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- Related ongoing thread:
80386 Microcode Disassembled - https://news.ycombinator.com/item?id=48247004 - May 2026 (42 comments)
by dang - 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
- 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 - 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
- There's likely plenty of them still in use in industrial/embedded applications.by userbinator
- I think there are industrial pcs with a 486-compatible soc.
A ton of industrial equipment are still using win 3.1.
by geon - 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 - Did the microcode disassembly find any useful backdoors to read microcode without decapping?by mmastrac
- there are several iterations of 386 and only one was disassembled
so there's still a chance
by NooneAtAll3 - 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
- Kind of surprised this only takes 18K LUTs. That's a fairly small FPGA these days.by UncleOxidant
- 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.by mycall
- Related:
80386 Microcode Disassembled
- 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.
by cbdevidal - haha, this was my first thought when I read the headline, because this "classic test" always comes up here :-))
- 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
- 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