time the unit was powered on, or when you did so.
The first thing to do would be to test the voltage rails from the power supply. Tantalums tend to fail short. In this scenario the power supply is usually smart enough to not power on.
If you're interested in reviving this machine, I would make a troubleshooting thread on the VCF forums.
https://forum.vcfed.org/index.php
There are many knowledgeable folks who can walk you through troubleshooting steps and repairs.

2026-05-25 14:13:59 UTC

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A fun little aside - single-step circuits for the 8080/Z80 were easy to build, you just need a handful of logic gates and a debounced switch.
Here's a example from "Build your own Z80 Computer" by Steve Ciarcia.
Pressing the button releases the WAIT signal long enough for the CPU to proceed with another instruction, whereupon it is told to WAIT again. This is independent of clock, so is a convenient way to provide a NMOS CPU its minimum clock while still being able to study it in human time scales.
Instead of WAIT, the 8080 has READY as Intel was wont to do, but it is the same principle.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/635/618/915/535/817/original/9daf42b1b58c69f5.png

2026-05-25 13:42:31 UTC

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I've got the ROM and RAM mounted in the address space. When the CPU starts, it zooms off doing something, but then gets stuck at a specific address. Maybe it's halting?
The next step is to add a single-step functionality - that will let me walk through the Space Invaders code listing one instruction at a time and make sure the CPU is actually working properly.
The DE-10 Nano has little user push buttons. Originally I was going to use those for insert coin and player 1 start, but we can multiplex their meaning based on how the user switches are set.

2026-05-25 13:34:55 UTC

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Beneath the playfield we have some debug values. PC (not hooked up yet)
A=Address bus
D= Data bus
AM is "addres mask" - i just OR all seen addresses together. That just lets me see if I missed an address line - all 16 seem to be connected
ST is the bus status byte, then we have the values for DBIN, WR and INTE.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/635/458/821/236/573/original/eb875f06709e5e5d.png

2026-05-25 00:48:44 UTC

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A colorful mess.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/632/458/203/227/203/original/128ea59c1a41fca4.jpg

2026-05-25 00:11:03 UTC

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i don't know i don't have a lot of chips just falling out of regular sockets willy nilly

2026-05-24 23:54:16 UTC

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Okay this might be a hot take and maybe it's just a skill issue but I freakin hate sockets with round holes. I don't know what the point is besides to ensure you bend a pin trying to insert your chip.

2026-05-24 23:38:26 UTC

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So just a few more things to do - we need to read the status byte during SYNC, we need to dispatch reads/writes to memory or IO as appropriate, and we need to implement an interrupt that fires off every 16,666 cycles

2026-05-24 23:17:06 UTC

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I've hooked the RESET pin up to one of the DE10's user switches so I can flip the switch to hold the CPU in reset and watch A0 stop, then flip the switch back and watch it start running again. Sweet.

2026-05-24 23:15:12 UTC

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A NOP takes 4 clock cycles, so a 2MHz 8080 will execute NOPs at 500kHz. Half of those will be at odd addresses, so we should see A0 toggle at 250kHz if the 8080 is now running.
... well, would you look at that.
It's times like this I freaking love being a huge nerd.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/632/089/663/124/814/original/aa185a4bedce7a88.png

2026-05-24 22:27:48 UTC

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All we really have to do is feed it all 0's on the data bus, because 0x00 is the NOP opcode on an 8080. It will happily do that until the heat death of the universe, so we should then see the address pins counting.

2026-05-24 22:25:17 UTC

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I think the clocks look okay now
I'm just gonna send it. Let's plug the 8080 in and see if it starts incrementing its address lines. Or whatever an 8080 does when it reads garbage
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/893/539/613/944/original/194befe87a0ef9c6.png

2026-05-24 21:06:35 UTC

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So this is my little setup. It's kinda messy. But we have our display controller, the de10-nano, the retroshield 3v teensy board, and the retroshield 8080 board. I just need to jumper gpio1 over to the teensy headers.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/583/492/516/205/original/5f929d334de6d7c6.jpg

2026-05-24 20:01:21 UTC

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I'm really going to have to check everything out under the scope once this is all hooked up.

