Hacker News Reader

Comment by ramshanker | Hacker News Reader

Now that Cerebrus has proven it works, I would love to have an x86 / ARM / NVidia do this. And for best results, onboard one of the memory maker as well. Cerebrus seems to have underestimated memory requirement of LLM. So imagine, 16 H200 GPU along with single digit TB HBM memory stitched together on a single substrate wafer. It seems doable with correct technology.

Go for it China. You are in good track here.

View on HN

> 16 H200 GPU along with single digit TB HBM memory stitched together on a single substrate wafer

How on earth would you cool this?

Submersion cooling.

> How on earth would you cool this?

With liquid nitrogen. :-)

Seymour Cray solved this problem 40 years ago.

https://en.wikipedia.org/wiki/Cray-2#/media/File:Cray2.jpg

Bring back toxic waterfalls.

The issue with Fluorinert is not toxicity but a very high global warming potential.

Fluorinerts with very low global warming potentials have been invented since then.

> Although Fluorinert was intended to be inert, the Lawrence Livermore National Laboratory discovered that the liquid cooling system of their Cray-2 supercomputers decomposed during extended service, producing some highly toxic perfluoroisobutene.[5] Catalytic scrubbers were installed to remove this contaminant.

With that much constant heat, what chemical might be best/most practical I wonder.

https://en.m.wikipedia.org/wiki/Novec_649

https://en.m.wikipedia.org/wiki/Hydrofluoroether

15kW dissipated over that area isn't particularly challenging for an industrial water cooler - within reason, you can just keep cranking up the flow rate. What'd scare me is power delivery, because they've probably got >10,000 amps going to the die.

https://www.eetimes.com/powering-and-cooling-a-wafer-scale-d...

20K amps (!!!): https://vimeo.com/853557623

They use probably the fanciest piece of rubber (and metal) ever made to pass the power in frontside to the die.

Doing it with all that water needing to get everywhere is definitely a feat.

But the power itself isn't too bad. A square millimeter of wire can comfortably carry 20 amps, and you can scale that up pretty straightforwardly.

It looks like each of those 84 rectangles has to deal with 240 amps and has multiple square centimeters of contact with the voltage regulator card above it.

Direct-die vapor phase change cooler? That tends to be the fastest way to get heat out of a chip and to a big radiator. For industrial applications the need to run a big fan & a compressor are less problematic.

Reply on news.ycombinator.com