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Comment by ufocia | Hacker News Reader

I like the video, but this is hardly groundbreaking. You send out two or more messengers hoping at least one of them will get there on time.

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Yeah. These are literally just mainframe techniques from yesteryear.

Almost everything "new" was invented by IBM it seems like. And it goes by a completely different name there. It's still nice to rediscover what they knew.

As another poster said, the impressive part here is the work on lining up all the technical features to implement this simple concept. Though I'm the end Laurie realized that essentially brute force worked well.

One thing that I'd think about improving is the boundary search. It seems to me at mere first glance that binary search would usually be much faster. Also, knowing what architecture is used, e.g. channel width, could further optimize the search.

The clever part is figuring out what RAM is controlled by which controllers.

everyone says this but no one says why it was clever. i find her videos have cool results but i cant have patience for them usually because its recycled old stuff (can be cool but its not ground breaking).

there is a ton of info you can pull from: smbios, acpi, msrs, cpuid etc. etc. about cpu/ram topology and connecticity, latencies etc etc.

isnt the info on what controllers/ram relationships exists somewhere in there provided by firmware or platform?

i can hardly imagine it is not just plainly in there with the plethtora info in there...

theres srat/slit/hmat etc. in acpi, then theres MSRs with info (amd expose more than intel ofc, as always) and then there is registers on memory controller itself as well as socket to socket interconnects from upi links..

its just a lot of reading and finding bits here n there. LLms are actually really good at pulling all sorts of stuff from various 6-10k page documents if u are too lazy to dig yourself -_-

The exact mapping between RAM addresses and memory controllers is intentionally abstracted by the memory subsystem with many abstraction layers between you and the physical RAM locations. Because documentation is sometimes incomplete or proprietary, security researchers often have to write software that probes memory and times the access speeds to reverse-engineer the exact interleaving functions of a specific CPU. in the video she says that ARM CPUs have the least data about this and she had to rely entirely on statistical methods.

It's very funny that you're giving a RTFM response to a video you admit you didn't watch.

WTFV

I have to say that using drawbridges and differently colored rail pieces to explain it was very clever.

and dropbox was just rsync

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