2026-05-24 20:00:24 UTC

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This board inverts the clock lines. I thought that was odd, but then I noticed this.
Oh right, a 9V clock. Everybody knows you need a 9V clock. Silly me.
Rather than do any boosting, I suppose this code generates an inverted clock, which passes through an open-collector inverter with its outputs pulled up to 12V.
There are solder pads you can bridge if... like the driver is struggling to pull down the output clock line you can gang up three drivers?
I don't know enough to call this sketchy but I think it might be sketchy.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/312/621/772/564/original/2bbded49114b7e1c.png
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/321/755/521/152/original/d082a26a47d51276.png

2026-05-24 19:23:52 UTC

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Then we have these thingies.
This is the primary reason I never tried to make a 8080 PCB for my Arduino stuff. Because if it ain't TTL I don't know what I'm doing.
Looks like this thing is a DC-DC converter that takes 5v and outputs 15V.
How does a DC-DC converter boost voltage? Excellent question. Go ask someone who actually knows.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/174/337/754/541/original/bb4cf282ae2fdaa4.png

2026-05-24 19:19:27 UTC

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What's on this thing? First we have four 74HC245's. These are octal bus transceivers. Not sure what we need those for if we're raw-dogging the CPU but they can't really hurt to have.
The schematic shows that two of them buffer the address lines, one buffers the data bus, and the other buffers some miscellaneous signals like reset, intr and sync. Oh, and a LED. We're gonna blink the shit out of that.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/155/653/112/598/original/9219920e4d9c4cb9.png
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/161/409/689/956/original/be2002aba88d5373.png

2026-05-24 19:12:53 UTC

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Woot! I found it. It was in a box marked "my PCBs" which although technically true in the sense of ownership I dont think that's what I meant when I wrote that on there.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/137/566/704/781/original/04bff2876f9118f2.jpg

2026-05-24 19:03:23 UTC

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I'm trying to remember why I bought 16 CGA cards. They're everywhere.
Imagine you were looking for something and you had to lift up a CGA card to search each spot

2026-05-24 18:44:10 UTC

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It was probably time
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/631/026/337/873/953/original/739c698d033e7ca5.jpg

2026-05-24 18:21:38 UTC

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Well this is going to be a much shorter thread if I can't actually find where I put the 8080.
I wonder what being organized is like.
I swore I saw it a week ago. You know how you see something but somehow fail to remember the context of its position? I thought it was on my workbench. It is not.

2026-05-24 18:04:07 UTC

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What say ye, little jumper wire found on my carpet beneath the desk?
Your bends whisper of past projects. What did you help me do?
I thank you. I shall try to take you on a new adventure.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/630/865/623/208/055/original/db6e5dd934a85507.jpg

2026-05-24 17:34:51 UTC

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Ready to go! Now where did I put the 8080 board...
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/630/753/819/856/565/original/b297027007d58c3a.jpg

2026-05-24 17:14:02 UTC

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LED works. That's good. I always wire these things up backwards.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/630/671/063/711/898/original/eafa09344790c5f4.jpg

2026-05-24 17:00:12 UTC

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Let's assemble our retroshield
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/630/616/246/491/388/original/dff19e634c9d4da4.jpg

2026-05-24 00:24:36 UTC

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Nobody's actually tried it yet to my knowledge. I thought you didn't want to mess with HF!

2026-05-23 15:50:26 UTC

I'm incredibly pleased to announce that **the microcode for the Intel 80386 has been decoded**.
It was an group effort by a bunch of talented people to extract and correct the physical bits, but the major work of decoding them was done by reenigne - you may know him from such incredible PC demos as 8088 MPH and Area 5150, as well as being the person who decoded the 8088 microcode previously.
Please, check out his writeup.
https://www.reenigne.org/blog/80386-microcode-disassembled/
#retrocomputing #vintagecomputing #microcode #reverseengineering

2026-05-22 21:40:07 UTC

This weekend, I think I will try to get the DE-10 Nano controlling an 8080 CPU
I'd like to generate an emulator test suite for the 8080. I haven't previously because it's a chip that requires weird voltages and has a minimum clock of around ~1MHz.
#retrocomputing

2026-05-14 02:08:41 UTC

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you wouldn't rotate your DOS
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/570/484/045/093/932/original/e7e02a6aaf97984b.mp4

2026-05-14 01:18:21 UTC

What's your favorite version of DOS? Mine's WigglyDOS.
#retrocomputing #glyphblaster
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/570/285/037/970/659/original/32ce582ea2a476d1.mp4

