int10h.org - VileR's blog

A Lost IBM PC/AT Model? Analyzing a Newfound Old BIOS

Wed, 05 Nov 2025 09:07:01 +0200

It's not every day that a yet-unknown set of PC-family BIOS ROMs surfaces after 4 decades in obscurity. This one sure is strange, and seems to confirm accounts of a certain cancelled PC/AT prototype. It might also explain a bit of weirdness in some of IBM's published BIOS listings.

Those Secret Fonts from the ISA-16 PS/2 Models (Again)

Sat, 26 Jul 2025 18:56:43 +0300

Those four 'bonus' screen fonts in the ROM BIOS of the IBM PS/2 Model 30-286 (and friends) have some more history behind them than was uncovered in my earlier post. How did they get there, where from, and who the heck is Howard?

Missing IBM PC Localization Disks & ROMs

Sun, 06 Oct 2024 23:59:38 +0300

Some answers emerge about IBM's original 'Nordic' code page for the PC. Rather predictably, we're left with even more questions... including a long list of CGA/MDA character ROMs and NLS (National Language Support) diskettes which are still not accounted for.

Name the Non-Standard PC Code Page

Wed, 07 Aug 2024 11:43:47 +0300

Imagine you're in South Africa or Brazil, and one day you wake up to find that your country has wedged itself firmly in the Nordics. What happened? Why, a wild 8-bit PC character set happened, of course! Let's see if we can make some sense of it.

Game Font Forensics

Sun, 11 Feb 2024 22:26:57 +0200

You might have picked up on two recurring topics around these parts: ancient PC games, and ancient bitmap fonts. This installment combines the two for fact-finding purposes, and possibly sets some new records in going down silly rabbit holes, but it's all about what you learn along the way!

Astro-Dodge's Dirty Video Tricks

Fri, 20 Oct 2023 20:35:24 +0300

This is what happens when you don't resist the urge to poke at old games with sharp sticks. You get 1 (one) ancient Asteroids clone for the IBM, a whole bunch of variations on a positively bonkers video mode, and a complimentary detour on the trail of a non-PC version, because that's how we roll.

Raising the Bar for IBM PC/XT Emulation: MartyPC

Wed, 05 Jul 2023 17:37:21 +0300

This was publicly released over a month ago, so it's old news by now; but the IBM PC has waited over 4 decades to be emulated quite this faithfully, so what's a little holdup between friends? MartyPC is the latest breakthrough in emulating the 5150 and 5160 - here's why I like it, and so will you.

More CGA CRTC Glitching: HD6845(R) vs. MC6845

Sat, 22 Apr 2023 12:36:31 +0300

We've seen how the MC6845 CRTC can produce unintended, 'phantom' vertical sync pulses if R7 is rewritten during active display time. How about the HD6845? Well, Hitachi's 6845 variant appears to be more sensitive, and will glitch in even more cases than its Motorola counterpart.

Old Chips, New Glitches: the CGA/CRTC "Phantom" VSync

Tue, 21 Mar 2023 09:18:31 +0200

A dive into an obscure hardware glitch in the 6845 CRTC chip, which has to do with register rewriting, and only seems to really have a noticeable effect on IBM CGA boards (so far). Let's see what it is, why it occurs, and how to avoid it. There's bonus fractals, too!

The IBM 5153's True CGA Palette and Color Output

Sat, 11 Jun 2022 03:32:05 +0300

CGA can output 16 digital RGBI colors, and there's a well-known standard palette which translates them to (s)RGB values - but that palette isn't a very good approximation of the colors you actually get on IBM's original CGA monitor. Why is that, and can we do better?

About the PS/2 30-286's Hidden VGA Fonts

Sun, 05 Jun 2022 21:11:12 +0300

Another old riddle bites the dust: why did some 16-bit ISA PS/2 machines have an extra set of four alternate fonts tucked away in their firmware? What on earth were those fonts good for? And what's one thing you should never do when you're a PC developer 35 years ago?

'Space Covidders' Goes to the Arcade?

Sun, 28 Nov 2021 22:37:05 +0200

A little hack of Space Commanders from last year gets an unexpected (and awesome) makeover, courtesy of someone else's talent.

Safe CRT Monitor Shipping: IBM 5153 Makes it through DHL!

Thu, 08 Apr 2021 14:44:26 +0300

Believe it or not, it's possible to transport ancient CRTs across continents, even with today's shipping services pulling out all the stops on incompetence. Here's how an IBM Color Display was packed, shipped, and lived to tell the tale.

