Chris Williams
LightNews LightNews
banner
diodesign.org
Chris Williams
@diodesign.org
400 followers 210 following 46 posts
Work: https://docs.cloud.google.com/
Personal: https://diodesign.org/
Wear sunscreen.
Posts Replies Media Videos
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
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
diodesign.org
Also not quite Times Square, but Manchester Piccadilly Station in the UK was hard to miss
A large display in front of Manchester Piccadilly Station, England, shows a Windows blue-screen-of-death. Source: https://www.theregister.com/2016/08/29/bsods_at_scale_we_laugh_at_your_puny_five_storeys_heres_our_six_storey_fail/
August 10, 2025 at 9:47 AM
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
More adventures in bare-metal RISC-V Zig!

Now we've got spinlocking and serial debug output. Heap manager is next, and better exception debug output...
Screenshot showing the following terminal output: % zig-build % qemu-system-riscv64 -nographic -machine virt -smp 4 -m 2G -bios none -kernel zig-out/bin/vmdiosix xint: initialized xint: initialized xint: initialized xint: initialized hypervisor: CPU core ID 0 initialized hypervisor: CPU core ID 2 initialized hypervisor: CPU core ID 3 initialized hypervisor: CPU core ID 1 initialized
December 22, 2024 at 3:51 AM
diodesign.org
All right, after some distractions, we're in business with very basic interrupt and exception handling set up, ability to handle multiple CPU cores, foundations of per-CPU core stacks and heaps... Getting there!
Terminal showing the following text: % zig build % qemu-system-riscv64 -nographic -machine virt -smp 4 -m 2G -bios none -kernel zig-out/bin/vmdiosix Hello world from CPU core 0!!
December 18, 2024 at 12:20 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
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