2026-04-29 00:49:19 UTC

This is the McPen, a light pen by Madison Computer of Madison, WI.
Little known fact, the third largest export of the state of Wisconsin behind cheese and beer is light pens.
#nottrue #retrocomputing #lightpen
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/485/237/770/463/112/original/97c2d3ef5ced7a8e.png

2026-04-26 22:55:34 UTC

I think i broke ebay.com by buying every light pen

2026-04-25 16:43:26 UTC

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actually that's just a offhand joke, my high school guidance counsellor was a very nice lady. she gave me some really good advice once, she said, i'm paraphrasing heavily here:
you're feeling a lot of stress over your grades and your performance but let me tell you a secret - you can go to community college, and transfer out to a four year school after, and do just fine. you can live a good life without living up to other people's expectations. after you have your associates degree, nobody will care about your high school GPA ever again.
and she was 100% correct.

2026-04-25 16:39:01 UTC

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to think my high school guidance counsellor never thought i'd amount to anything

2026-04-25 16:37:38 UTC

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i'm probably topping the global leaderboard for "number of hand-made light pen adapters created"

2026-04-25 16:33:40 UTC

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First I need to make a light pen adapter. My phono boxes are delayed until Monday but I don't feel like waiting - I still have more cat6 keystone jacks to waste.
I picked up some double row Dupont connectors that should work for the PCjr end.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/466/304/925/363/614/original/8acbf29be6bd654c.jpg

2026-04-25 16:22:00 UTC

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you know what the PCjr wikipedia article needs? it needs an expanded light pen section, is what it needs.
With a photo of using a light pen with the PCjr's built in light pen diagnostic. It is the only machine I am aware of that has one!

2026-04-25 16:10:29 UTC

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I went ahead and replaced the logo that was being used on Wikipedia with it.
It was using full tilt 255 Blue and 255 Green, which is not the actual colors.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/466/214/856/140/377/original/7c7c012f4361593e.png

2026-04-25 16:04:27 UTC

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Well here it is.
https://commons.wikimedia.org/wiki/File:IBM_PCjr_Compact_Logo.svg

2026-04-25 15:41:41 UTC

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Done, nice clean SVG!
Wikipedia currently has someone's SVG conversion, but its missing the gray stripes, which I think are an iconic part of the logo.
..Do I just be a dick and replace it?
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/466/099/107/082/804/original/64c27ec289eec760.png

2026-04-25 13:42:16 UTC

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Vectorizing this. I could auto-trace it and call it a day, but I'm going to recreate it from geometric clipping masks.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/465/631/586/247/302/original/abd7714dd7ddc396.png

2026-04-25 12:56:25 UTC

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Have a crispy, 4800DPI scan of the IBM PCjr logo.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/465/455/252/750/989/original/17bfdeda0e9bc034.jpg

2026-04-25 12:47:48 UTC

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I actually need this cable, so i'll be opening it. It feels like a bit of a shame, but I'll preserve the box of course. The sheer glut of new stuff from Computer Reset basically tanked the value of any of this stuff. Any PCjr collector who wants one can have one.
Once you've opened shrinkwrap, it's best to just remove the whole thing, as the uneven stress as the shinkwrap continues to tighten can crush the box over time - although if an item is exquisitely rare and you have a mind to resell it, you may decide to let that be the next owner's problem.

2026-04-25 12:44:01 UTC

This box is 42 years old. It's eerie to look at. It looks like I plucked it off a shelf at Microcenter yesterday.
This is almost certainly from Computer Reset - a large warehouse full of old computers and new in box parts that was discovered around 2020 when the owner passed away. Among the items were hundreds of PCjr accessories, never opened.
#retrocomputing
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/465/396/209/506/750/original/2e6a24ed0c293173.png

2026-04-23 00:52:25 UTC

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this is not usually the #tandy that i boost but we're doin it

2026-04-23 00:51:41 UTC

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Ronald McTrafficsignal

2026-04-19 01:39:00 UTC

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Oh wait my bad we do need that, put that back.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/813/990/265/220/original/17b6269af4e0b084.mp4

2026-04-19 01:37:03 UTC

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The first thing a new PCjr owner is going to want to do is remove the frungus modulator. You don't need this, it was only added for compliance with French law
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/802/352/497/948/original/268be53c8926c196.mp4

