alt.hn

5/23/2026 at 2:25:30 PM

z386: An Open-Source 80386 Built Around Original Microcode

 https://nand2mario.github.io/posts/2026/z386/

by wicket

5/23/2026 at 4:05:36 PM

Of course they tested Doom :-D

They might also run Linux kernel 3.7, that supported i386. Gray386linux is still maintained, and runs a patched 3.7 kernel.

https://github.com/marmolak/gray386linux

by cbdevidal

5/23/2026 at 4:35:17 PM

Doom (DOS extender games) is an easier protected mode application as it does not use complex page tables. Linux is much more complex.

by nand2mario

5/23/2026 at 4:38:37 PM

I have faith in you!!

by cbdevidal

5/24/2026 at 1:39:05 AM

If modern x86 microcode ever gets sufficiently understood and reverse engineered I bet someone gets a PLAYDOOM instruction working. (I know it's been at least partially implemented on FPGAs)

by RiverCrochet

5/23/2026 at 4:14:27 PM

haha, this was my first thought when I read the headline, because this "classic test" always comes up here :-))

by KellyCriterion

5/23/2026 at 4:48:47 PM

Kind of surprised this only takes 18K LUTs. That's a fairly small FPGA these days.

by UncleOxidant

5/23/2026 at 5:37:10 PM

How does it compare to something like VexRisc [0] with respect to its capabilities? I know having x86 support is a metric all by itself.

[0] https://github.com/spinalhdl/vexriscv

by mycall

5/23/2026 at 11:30:44 PM

No contest really: RISCV is a much better ISA, VexRISC is a hyper-optimised implementation of it (for FPGAs), and it's not hindered by trying to be microcode compatible.

The roughly equivalent VexRISC configuration (full with MMU) is only 2736 LUTs, running at 124 Mhz (on Cyclone V, which I'm pretty sure is the same arch)

by phire

5/23/2026 at 3:21:13 PM

Did the microcode disassembly find any useful backdoors to read microcode without decapping?

by mmastrac

5/23/2026 at 3:28:07 PM

Not really. The 386 does not have an interface to read the ROM direclty. Instead, it uses the Built-In Self-Test (BIST) to verify the ROM's contents. It's basically a checksum-like mechanism that verify the integrity of the CROM.

by nand2mario

5/23/2026 at 6:26:28 PM

there are several iterations of 386 and only one was disassembled

so there's still a chance

by NooneAtAll3

5/23/2026 at 4:16:59 PM

Question: Are there today any 386 instances running somewhere in the basement to do some productive stuff, maybe processing only some controller data once a day?

I remember the link some month ago where that one small shop ran completely on an old Amiga (?IIRC, not sure, was linked here)

Around 98/99 I was involved in a small IT-management company serving SME around the region, we had a client producing distinct metal objects with a big press; this got feeded once a day with a 5.25 floppy from another machine with production data - and it was still in use while we had already ethernet/USB/3.5 floppies etc. :-D

by KellyCriterion

5/23/2026 at 6:26:06 PM

I think there are industrial pcs with a 486-compatible soc.

A ton of industrial equipment are still using win 3.1.

by geon

5/23/2026 at 6:41:09 PM

Consequence of the 'if it works, why mess with it?' mindset. It will become a problem when those boards give out and spares are gone.

by bzzzt

5/23/2026 at 8:20:31 PM

I wonder how many of those are actually still out there. According to Wikipedia, Intel kept making replacement parts (386 and 486) until September 2007, but personally, I have never come across one in actual use. My own career in this field began with an internship in 2008. My day job includes working on a PLC runtime with a code base older than myself, originally written for DOS, but every industrial PC (or other x86 based embedded device) I have ever got to play around with had at the very least a Pentium class CPU in it.

As for the Windows 3.x based industrial equipment: Some industrial devices I have worked on in the past turned out to actually be ARM based, running Linux, but the software went a long way to convincingly fake old Windows style UI or emulate a DOS prompt. I was once tasked to extend such a UI library to faithfully reproduce Windows 98 style color gradient borders.

Only once have I seen an actual embedded 486SX with my own eyes, but not in active use anymore. Last year, someone dragged a dusty, old, weirdo Siemens telephony box to the the local Hackerspace. The box itself had a design language that screamed "Star Trek: Voyager". I found a UART, it was running "On Time RTOS-32" which, according to the German Wikipedia, was an RTOS with a Windows API compatible userspace, developed by a German company in 1996 and discontinued in 2023.

by st_goliath

5/23/2026 at 10:03:52 PM

> Some industrial devices I have worked on in the past turned out to actually be ARM based, running Linux, but the software went a long way to convincingly fake old Windows style UI or emulate a DOS prompt. I was once tasked to extend such a UI library to faithfully reproduce Windows 98 style color gradient borders.

