z386: An Open-Source 80386 Built Around Original Microcode
z386: An Open-Source 80386 Built Around Original Microcode
Hackaday Article
hackaday.com
May 25, 2026 at 11:03 PM
z386: An Open-Source 80386 Built Around Original Microcode
writing microcode (8pt font size)
March 20, 2026 at 9:46 PM
writing microcode (8pt font size)
The Intel 8087 and Conditional Microcode Tests
The Intel 8087 and Conditional Microcode Tests
Hackaday Article
hackaday.com
January 11, 2026 at 3:08 PM
The Intel 8087 and Conditional Microcode Tests
Credits: I've been working on this with the members of the "Opcode Collective", especially Smartest Blob and
@gloriouscow.bsky.social, who used ML to convert ROM images to microcode data and extensively analyzed the contents.
7/7
@gloriouscow.bsky.social, who used ML to convert ROM images to microcode data and extensively analyzed the contents.
7/7
September 26, 2026 at 5:00 PM
Credits: I've been working on this with the members of the "Opcode Collective", especially Smartest Blob and
@gloriouscow.bsky.social, who used ML to convert ROM images to microcode data and extensively analyzed the contents.
7/7
@gloriouscow.bsky.social, who used ML to convert ROM images to microcode data and extensively analyzed the contents.
7/7
We are reverse-engineering the meaning of the 8087's microcode. For more details, see my latest article:
www.righto.com/2026/05/micr...
www.righto.com/2026/05/micr...
Microcode inside the Intel 8087 floating-point chip: register exchange
In 1980, Intel introduced the 8087 floating-point chip, a co-processor that made floating-point operations up to 100 times faster. This chip...
www.righto.com
May 30, 2026 at 5:42 PM
We are reverse-engineering the meaning of the 8087's microcode. For more details, see my latest article:
www.righto.com/2026/05/micr...
www.righto.com/2026/05/micr...
The Pentium processor, like many others, implements its instructions in microcode. Each step of an instruction is described by a micro-instruction, stored in the chip in the microcode ROM.
This die photo shows the parts of the Pentium. Let's take a quick look at the microcode ROM...1/N
This die photo shows the parts of the Pentium. Let's take a quick look at the microcode ROM...1/N
March 31, 2025 at 5:40 PM
The Pentium processor, like many others, implements its instructions in microcode. Each step of an instruction is described by a micro-instruction, stored in the chip in the microcode ROM.
This die photo shows the parts of the Pentium. Let's take a quick look at the microcode ROM...1/N
This die photo shows the parts of the Pentium. Let's take a quick look at the microcode ROM...1/N
AMD: Microcode Signature Verification Vulnerability github.com/google/secur...
AMD: Microcode Signature Verification Vulnerability
### Summary
Google Security Team has identified a security vulnerability in some AMD Zen-based CPUs. This vulnerability allows an adversary with local administrator privileges (ring 0 from outside...
github.com
February 3, 2025 at 7:51 PM
AMD: Microcode Signature Verification Vulnerability github.com/google/secur...
Intel announced the 8087 floating-point chip in 1980. Now I have a blog post that explains a small part of the microcode in this chip.
www.righto.com/2025/12/8087...
www.righto.com/2025/12/8087...
Conditions in the Intel 8087 floating-point chip's microcode
In the 1980s, if you wanted your computer to do floating-point calculations faster, you could buy the Intel 8087 floating-point coprocessor ...
www.righto.com
December 30, 2025 at 7:54 PM
Intel announced the 8087 floating-point chip in 1980. Now I have a blog post that explains a small part of the microcode in this chip.
www.righto.com/2025/12/8087...
www.righto.com/2025/12/8087...
The 8087 chip implements its algorithms in microcode, specialized low-level code inside the chip. By examining the microcode ROM under a microscope, the Opcode Collective extracted the bits and I reverse-engineered the algorithm.
September 26, 2026 at 5:00 PM
The 8087 chip implements its algorithms in microcode, specialized low-level code inside the chip. By examining the microcode ROM under a microscope, the Opcode Collective extracted the bits and I reverse-engineered the algorithm.
In the 1980s, if you wanted your IBM PC to be faster for spreadsheets or CAD, you could buy the Intel 8087 floating-point chip. Internally, the chip runs special code called microcode. We opened the chip, extracted the microcode, and are figuring out how it works. 1/n
May 30, 2026 at 5:42 PM
In the 1980s, if you wanted your IBM PC to be faster for spreadsheets or CAD, you could buy the Intel 8087 floating-point chip. Internally, the chip runs special code called microcode. We opened the chip, extracted the microcode, and are figuring out how it works. 1/n
Read the story of how the NEC V20's microcode was decoded.
martypc.blogspot.com/2026/09/deco...
#retrocomputing #vintagecomputing #reverseengineering #x86
martypc.blogspot.com/2026/09/deco...
#retrocomputing #vintagecomputing #reverseengineering #x86
Decoding the NEC V20 Microcode
reenigne's decoding of the 8088 microcode in 2020 opened the doors for extremely accurate emulation of the 8088 CPU. Although I had added...
martypc.blogspot.com
September 3, 2026 at 8:39 PM
Read the story of how the NEC V20's microcode was decoded.
martypc.blogspot.com/2026/09/deco...
#retrocomputing #vintagecomputing #reverseengineering #x86
martypc.blogspot.com/2026/09/deco...
#retrocomputing #vintagecomputing #reverseengineering #x86
The 8087's microcode is too complicated and low-level to explain here. For details, see my latest article:
www.righto.com/2026/09/8087...
www.righto.com/2026/09/8087...
