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matja

1,184 karma · joined December 29, 2018

https://github.com/matja
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matja··on Branch Privilege Injection: Exploiting branch predictor race conditions
For reads across different VMs on the same CPU, theoretically TME-MK could mitigate the usefulness of the memory reads by having each VM access memory using a different memory encryption key, but I don't know of any hypervisors that implement this.

AMD has had SEV support in QEMU for a long time, which some cloud hosting providers use already, that would mitigate any such issue if it occurred on AMD EPYC processors.

matja··on Branch Privilege Injection: Exploiting branch predictor race conditions
The Linux kernel has had microcode loading support (`CONFIG_MICROCODE` / `CONFIG_MICROCODE_INTEL`) but many years, but it does require that Intel release the microcode files necessary for distribution maintainers to update the packages, then it should be included in a system update.
matja··on I hacked a dating app (and how not to treat a security researcher)
Eliminate your database costs with this one easy trick!
matja··on Vision Now Available in Llama.cpp
For every image I try, I get the same response:

> This image shows a diverse group of people in various poses, including a man wearing a hat, a woman in a wheelchair, a child with a large head, a man in a suit, and a woman in a hat.

No, none of these things are in the images.

I don't even know how to begin debugging that.

matja··on 21 GB/s CSV Parsing Using SIMD on AMD 9950X
Kind of, there isn't a 1:1 mapping of protobuf wire types to schema types, so you need to package the protobuf schema with the data and compile it to parse the data, or decide on the schema before-hand. So now you need to decide on a file format to bundle the schema and the data.
matja··on 21 GB/s CSV Parsing Using SIMD on AMD 9950X
4 generations?

5950x is Zen 3

9950x is Zen 5

matja··on Find the Odd Disk
18/20. I struggled most with the blue ones, but it was actually a purple and a green one that I got wrong - which wasn't what I was expecting! ASUS sRGB OLED at 50% brightness.
matja··on The mistakes and missed opportunities in the design of IPv6
> was a stupidly complex beast compared to IPv4

How are you measuring complexity?

IPv4 started simple, but had a lot of extensions (literally header "options") to fix and mitigate various issues and underspecified behaviour.

IPv6 started more complex, but had a lot of those shortcomings addressed from decades of experience in the real world.

In the Linux kernel, IPv6 is actually implemented with fewer lines of code than IPv4 (as of 6.12.19, IPv4 = 82kloc, IPv6 = 58kloc).

matja··on Send Data with Sound
There's also http://www.whence.com/minimodem/ which implements some standard methods:

> standard FSK protocols such as Bell103, Bell202, RTTY, TTY/TDD, NOAA SAME, and Caller-ID

matja··on Microsoft unveils Majorana 1 quantum processor
When a company that makes quantum computers is on this page: https://en.wikipedia.org/wiki/RSA_Factoring_Challenge
matja··on How to Run DeepSeek R1 671B Locally on a $2000 EPYC Server
How would it use 1kW? Socket SP3 tops at 280W and the system in the article has a 850W PSU so I'm not sure what I'm missing.
matja··on Google Pixel 4a old firmware is gone, trapping users on the buggy battery update
Are these not the old images? : https://developers.google.com/android/images#bramble
matja··on Cracking a 512-bit DKIM key for less than $8 in the cloud
Was it a key affected by CVE-2008-0166 ? :)
matja··on Cracking a 512-bit DKIM key for less than $8 in the cloud
I don't think this rationale is correct. DKIM doesn't authenticate a user, since the user doesn't the private key - DKIM authenticates that the MTA knows the private key on behalf of the domain owner, which isn't necessarily the users using that domain to send email.

What's more dangerous is that a jury wouldn't know the difference.

matja··on Nvidia announces next-gen RTX 5090 and RTX 5080 GPUs
The integrator decides the form factor, not NVIDIA, and there were a few 2-slot 3080's with blower coolers. Technically water-cooled 40xx's can be 2-slot also but that's cheating.
matja··on All clocks are 30 seconds late
The same technique is how computer RTCs are set/read, but to sub-second precision instead of minute precision, because the most common register standard allows only storing whole seconds but they keep relatively accurate time.
matja··on The saga of the color brown in the early years of the PC (2023)
TheRasteri on YouTube made a video on how CGA works at the hardware level, specifically the brown detection, and how to make a CGA to EGA converter: https://youtu.be/vwKA1z8tg1g?t=184
matja··on Just: Just a Command Runner
FYI to some people trivializing self-harm in a technical discussion is rather tasteless.
matja··on Contradictions in photography advice
> RAW vs JPG

Most cameras have an option to save both the raw (which depends on the camera make, probably .dng/.cr2/.nef) and also a JPEG using automatic white-balance and exposure options, so you can have the best of both worlds of a quick workflow (using just the JPEGs) or tweaking exposure/balance/tone in 12/14 bpp.

matja··on Hynix launches 321-layer NAND
Nothing - just marketing. It's their 2nd gen Periphery Under Cell (PUC) device.
matja··on SQLite does not do checksums
How do you know you never had corruption?
matja··on M4 MacBook Pro
Especially because pixel count is a meaningless metric by itself. 12MP is the same as a Nikon D3, which if it could replicate the results of I would be happy with!
matja··on Hack GPON – how to access, change and edit fibre ONTs
Does your ISP require you to register the MAC address of the HFC interface of your spare modem?
matja··on Show HN: Hosting my website using my C web server
Lack of IP(v4) addresses. HTTP/1.0 sends no Host header, so cannot implement name-based virtual hosts. HTTP/1.1 does.
matja··on Is my vision that bad? No, it's just a bug in Apple's Calculator
If only Apple used ECC RAM, then that would be easy to confirm.
matja··on HDMI Forum rejects AMD's HDMI 2.1 open-source driver
My HDMI cables work at 4k 120Hz with the same monitor with an NVidia card using closed-source drivers, not with AMD open-source drivers, because of the issue in the article.
matja··on HDMI Forum rejects AMD's HDMI 2.1 open-source driver
> Most people don't have hardware that requires HDMI 2.1 in order to get full use out of them, and of those who do, not all of them use Linux and/or care about open source drivers.

Arguably true, but I think that is changing all the time while there is a push towards open-source drivers regardless of the average user knowing/caring what that is, along with resolutions and refresh rates increasing.

I was affected by HDMI Forum's decision by buying an off-the-shelf 4K 120Hz monitor which refused to work at that resolution/refresh rate on an HDMI cable.

I was not expecting an arbitrary decision affecting software to be the cause instead of a hardware problem - which took me a while to figure out.

Now I know if I want to use my hardware to the full capacity, I need DisplayPort in future.

matja··on The journey of an internet packet: Exploring networks with traceroute
Windows tracert uses ICMP

Source: https://support.microsoft.com/en-gb/topic/how-to-use-tracert...

> The TRACERT diagnostic utility determines the route to a destination by sending Internet Control Message Protocol (ICMP) echo packets to the destination

matja··on DUNE scientists observe first neutrinos with prototype detector at Fermilab
They preserve the spin quantity in particle interactions. E.g. in beta decay a spin-neutral atom has a neutron that decays into a proton and an electron. Neutrons, protons and electrons have spin 1/2, so an extra 1/2 spin came about. An anti-neutrino has spin -1/2 which is emitted to balance the spin quantity.
matja··on A 1.3B-light-year-across ring of galaxies has confounded astronomers
Similar to the plot of https://en.wikipedia.org/wiki/Ring_(Baxter_novel)
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