IBM mainframes have an embedded PC (the "Support Element") used to manage the hardware configuration and diagnostics. Originally, it ran OS/2. In 2005, IBM replaced it with Linux–running a UI which looked like OS/2. (At some point more recently, they refreshed the visual look so it doesn't look like OS/2 any more, although I'm not sure when they did that.)

by skissane

5/23/2026 at 10:30:17 PM

No. That’s why companies like Vortex are still in business. There’s even a company producing new Win98 machines for this reason.

by BirAdam

5/23/2026 at 5:21:16 PM

There's likely plenty of them still in use in industrial/embedded applications.

by userbinator

5/23/2026 at 4:26:11 PM

A few years ago there was a story where the single Amiga that ran an entire US school district's HVAC was replaced with a system costing like 1.5 million dollars, after 30 years of dutiful service.

I can't think of examples offhand but you bet your ass there are donut shops and auto body repair services running 386s to do POS, inventory, and the like. Some of them may be driving terminals off Xenix.

by bitwize

5/23/2026 at 4:54:37 PM

Funny thing about this is that the character-based systems of that era, whether PC-type or host+terminal type, were most of the time so much faster and more responsive than the laggy, over-animated, touchscreen trash they always replace them with in order to get big screens and prettier graphics.

by xp84

5/23/2026 at 5:53:20 PM

The Amiga was not character-based, it ran an accelerated framebuffer (with support for scanning out multiple resolutions and color depths on a single screen).

by zozbot234

5/23/2026 at 7:23:33 PM

Sorry, I was generalizing the "typical" pre-1995 system one would find in commercial installations, which in general were character-based. But I'm sure the Amiga solution would have been nice and fast too, since they were pretty powerful and programmers back then didn't feel the need to bring in PhoneGap, React, or 5,280 npm packages in order to display what amounts to a form.

by xp84

5/23/2026 at 7:48:51 PM

RE "....a system costing like 1.5 million dollars, after 30 years of dutiful service....."

I immediately wondered ... how long the new system would last or be used .... and how long it would be problem free ?

by asdefghyk

5/24/2026 at 5:32:28 AM

Ultimately that kind of question doesn't really matter. The only question that matters is "who will fix it when it breaks?" The Amiga system was a single machine running custom code written by one guy. If that guy dies or decides to quit maintaining it and it fails, hundreds of school kids are going to end up shivering or overheating for who knows how long. That's an unpleasant risk that may prove more costly than the $1.5mil it cost to replace it. The new system was written by a team, working at a company that specializes in this sort of thing, that has credentials proving it complies with relevant industry and safety standards, and a contract binding it to a term of service and support. That shit's worth its weight in gold to businesses and governments, even though it doesn't necessarily result in added functionality. So while it's fun to post "look at what they need to mimic a fraction of our power" memes about old systems like that, there's a reason why these are done by teams working at institutional organizations. It helps defray the risk.

In the late 90s I was interning at a place, and one of the IT guys there was old, we're talking white beard. He thought Linux was an absolute joke, and told me that the future of IT belonged to Windows NT (though it should have belonged to OS/2). The reason why is because with Linux, there was "no ass to drag onto the carpet"—no one to sue when it breaks. With Windows, the largest and most successful software company of all time was backing it up, staking their entire business on customer satisfaction. Of course, he ended up being wrong about Linux, but only because companies (mainly Red Hat) stepped up to assume the risk for big clients. That's one of the major functions of business—to provide an arm for customers to twist.

by bitwize

5/23/2026 at 11:31:15 PM

You missed a fun part of that story! The person who programmed it was a kid in the district at the time. They continued to hire him to come back and maintain it any time they had issues, which apparently was fairly rare.

by AviationAtom

5/24/2026 at 6:04:13 AM

And back in the 90s, before anybody knew anything about risk or "bus factor", that might've made sense. But it's no surprise that they paid a pretty penny for an actual support contract after decommissioning that system.

by bitwize

5/24/2026 at 5:23:09 AM

Sadly, without an accompanying FPGA-implementation of an FPU it's much less useful for productivity work/research, i.e. outside of 08/15 gaming and application fare. Same with Ao486, which only implements a 486SX.

by spankibalt

5/24/2026 at 7:18:31 AM

I think there are two reasons we haven’t seen an FPGA FPU yet, especially for MiSTer.

First, FPUs are complex and FPGA support for floating point is limited. There's DSP blocks for integer additions and multiplications. But very little FP support.

Second, the CPU itself may not be fast enough for an FPU to matter much. Quake wants at least a 75 MHz Pentium, while ao486-MiSTer is closer to a 486-66. So we probably need both a faster CPU design and a faster FPGA. Maybe Altera's new Agilex 5 will be useful here.

by nand2mario