Chris Williams
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diodesign.org
Chris Williams
@diodesign.org
400 followers 210 following 46 posts
Work: https://docs.cloud.google.com/
Personal: https://diodesign.org/
Wear sunscreen.
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diodesign.org
This was pretty interesting, hearing how the small team behind the 8-bit BBC Acorn computer went from specifying ULA chip designs to designing the early Arm CPU series from scratch using BBC BASIC

www.youtube.com/watch?v=W2yD...
From Acorn to ARM with Professor Steve Furber MBE
YouTube video by The Retro Collective
www.youtube.com
November 12, 2025 at 8:19 AM
diodesign.org
And on to another week. Grateful for everything, especially these views from the weekend.
View of the Golden Gate Bridge in San Francisco on a clear sunny day, from the Baker Beach trail View of the Pacific Ocean, looking south from the Baker Beach trail in San Francisco on a sunny day as the sun starts to set
September 22, 2025 at 4:10 AM
diodesign.org
If you want to get started writing your own kernel for 32-bit RISC-V from scratch, here's how seiya.me did it in 1,000 lines of cleanly written C. There's documentation to go with it. Pretty cool IMHO!

github.com/nuta/operati...
OpenSBI v1.5.1 ____ _____ ____ _____ / __ \ / ____| _ \_ _| | | | |_ __ ___ _ __ | (___ | |_) || | | | | | '_ \ / _ \ '_ \ \___ \| _ < | | | |__| | |_) | __/ | | |____) | |_) || |_ \____/| .__/ \___|_| |_|_____/|____/_____| | | |_| Platform Name : riscv-virtio,qemu Platform Features : medeleg Platform HART Count : 1 Platform IPI Device : aclint-mswi Platform Timer Device : aclint-mtimer @ 10000000Hz Platform Console Device : uart8250 Platform HSM Device : --- Platform PMU Device : --- Platform Reboot Device : syscon-reboot Platform Shutdown Device : syscon-poweroff Platform Suspend Device : --- Platform CPPC Device : --- Firmware Base : 0x80000000 Firmware Size : 319 KB Firmware RW Offset : 0x40000 Firmware RW Size : 63 KB Firmware Heap Offset : 0x47000 Firmware Heap Size : 35 KB (total), 2 KB (reserved), 10 KB (used), 22 KB (free) Firmware Scratch Size : 4096 B (total), 244 B (used), 3852 B (free) Runtime SBI Version : 2.0 Boot HART ID : 0 Boot HART Domain : root Boot HART Priv Version : v1.12 Boot HART Base ISA : rv32imafdch Boot HART ISA Extensions : sstc,zicntr,zihpm,zicboz,zicbom,sdtrig,svadu Boot HART PMP Count : 16 Boot HART PMP Granularity : 2 bits Boot HART PMP Address Bits: 32 Boot HART MHPM Info : 16 (0x0007fff8) Boot HART Debug Triggers : 2 triggers Boot HART MIDELEG : 0x00001666 Boot HART MEDELEG : 0x00f0b509 [ snipped ] virtio-blk: capacity is 0 bytes file: hello.txt, size=83 file: meow.txt, size=6 > hello Hello world from shell!
September 22, 2025 at 2:49 AM
diodesign.org
A 1956 general-purpose digital computer, the Bendix G-15, plus an algorithm from the modern-day CERN ATLAS experiment equals... this:

www.youtube.com/watch?v=2y0D...

What takes under a microsecond on hardware today takes about 15 minutes on this vacuum-tube machine
CERN Topoclustering on the Bendix G-15!
YouTube video by Usagi Electric
www.youtube.com
August 25, 2025 at 5:17 AM
diodesign.org
Wonderfully detailed per-frame performance analysis of NES Metroid, and why it lags at certain points. It's super interesting to see the software engineering decisions taken back in the day.