Simulating NON-CRT Monitors with FFmpeg: Flat Panel Displays

Wed, 03 Mar 2021 00:09:44 +0200

CRTs get all the retro-hype, but oldschool portable PCs had slimmer alternatives: monochrome/grayscale LCDs, orange plasma panels, and yellow electroluminescent ones. Why not add those too, and throw in a little bonus tool to emulate how some of them faked grayscale "shading" on 1-bit monochrome?

Simulating CRT Monitors with FFmpeg (Pt. 2: Monochrome CRTs)

Wed, 03 Feb 2021 23:43:17 +0200

As Kermit the Frog and his IBM 5151 display once commiserated with Greta Thunberg, "it's not easy being green". This update here should make it less difficult - and there's also amber, various shades of white, and a few more settings you can tweak.

Simulating CRT Monitors with FFmpeg (Pt. 1: Color CRTs)

Sun, 10 Jan 2021 18:29:21 +0200

...or: Who needs shaders - just do it the slow way! A Windows batch file with a bunch of tunable options, so you can apply the effect to a still image or a video, and still be back in time for dinner (or the next geological epoch, whichever comes last).

More Font Updates: Oldschool PC Pack, Flexi IBM VGA

Tue, 01 Dec 2020 23:23:23 +0300

Yet another load of pixellated character sets, converted from classic PC-related hardware for your enjoyment. And for the sake of balance, a decidedly non-pixellated update of an old mainstay.

Git Push

Wed, 16 Sep 2020 17:21:09 +0300

Code projects are now hosted on GitHub, so you all get shiny new download links to match. Also: a Fontraption update, and a split in the ranks.

Ultimate Oldschool PC Font Pack v2.0 Released

Mon, 13 Jul 2020 12:25:18 +0300

To make up for the 4-year holdup, it's quite a big update: 133 new font families (from 52 different sources), 3 new variants for each font (.ttf w/embedded bitmaps, aspect-corrected .ttf, and .woff for the web), and a revamped website to hold all of these (somewhat) together.

Auto-Injecting Files into an Active PCem/86Box Machine

Wed, 15 Apr 2020 12:19:00 +0300

A tool for quick and painless file transfers from host to guest. No need to restart the emulated machine, to create temporary images manually, or to set up any kind of networking: one click, and your files go through.

Fontraption (a VGA Text Mode Font Editor)

Wed, 22 May 2019 23:56:31 +0300

A new font editor for DOS: dual tab interface, clipboard, block operations, 40/80 columns, 8/9-dot mode. Handles ROM + BMP + XBIN formats, and can create configurable .COM TSRs. All in a 12KB executable (source is included, plus a huge pack of fonts).

De-uglifying 40-Column Text Games for VGA

Thu, 16 May 2019 01:16:53 +0300

Does VGA 40-column text mode hurt your eyeballs and disfigure the games you play? A couple of small, mode-specific font replacement TSRs to the rescue.

TVCGAFIX Utilities - Adjust CGA Output for TV

Wed, 08 Aug 2018 01:51:28 +0300

Using a TV set as a CGA display device has its issues, especially horizontal centering and color in 80-column text mode. These utilities should help. There's a bootable version too, so you can throw it at your favorite booter games.

Taking Decent Photos of your CRT TV Screen

Sat, 16 Jun 2018 23:37:28 +0300

A few techniques derived by trial-and-error, and some obvious pitfalls to avoid. May prove useful to you other amateur CRT photographers out there.

Flexi IBM VGA Font: a Scalable Take on Text Mode

Wed, 23 May 2018 00:01:21 +0300

Yet another go at converting the pre-GUI PC's most iconic typeface into a TrueType font. This time, a version with scalable outlines and a faithful aspect ratio.

So Long, Blogspot

Sat, 05 May 2018 16:45:28 +0300

How to migrate away from a centralized, restricted platform and keep your cool and your "link juice" (disclaimer: retainment of cool may vary).

Steel Survivor: an IBM XT Tale

Thu, 29 Mar 2018 22:58:37 +0300

A fully-equipped IBM 5160 braves the rigors of international shipping and gets here in one piece (just barely). As will be pictorially demonstrated, 30+ years after leaving the factory, this steel warrior is still one tough SOB.

Happy 35th birthday, IBM PC!

Thu, 18 Aug 2016 16:28:29 +0300

My present: 'Sorry Ass' - a 512-byte boot sector version of Bill Gates' DONKEY, the infamous demonstration game included with DOS and BASIC 1.0.

Keen 4 Mystery Code Demystified

Mon, 18 Jul 2016 02:32:37 +0300

A little bit of reverse-engineering fun. Why was a seemingly-unused routine left over in Commander Keen 4's executable code, and does it do anything useful? Let's find out!

