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Matt Godbolt

@matt.godbolt.org

Sometime verb, real person, lover of 8-bit computers, husband & father, trying to be a kind person. #blacklivesmatter; trans rights are human rights. he/him

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Latest posts by Matt Godbolt @matt.godbolt.org

Got it. Ok I'm that case that's 100% my fault as ^D is burned into me as duplicate line so I abused my power to hack it in...sorry! If nobody else uses it I should probably remove it...

05.03.2026 13:02 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

^D is my fault lol sorry :). It's a thing i use all the time...

But it's more like you'd like customisable key bindings in CE? That's probably a bit too much for us to do, the configuration UI is a lot of work; though if someone wants to send a PR we'd take it :)

05.03.2026 11:56 πŸ‘ 2 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

To work in what sense?! We use Monaco which is as best I know the same editor as vscode?

05.03.2026 04:51 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Issue 8536

04.03.2026 18:56 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Well...oops...that's a dumb omission! Filing! :)

04.03.2026 18:52 πŸ‘ 4 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Yes; configurable in the options :)

04.03.2026 18:32 πŸ‘ 6 πŸ” 0 πŸ’¬ 2 πŸ“Œ 0
Screenshot telling me I can get 6 months of Max! Yay!

Screenshot telling me I can get 6 months of Max! Yay!

Screenshot of what happens after I accept the Max 20x. I am already on 20x so can't "accept" this, only "downgrade to 5x more usage" :(

Screenshot of what happens after I accept the Max 20x. I am already on 20x so can't "accept" this, only "downgrade to 5x more usage" :(

I really appreciate the 6mo free, @anthropic.com ! Yay but - I'm already on 20x and I can't accept it... - please help :)

03.03.2026 22:39 πŸ‘ 5 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
RISC OS User Group Of London | Meetings

At our next meeting on Monday 16th March come chat with @matt.godbolt.org in the pub (or on Zoom if you must) about JSbeeb, Compiler Explorer, and more! Free entry, but you have to buy your own drinks πŸ˜›
rougol.jellybaby.net/meetings/ind...

03.03.2026 14:40 πŸ‘ 13 πŸ” 7 πŸ’¬ 0 πŸ“Œ 0

I had to

03.03.2026 01:37 πŸ‘ 2756 πŸ” 758 πŸ’¬ 45 πŸ“Œ 4

Sounds about right :-)

28.02.2026 00:19 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

It's certainly a fun thing to debug when you get a very performance issue!

28.02.2026 00:01 πŸ‘ 2 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Pentium 4 Trace Cache is so back! Except yeah in a different way. The trace cache was the right idea, and when it worked it worked really well. But when it didn't the perf holes were pretty terrible. So instead we have something slightly less full-on, but it recovers more gracefully.

27.02.2026 23:56 πŸ‘ 9 πŸ” 1 πŸ’¬ 2 πŸ“Œ 0
Matt Godbolt: Advanced Skylake Deep Dive
Matt Godbolt: Advanced Skylake Deep Dive YouTube video by Jane Street

For folks who was a very niche, Intel Skylake-focused video on some of this stuff (although not so much the regular RAM cache part) I gave a talk a few months back on the subject: youtu.be/BVVNtG5dgks
It's such a fascinating topic, and changes quite rapidly, but the general ideas are the same still.

27.02.2026 22:25 πŸ‘ 27 πŸ” 1 πŸ’¬ 1 πŸ“Œ 0
Post image Post image

Most programmers are taught that L1 is the β€œtop level” cache on x86.


It’s not quite true anymore!


Intel calls it the Decoded Stream Buffer (DSB), AMD the OpCache.

Only enough room for ~4,000 micro-ops, but there are interesting ways to take advantage of it.

27.02.2026 19:42 πŸ‘ 150 πŸ” 18 πŸ’¬ 4 πŸ“Œ 1
Cyclic Redundancy Check (CRC) - Computerphile
Cyclic Redundancy Check (CRC) - Computerphile YouTube video by Computerphile

youtu.be/_x0vbnUKYSU

This time with an embedded link

25.02.2026 17:22 πŸ‘ 14 πŸ” 2 πŸ’¬ 0 πŸ“Œ 0

Thank you! Honestly the hard work is done by @seanski44.bsky.social in trying to edit something coherent from my ramblings!

25.02.2026 17:16 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

How do we know the random series of bits we just sent down your cable didn't get corrupted on the way? With CRCs! But what are these mysteries checks...I try to explain on today's @computerphile.bsky.social !https://youtu.be/_x0vbnUKYSU

25.02.2026 16:13 πŸ‘ 19 πŸ” 1 πŸ’¬ 2 πŸ“Œ 0

Address generation interlock?!