As always, a great video by @displacedgamers.bsky.social IMO

www.youtube.com/watch?v=3G6v...
Still from Displaced Gamers' https://www.youtube.com/watch?v=3G6vkRz-_0I video that depicts a frame from the NES game Metroid overlaid with statistics and a list of subroutines called in the game loop. The statistics show the percentage of time per frame spent in each subroutine as well as total frame counts and rendered frame counts.
August 17, 2025 at 7:43 AM
Reposted by Chris Williams
steveklabnik.com
#ziglang ’s Lovely Syntax

matklad.github.io/2025/08/09/z...
Zig's Lovely Syntax
It's a bit of a silly post, because syntax is the least interesting detail about the language, but, still, I can't stop thinking how Zig gets this detail just right for the class of curly-braced langu...
matklad.github.io
August 10, 2025 at 4:11 PM
diodesign.org
I like alternative languages and architectures to see how syntax, structure, and other implementation details can be done differently.

There's not only ziglang.org which I think is cool, but also SystemVerilog alternative Veryl: github.com/veryl-lang/v... Yet another side project coming on.
GitHub - veryl-lang/veryl: Veryl: A Modern Hardware Description Language
Veryl: A Modern Hardware Description Language. Contribute to veryl-lang/veryl development by creating an account on GitHub.
github.com
July 19, 2025 at 5:39 PM
diodesign.org
This looks like a super meeting for those interested in Acorn, Arm, and RISC OS history
rougol.bsky.social RISC OS London @rougol.bsky.social · Jun 14
Some things that will be covered:
- What it was like in the early days of Acorn
- DFS and ADFS dev
- Tube co-pro bugs
- Project A, the ARM CPU
- How to test a chip that doesn’t exist yet!
- Many emulators
- First ARM silicon
- Shifting issues
- Plus FPU, RISCiX, and time wasted on ARX
rougol.bsky.social RISC OS London @rougol.bsky.social · Jun 10
At next Monday's (16th June) ROUGOL meeting Hugo Tyson will be joining us in the pub to talk about everything(ish) he did at Acorn rougol.jellybaby.net/meetings/ind...
June 16, 2025 at 3:39 PM
diodesign.org
FYI: Gerph has been re-implementing RISC OS – which started as Arm's very first OS – in Python, allowing 32 and 64-bit apps and other software to build and run on non-Arm systems. Amazing work

More on RISC OS Pyromaniac: pyromaniac.riscos.online
Latest here: www.riscosopen.org/forum/forums...
RISC OS 7 post-boot showing its initialization messages and then a list of available OS-level modules. Taken from http://shell.riscos.online/ Acorn's Maestro music editing and playback application running on Gerph's Pyromaniac RISC OS in the desktop RISC OS Pyromaniac desktop running full-screen on macOS Source: https://pyromaniac.riscos.online/examples.html#talk2022
June 7, 2025 at 5:10 PM
diodesign.org
Recently enjoyed seeing and listening to quite a mix of live music in the Bay Area, from Kylie and Underworld in San Francisco to Kraftwerk in Berkeley. All pretty stunning, and all great sounds I grew up with that I finally got to experience in person.
Kylie Minogue on stage at the Chase Center in San Francisco with a disco ball lighting up the whole scene. The band Underworld on stage at the Warfield in San Francisco, with a lot of red lighting and dry ice. Kraftwerk on stage at the Berkeley Greek Theatre, with Computerworld showing on screen.
May 29, 2025 at 5:34 AM
diodesign.org
Watching some old EEng videos, because why not, and find a 50-min 1988 video from Intel about the design and challenges of its 386 CPU

And look who shows up, in his late 20s, talking about mixing automation and hand drawing of transistor layout on silicon and more

www.youtube.com/watch?v=LQcL...
Still frame from the linked YouTube video of now ex-Intel CEO Pat Gelsinger, in 1988, showing his name and job title: Microprocessor Project Manager
December 30, 2024 at 5:05 AM
diodesign.org
More adventures in #Zig and bare-metal RISC-V! Heap allocator is done, with merging of adjacent free blocks. A little more atomics for multi-CPU/thread support. And lots learned about the language.

github.com/diodesign/di...