Microcode in Intel's 8087 floating-point chip: the scale instruction
In the 1970s, floating-point arithmetic was a mess. Computer manufacturers had a dozen incompatible arithmetic standards. Moreover, floating...
www.righto.com
September 12, 2026 at 4:24 PM
The 8087's microcode is too complicated and low-level to explain here. For details, see my latest article:
www.righto.com/2026/09/8087...
www.righto.com/2026/09/8087...
Decoding the NEC V20 Microcode ROM
Decoding the NEC V20 Microcode ROM
Hackaday Article
hackaday.com
September 9, 2026 at 11:09 AM
Decoding the NEC V20 Microcode ROM
There's only four things we do better than anyone else:
movies
music
microcode (software)
high-speed pizza delivery
--SNOW CRASH (1992)
movies
music
microcode (software)
high-speed pizza delivery
--SNOW CRASH (1992)
Generally the revealed preference of the Trump admin has been that the US should be a petro state with a software sector and maybe some low value added manufacturing somewhere.
October 27, 2025 at 4:03 PM
There's only four things we do better than anyone else:
movies
music
microcode (software)
high-speed pizza delivery
--SNOW CRASH (1992)
movies
music
microcode (software)
high-speed pizza delivery
--SNOW CRASH (1992)
Music, movies, and microcode.
July 5, 2026 at 6:51 PM
Music, movies, and microcode.
But also microcode
February 8, 2024 at 4:24 AM
But also microcode
Full details of EntrySign, the AMD Zen microcode signature validation vulnerability disclosed last month. bughunters.google.com/blog/5424842...
Blog: Zen and the Art of Microcode Hacking
This blog post covers the full details of EntrySign, the AMD Zen microcode signature validation vulnerability recently discovered by the Google Security team.
bughunters.google.com
March 5, 2025 at 11:46 PM
Full details of EntrySign, the AMD Zen microcode signature validation vulnerability disclosed last month. bughunters.google.com/blog/5424842...
Happy DEC-9!
Apropos nothing at all, I started on a simulation of the PDP-9 hardware, to spare anyone else from having to do that. 0/10 would not microcode again.
github.com/larsbrinkhof...
Apropos nothing at all, I started on a simulation of the PDP-9 hardware, to spare anyone else from having to do that. 0/10 would not microcode again.
github.com/larsbrinkhof...
GitHub - larsbrinkhoff/pdp9-microcode: PDP-9 simulation running original microcode
PDP-9 simulation running original microcode. Contribute to larsbrinkhoff/pdp9-microcode development by creating an account on GitHub.
github.com
December 9, 2024 at 6:20 AM
Happy DEC-9!
Apropos nothing at all, I started on a simulation of the PDP-9 hardware, to spare anyone else from having to do that. 0/10 would not microcode again.
github.com/larsbrinkhof...
Apropos nothing at all, I started on a simulation of the PDP-9 hardware, to spare anyone else from having to do that. 0/10 would not microcode again.
github.com/larsbrinkhof...
z386: Une implémentation du 386 pour FPGA conçue avec d'après le microcode original du microprocesseur
nand2mario.github.io/posts/2026/z...
nand2mario.github.io/posts/2026/z...
June 14, 2026 at 1:36 PM
z386: Une implémentation du 386 pour FPGA conçue avec d'après le microcode original du microprocesseur
nand2mario.github.io/posts/2026/z...
nand2mario.github.io/posts/2026/z...
Great deep-dive on AMD Zen microcode hacking and a signature-validation flaw
bughunters.google.com/blog/5424842357473280/zen-and-the-art-of-microcode-hacking
#infosec
bughunters.google.com/blog/5424842357473280/zen-and-the-art-of-microcode-hacking
#infosec
October 20, 2025 at 3:13 PM
Great deep-dive on AMD Zen microcode hacking and a signature-validation flaw
bughunters.google.com/blog/5424842357473280/zen-and-the-art-of-microcode-hacking
#infosec
bughunters.google.com/blog/5424842357473280/zen-and-the-art-of-microcode-hacking
#infosec
"Zen and the Art of Microcode Hacking"
Tragic signature bypass enables custom microcode loading on AMD processors, and a tool to do it. The blog is extremely well written and provides concise explanations of topics mentioned + plenty of resources! A must read.
bughunters.google.com/blog/5424842...
Tragic signature bypass enables custom microcode loading on AMD processors, and a tool to do it. The blog is extremely well written and provides concise explanations of topics mentioned + plenty of resources! A must read.
bughunters.google.com/blog/5424842...
Blog: Zen and the Art of Microcode Hacking
This blog post covers the full details of EntrySign, the AMD Zen microcode signature validation vulnerability recently discovered by the Google Security team.
bughunters.google.com
March 6, 2025 at 2:32 AM
"Zen and the Art of Microcode Hacking"
Tragic signature bypass enables custom microcode loading on AMD processors, and a tool to do it. The blog is extremely well written and provides concise explanations of topics mentioned + plenty of resources! A must read.
bughunters.google.com/blog/5424842...
Tragic signature bypass enables custom microcode loading on AMD processors, and a tool to do it. The blog is extremely well written and provides concise explanations of topics mentioned + plenty of resources! A must read.
bughunters.google.com/blog/5424842...
A microscope reveals the complex circuitry of the 8087 chip. The microcode ROM in the center holds the micro-instructions. It executes these micro-instructions to add, subtract, compute square roots, arctangents, and so forth. 2/n
May 30, 2026 at 5:42 PM
A microscope reveals the complex circuitry of the 8087 chip. The microcode ROM in the center holds the micro-instructions. It executes these micro-instructions to add, subtract, compute square roots, arctangents, and so forth. 2/n