22.02.2026 01:02 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Actually I don't! Maybe I should make one myself :)

21.02.2026 15:44 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Maybe both hahaha :)

20.02.2026 15:44 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Omg a whole part of my brain has lain dormant for 30+ years until being reminded of this! Thank you!

20.02.2026 04:43 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
Preview
Index of all deep dive articles - The Sentinel on the BBC Micro Index of all deep dive articles about The Sentinel

I'm releasing over 50 deep dives into The Sentinel, Geoff Crammond's epic #BBCMicro game.

Batch #1 is now ready: 6 new articles about memory maps, program flow and interrupts, all at thesentinel.bbcelite.com/deep_dives

Batch #2 (maths!) coming soon.

Enjoy!

#retrocomputing #retrogaming #c64 #8bit

19.02.2026 16:28 πŸ‘ 56 πŸ” 20 πŸ’¬ 1 πŸ“Œ 1
Post image

Fellow nerds! πŸ€“ Want to help me play test my new Programming Puzzles Game website? programmingpuzzles.fun It's the companion site to my Programming Puzzles for Everyone book.

Have fun and report any issues.

19.02.2026 20:30 πŸ‘ 11 πŸ” 4 πŸ’¬ 0 πŸ“Œ 0
A Brief History of Bjarne Stroustrup, the Creator of C++
A Brief History of Bjarne Stroustrup, the Creator of C++ YouTube video by CultRepo

Uncommonly excited about this: www.youtube.com/watch?v=uDtv... - trailer for a biopic of the legend himself, Bjarne Stroustrup!

19.02.2026 18:02 πŸ‘ 33 πŸ” 4 πŸ’¬ 0 πŸ“Œ 0
Learn C++ by Example β€’ Frances Buontempo & Matt Godbolt β€’ GOTO 2026
Learn C++ by Example β€’ Frances Buontempo & Matt Godbolt β€’ GOTO 2026 This interview was recorded for the GOTO Book Club. #GOTOcon #GOTObookclub http://gotopia.tech/bookclub Check out more here: https://gotopia.tech/episodes/426 Frances Buontempo - Consultant,…

.@matt.godbolt.org interviews @fbuontempo.bsky.social about "Learn C++ by Example," exploring practical teaching methods that make modern C++ features accessible through games and self-contained examples.

19.02.2026 13:01 πŸ‘ 8 πŸ” 4 πŸ’¬ 2 πŸ“Œ 1

Hahaha you're not wrong. I'm trying to be upbeat about new tech ideas without being too doomy. It's tough to try and stay in the middle :)

16.02.2026 21:46 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Super important in this world of LLMs that /may/ speed up code writing but may also have some important caveats!

16.02.2026 21:36 πŸ‘ 7 πŸ” 1 πŸ’¬ 1 πŸ“Œ 0
A die photo of the 8087 chip, with the main functional blocks labeled. The chip is a tan rectangle with complex patterns in dark brown. Many of the patterned regions are textured rectangles. One of the largest rectangles is the microcode ROM in the middle. The bottom half of the chip is the datapath, performing operations on floating-point numbers. The instruction decoding happens in the upper left. Around the edges of the chip, bond wires connect the chip to the 40 external pins, but the pins are not visible, just short segments of the bond wires.

A die photo of the 8087 chip, with the main functional blocks labeled. The chip is a tan rectangle with complex patterns in dark brown. Many of the patterned regions are textured rectangles. One of the largest rectangles is the microcode ROM in the middle. The bottom half of the chip is the datapath, performing operations on floating-point numbers. The instruction decoding happens in the upper left. Around the edges of the chip, bond wires connect the chip to the 40 external pins, but the pins are not visible, just short segments of the bond wires.

In 1980, Intel released the 8087 floating-point chip, making math much faster. I'm reverse-engineering this chip, 46 years later. Most of its instructions are implemented in microcode, but some are implemented in hardware. Let's look at the circuitry that decodes instructions and decides what to do.

14.02.2026 17:46 πŸ‘ 134 πŸ” 27 πŸ’¬ 2 πŸ“Œ 0
Preview
Two's Complement A Programming Podcast by Ben Rady and Matt Godbolt

New Two's Complement Episode: How Fast is Fast?

Ben interviews Matt with a deceptively simple question: make my program go fast. 44 minutes later, robot dogs are falling over, Grace Hopper's wire turns up, and Matt still hasn't gotten the job.

Listen at: twoscomplement.org#podcast/how-... :)

14.02.2026 22:50 πŸ‘ 21 πŸ” 3 πŸ’¬ 1 πŸ“Œ 0

now that Git 2.53 is out, the Git data model @omarieclaire.bsky.social and I wrote is on the official Git website! git-scm.com/docs/gitdata...

14.02.2026 13:47 πŸ‘ 243 πŸ” 36 πŸ’¬ 5 πŸ“Œ 3