2026-04-19 01:31:08 UTC

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The most famous orifices on the PCjr though have to be the cartridge slots. They're a pair of dust magnets located directly under the floppy drive.
Inserting a cartridge into one of these will immediately reboot the system without confirmation. Be sure to do that while Daddy is working on a spreadsheet.
#retrocomputing
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/780/120/010/631/original/904e232258870559.jpg

2026-04-19 01:26:29 UTC

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The D port is where you can connect a display. You can use a special cable to attach a normal CGA monitor. You can purchase such a cable for $20 from someone who got it from Computer Reset for $3
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/764/179/996/627/original/7dca3046844d3520.jpg

2026-04-19 01:22:48 UTC

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A strange property of the gaping M port is that no light can escape it. This is normal.
The M port was for a modem but this was a stupid move on Ibm's part because the Internet hadn't been invented yet.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/749/826/160/902/original/81ca2e217381388e.jpg

2026-04-19 01:19:04 UTC

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The most important port on the IBM PCjr is the LP port, which is for the light pen.
From left to right, we have the joystick ports, J J, after which JJ Abrams was named.
Nobody knows what the L port is for. If you hook a speaker to it, sometimes you hear voices in forgotten languages.
The K port is for the keyboard.
The T port is where you connect a better computer, your Tandy 1000
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/705/344/722/148/original/3f4ba8fb74d3ea58.jpg

2026-04-19 01:10:34 UTC

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The PCjr has lots of ports. But not really. They have two very large ports and plastic spacers.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/702/296/074/679/original/b67356b3d53f7a07.jpg

2026-04-19 01:04:19 UTC

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Look right in here. Right up in this connector that can make your terrible wireless keyboard a terrible wired keyboard
#retrocomputing
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/674/626/507/565/original/ece2e02dfed12fa4.jpg

2026-04-19 01:02:21 UTC

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Here are the two IR Leds and the jack for connecting a keyboard cable. Let us look closer
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/669/046/450/316/original/abaafe31946f3160.jpg

2026-04-19 00:58:27 UTC

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Let us gaze up the keyboard's battery hole
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/654/752/009/403/original/32ceb7420a4c2622.jpg

2026-04-19 00:56:47 UTC

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Disappointing mushy
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/647/263/771/358/original/21b61e7cb53d9809.mp4

2026-04-19 00:53:01 UTC

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Let's look in all the PCjr's orifices
#retrocomputing

2026-04-18 23:05:30 UTC

Unlike my floppy drive box, only a single goat has pissed on my PCjr box
#retrocomputing #vcf
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/428/208/879/611/627/original/b4cf4a280ad1ef76.jpg

2026-04-18 22:25:50 UTC

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The Tandy 1000 floppy controller does not have an external floppy connector. So where does this connect to?

2026-04-18 22:07:29 UTC

Another #vcf score, a Tandy 1000 external floppy drive. The box looks like a herd of goats pissed on it*!
*this is not why I bought it
#retrocomputing
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/427/980/092/398/732/original/5a3b0533cdd58981.jpg

2026-04-17 03:16:20 UTC

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This hobby needs fewer people hoarding stuff in storage rooms, and more people pulling it out and taking some damn photos of it all.

2026-04-17 03:14:00 UTC

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Enjoy the luxury of having a 50 year old computer. But it *is* a luxury.

2026-04-17 03:13:25 UTC

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The way that future generations will experience the computers that we grew up with will be via emulation. They might see an IBM 5150 in a museum, they will likely never sit down and be able to use one.

2026-04-17 03:12:43 UTC

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Your kids are likely going to throw your collection away, and if they don't, the kids of the people who sell your collection to likely will.
Fifty years from now there's really good odds that your entire retro computer collection is going to be buried 500 ft down in a landfill.

2026-04-17 03:11:42 UTC

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But if you're going to have some snide comment about emulation being inferior to the real thing, then I will definitely be asking what you have personally done to contribute to the preservation of the thing that you claim to love so much, since now you apparently have an opinion to share.

2026-04-17 03:11:20 UTC

I have a bit of a hot take.
If you're in the retro computer hobby just to tinker with stuff, to occasionally boot up your system for ten minutes of Prince of Persia every three months, there's nothing wrong with that.
Nobody expects you to do actual research or hack on things or document anything. The people that do that, do it because they have the time, motivation and a different set of goals.
#retrocomputing

2026-04-12 18:42:42 UTC

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well they still make those db-25 jumper boxes so you're in luck!