Yet another 16-color CGA makeover: Keen 5

Mon, 18 Jul 2016 02:08:51 +0300

After giving Keen 4's CGA version a 16-color composite overhaul, I figured I'd have a go at the next episode. More custom code and graphics for the artifact-color aficionado.

Dopefish goes NTSC: Commander Keen 4 Composite CGA Patch Notes

Sun, 29 May 2016 02:40:51 +0300

This game is a pretty impressive piece of CGA programming, but there's one thing it doesn't do: exploit NTSC quirks to get 16 colors on a TV/composite monitor, instead of the familiar 4. Here's how you can change that with a patch and a custom set of converted graphics.

Olympiad: IBM Prototype Fonts Unearthed

Wed, 23 Mar 2016 01:36:46 +0300

Historical exhibit: a set of 25 floppy disks documenting IBM's creation of an in-house bitmap typeface for the RT PC project (code-named Olympiad). Contains the original material as received, plus TTF and PNG conversions of the fonts and images.

So-called "IBM" Freeware Games from the Early '80s

Fri, 26 Feb 2016 12:02:11 +0300

An archeological riddle: these very early public domain games all have similar title screens, which say "IBM" although they were clearly homebrew creations. Where do they come from, who made them, and what is that cryptic "mystery code" all about?

The Ultimate Oldschool PC Font Pack (v1.0)

Sun, 17 Jan 2016 01:07:06 +0300

Presenting the world's biggest collection of classic text mode fonts, system fonts and BIOS fonts from the DOS-era IBM PCs and compatibles. Contains TrueType (TTF) and bitmap (FON) versions of the original character sets, and some unicode expansions as well.

Windows (and ClearType) vs. Truetype Fonts with Embedded Bitmaps

Fri, 08 Jan 2016 00:11:23 +0300

Is it possible to get Windows to display TrueType pixelfonts in a crisp bitmap-like fashion? Technically, yes. Practically... not really.

BigBlue Terminal: An Oldschool Fixed-Width Pixel Font

Fri, 18 Dec 2015 19:51:40 +0300

Compact just like Windows' Terminal font, but based on the EGA/VGA text mode character sets. Comes in TrueType and bitmap versions. Besides good ol' codepage 437, it also supports an expanded unicode charset.

Getting Optimal Apple ][ Screenshots w/NTSC Emulation

Sun, 08 Nov 2015 17:04:54 +0300

Most Apple ][ emulator screenshots out there completely misrepresent the color and resolution of that machine's composite video output. Here's how to fix that.

101 Monochrome Mazes: Why Not Color?

Sun, 09 Aug 2015 16:31:32 +0300

IBM officially discouraged PC programmers from exploiting hardware-specific tricks, since that came at the expense of compatibility. Then, they went and released a game that did just that. Here's why it was (artificially) prevented from running on color systems.

8088 MPH Final: Old vs. New CGA (and Other Gory Details)

Fri, 07 Aug 2015 03:39:06 +0300

Another installment on CGA display tricks - covering the final version of 8088 MPH, determining the model of your CGA card in wetware, the extended 1024-color palettes supported by both models, and some artistic considerations.

New Design

Mon, 03 Aug 2015 08:14:28 +0300

Not so new anymore.

CGA in 1024 Colors - a New Mode: the Illustrated Guide

Wed, 15 Apr 2015 23:56:27 +0300

Can you take the original IBM PC color graphics board, and force it to display 32 times as many colors as it's officially capable of? Believe it, comrade! Here's the in-depth write-up on how we did that in the 8088 MPH demo, complete with illustrations.

Arithmetic Games Set 1: a Peek into One of the First-Ever IBM PC Games

Fri, 16 May 2014 02:54:46 +0300

Back in 1981, this was part of the original set of software available for the IBM PC on launch. As it turns out, its roots go even earlier than that - and there's also the easily-bypassed copy protection, and a mysterious check for a BASIC error code that isn't documented anywhere.

Shamus Keyboard Woes Explained

Tue, 13 May 2014 13:43:38 +0300

The lowdown on why this game can be so frustrating to play with the keyboard - in the wrong circumstances.

The Mazes of Shamus - IBM PC Version

Mon, 21 Oct 2013 07:28:51 +0300

Mapping out all four levels and 127 rooms of this maze shooter - specifically, the IBM PC version. As proof of cartographic accuracy, you also get a playthrough video.

Using Photoshop as a CGA Bitmap Paint Program

Sat, 12 Oct 2013 22:38:27 +0300

An exercise in taking "modern" graphics software and dragging it kicking and screaming back to the glorious days of clean, simple, 2 bits per pixel raster graphics. Plus a time-lapse video of the whole process.

Power-On Self-Test...

Fri, 11 Oct 2013 02:06:43 +0300

64 KB OK