And now onto device tree parsing and generation...
Screenshot showing some of the heap allocation code and diosix running in a terminal showing debug output to the serial port: qemu-system-riscv64 -nographic -machine virt -smp 4 -m 2G -bios none -kernel zig-out/bin/vmdiosix Visit https://diosix.org for usage, copyright, and distribution. Version 0.3.0-zig (95dba5e) Tue Dec 24 11:01:17 AM PST 2024 riscv64 Device tree at 0xbfe00000 CPU core ID 1 waiting for work... CPU core ID 3 waiting for work... CPU core ID 2 waiting for work... CPU core ID 0 waiting for work... QEMU: Terminated
December 24, 2024 at 7:17 PM
diodesign.org
It's the holiday season, I've got some time off work, and so I'm gonna finally dive into Zig and RISC-V

ziglang.org
riscv.org/developers/

I've got bare-metal execution in Qemu, writing hello world out to the serial port. Let's bring up more of an environment and then try this on real hardware...
Screenshot of the following zig code in a purple-themed Visual Studio Code window: export fn main() void { const uart: *volatile u8 = @ptrFromInt(0x10000000); const hello: []const u8 = "Hello world!!\n\n"; for (hello) |c| { uart.* = c; } while (true) {} } And the execution of that code in a terminal below: % qemu-system-riscv64 -nographic -machine virt -smp 1 -m 1G -bios none -kernel zig-out/bin/vmdiosix Hello world!!
December 18, 2024 at 1:58 AM
diodesign.org
RISC-V CEO Calista Redmond resigns -- I have high hopes for RV, as I'm all for market competition. Calista had a tough job driving through a new ISA and IMHO did great

riscv.org/riscv-news/2...
RISC-V CEO Calista Redmond resigns after 5+ years of progress – RISC-V International
riscv.org
December 13, 2024 at 3:59 AM
diodesign.org
Been a fan of Orbital since I was a teenager. Never got the chance to see them live in the UK. Super happy to have caught them on tour in San Francisco this weekend.

Amazing night of progressive-house-techno-whatever you want to call their unique sound :)
View from the crowd looking toward the stage where Orbital were playing live at the Midway in San Francisco.
November 18, 2024 at 4:10 AM
Reposted by Chris Williams
kelseyhightower.com
The tech migration from Twitter continues. One by one.
quinnypig.com Corey Quinn @quinnypig.com · Nov 15
I'm making a similar shift now. It's time.
kelseyhightower.com Kelsey Hightower @kelseyhightower.com · Oct 20
Today was my last post on Twitter. I'll be using this account going forward while I contemplate the value of social media in my daily life.
November 15, 2024 at 9:55 PM
Reposted by Chris Williams
theregister.com
OK, now that the stampede to BlueSky has died down for a moment, and systems are a bit more stable, let's try sharing this again - our starter pack. Thanks for joining us!

go.bsky.app/EsDR7M7
November 13, 2024 at 2:59 AM
diodesign.org
Debian has been a bedrock for me. Pretty much every dependable system I use has Debian at its core.

I can't imagine using any other OS

https://www.theregister.com/2023/08/17/debian_turns_30/
Debian turns 30 – and important to Linux world as ever
August 16 was an especially big day for this island of stability
www.theregister.com
August 18, 2023 at 4:22 AM
diodesign.org
I quite like the design of this, and that it's aimed at devs. Neat way to get secure P2P into apps. Written mostly in Rust, too
theregister.com The Register @theregister.com · Aug 12
Veilid was launched at DEF CON today

Tl;dr: ‘It’s like Tor and IPFS had sex and produced this thing’

It's code developers can add to their apps so that their software can communicate securely and privately via a P2P network

https://www.theregister.com/2023/08/12/veilid_privacy_data/
Cult of the Dead Cow unveils Veilid peer-to-peer project
‘It’s like Tor and IPFS had sex and produced this thing’
www.theregister.com
August 12, 2023 at 2:49 AM
Reposted by Chris Williams
theregister.com
First Zenbleed, now Downfall. We've got a fab overview of these two data-leaking CPU bugs in AMD and Intel processors, both found by Googlers, here:

https://www.theregister.com/2023/08/09/google_intel_downfall/
Downfall data-leak vulnerability found in Intel processors
It is with a heavy heart that we must announce that the boffins are at it again
www.theregister.com
August 9, 2023 at 7:42 PM