2026-04-12 18:27:43 UTC

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wiring up a little DE-9 to dupont adapter since I do this sort of thing often enough.
hsync is yellow (orange also acceptable) and vsync is either purple or blue.
if you pick any other colors you are clearly wrong

2026-04-12 17:14:54 UTC

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i figure this might be useful as a clock generator in general, so made a nice little help menu that prints when your terminal connects.
maybe we can support controlling the reset logic via micropython on the other core at some future point
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/392/851/843/457/425/original/d14db3150b8234cf.png

2026-04-12 16:59:21 UTC

What can I do with five IBM PC floppy controllers?
#retrocomputing
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/392/795/438/366/260/original/4414eb05340a0a27.jpg

2026-04-12 16:48:03 UTC

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It's really nuts how much functionality is packed into these little microcontrollers. But it makes configuring them a bit obtuse.
Here's the code that (I hope) configures GPIO pin D11 to act as an external reset line for Timer 8:<code> // CH2 = input capture mapped to TI2, used as DEN trigger source TIM8->CCMR1 &= ~( TIM_CCMR1_CC2S_Msk | TIM_CCMR1_IC2PSC_Msk | TIM_CCMR1_IC2F_Msk ); TIM8->CCMR1 |= TIM_CCMR1_CC2S_0; // CC2 mapped to TI2 // Apply a modest digital filter (fSAMPLING = fDTS, N = 8) to ignore noise TIM8->CCMR1 |= (0x3UL << TIM_CCMR1_IC2F_Pos); TIM8->CCER |= TIM_CCER_CC2E; </code>

2026-04-12 16:42:57 UTC

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I've got the Arduino sketch set up so that I can just hit keys in the serial terminal to adjust the clock parameters, which is pretty cool.
'f' makes the clock faster, 's' makes the clock slower, 'g' toggles the STM32's GPIO driver speed, which only has subtle effects at these frequencies.

2026-04-12 16:37:42 UTC

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Because I want a rainbow across the ENTIRE screen, dammit.

2026-04-12 16:37:03 UTC

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Eventually I will need to use something other than DEN to control the select input on our little 157.
I'm thinking Pin 6 on U43, which is the same chip we socketed to override the color clock, is a good candidate.
this is the inverted color burst trigger, and conveniently it isn't connected so we can solder on to the back of it.
so in theory, when pin 6 goes high, the color burst should be over and it should be safe to swap out our color clock.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/392/699/444/681/419/original/2379ac5cb3dd1818.png

2026-04-12 16:18:07 UTC

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I've been digging around in the STM32 datasheets, and I think I may have a solution for our synchronization problem.
We want to restart the STM32's Timer 8 each scanline so we get a deterministic color clock on each scanline, so that whatever whacky hue effect results is vertically aligned across the whole screen.
The timer has an external ETR input that can be used to reset the timer counter. We can feed this the HSYNC signal from the RGBI output since we're not using that in composite mode anyway.

2026-04-12 16:01:04 UTC

It turns out there is one clock the STM32 can generate from a 240MHz IO clock that is an even divisor of CGA scanlines.
The rainbow shimmer on the fence is a promising taste of what a Rainbow CGA should look like.
#retrocomputing #circuitbending
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/392/553/942/124/873/original/a1f34e9c2f04b02d.mp4

2026-04-11 21:13:40 UTC

if you buy a bunch of a stuff for a project, get a box, and as the stuff arrives, put the stuff for the project in that box. you can mark the box "box for stuff for the project."
then when you start the project, you will have all the stuff you need for the project. it will be in the box, because you put it there.
and you won't be me right now

2026-04-11 17:09:35 UTC

tweaked the palettes a bit, here are three pixel-art computers so far
#retrocomputing #pixelart
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/387/173/232/617/173/original/cb75f472bdbb51fb.png

2026-04-11 00:43:01 UTC

some CGA cards are kiki and some are bouba
#retrocomputing
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/383/292/749/184/528/original/02a9c7b06fc301fc.png

2026-04-10 22:58:31 UTC

Not sure I've ever seen the box for a IBM Model F keyboard ]before.
#retrocomputing
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/382/881/168/877/184/original/e6fed2e141832114.png

2026-04-10 19:21:42 UTC

Also started a pixel art 5150.
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/382/031/735/480/274/original/de0b8c3fb4af0ce8.png

2026-04-09 00:22:16 UTC

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doesn't your slicery thingy do that?
i don't know anything about 3d printing

2026-04-08 19:08:46 UTC

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And IBM PCjr!
https://www.freepoly.org/portfolio-1/ibm-pcjr-4863-computer
#retrocomputing #pcjr
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/370/655/726/734/534/original/d0b1b90a65276a29.png

2026-04-08 19:07:17 UTC

Some nice free models from freepoly.org:
First, we have a Tandy 1000
https://www.freepoly.org/portfolio-1/ibm-tandy-1000
#retrocomputing #tandy1000
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/370/648/597/098/546/original/1a29ecf1dd00980d.png

2026-04-08 13:19:58 UTC

Time to replace the bad power switch in my Commodore 1084D monitor!
#retrocomputing
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/369/284/095/864/254/original/4c9a06f43e9033cf.jpg

2026-04-08 00:09:58 UTC

My PC emulator MartyPC isn't enormously popular, but that's fine. I still find an occasional reference to it out in the wild internet yonder, which always makes my day.
So I was very happy to find this tutorial on programming mouse support in assembly language!
#retrocomputing #emulation
https://www.youtube.com/watch?v=_pps7LrvfSU

2026-04-05 04:00:50 UTC

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I think my first exposure to them was a demo of what was almost certainly a Fairlight CMI on the show "Reading Rainbow." In fact, hold on, I bet that shit's on youtube.
YUP
https://youtu.be/AjxX2ey53hg?t=105

2026-04-05 03:59:07 UTC

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that is my legitimate interest in them. they feel like something that fell down between the stairs of my childhood memories. something known in the abstract but never seen or felt.
i gotta admit I got a little tingle the first time i touched a button with the pen and the software responded.

2026-04-04 22:51:27 UTC

For the first time in maybe - decades? Someone has a complete, high-resolution CGA light pen system for the original IBM PC.
(It's me. I'm the someone)
#retrocomputing #lightpen
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/348/874/780/388/444/original/cd0547b1673a5db9.png

2026-04-04 19:32:36 UTC

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right, it won't prevent a manual conversion.
i was just thinking if you could get the correction perfect, you could do a nearest neighbor shrink down to 1x1 and then clean it up a bit

2026-04-04 19:26:41 UTC

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this is just really tricky...
I run into this a ton correcting photos of PCBs and then noticing stuff shift in the middle when i'm tracing it out.
it's easy to get the edges aligned but still have drift in the center.
The thing is i'm wondering if "barrel distortion" in terms of what a lens captures is geometrically equivalent to a CRT's curvature. I'd bet it isn't 1:1
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/348/070/450/723/725/original/a9a849fd0353e9a2.png

2026-04-04 19:20:29 UTC

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can you explain how you did that? i figure i need a lens correction tool with an arbitrary center point, photoshop assumes you are working on a full-frame image from a camera

2026-04-04 19:19:13 UTC

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hey, that's pretty good!

2026-04-04 18:19:41 UTC

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yes this is about lenipen but it just got me thinking.
the text at the bottom of the screenshot is your standard 40 column 8-pixel CGA font, so that gives a clear reference for everything else.
There is enough resolution here to reconstruct the image, but it will be laborious.
I tried to cancel the barrel distortion, but it's awkward because it's not centered -the line of text at the bottom is straight, but the menu headers at the top are curved up.
I've always been curious how these magazines took screenshots...
https://assets.oldbytes.space/assets.oldbytes.space/media_attachments/files/116/347/806/336/207/075/original/e7d24fe2e3d47e03.png

2026-04-04 18:15:38 UTC

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making the training set would be a bit of a pain - i was thinking about finding screenshots that you could reproduce in an emulator, but maybe just taking screenshots and putting them through some print-process simulation with barrel distortion, halftone dots and bit of the 'ol gaussian blur

2026-04-04 18:14:03 UTC

@npub1g8x…7wul
I wonder if you could train a CNN to map a printed screenshot from a magazine back to the exact pixels
#retrocomputing

2026-04-03 23:55:15 UTC

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hey cataract buddy, the surgery is really fast and painless, i'd rather have cataract surgery again than go to the dentist