
Seeking Big A.I. Advances, a Startup Turns to a Huge Computer Chip - druidsbane
https://fortune.com/2019/08/19/ai-artificial-intelligence-cerebras-wafer-scale-chip/
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nmstoker
[edit] They did mention the error/bad core handling briefly, as Druidsbane
correctly points out [/edit]

Obviously not much specific detail at this stage, but it strikes me as odd
that there's no points from Cerebras that seem to address the obvious concern
with fabrication errors - I'd always understood that by having many small
chips that mitigated costs, because one single chip could be toast but you'd
still have a substantial number of unaffected ones to use.

Unless they've got some special solution up their sleeves, it seems like one
error would knock out the whole chip.

Also, by needing it to be square, won't they fail to utilise the sections
between the edge of the square and the edge of the wafer's circular edge?

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druidsbane
The article mentions that they are building extra circuitry to circumvent any
bad cores. Not much detail but at least they have addressed this.

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nmstoker
Sorry you're completely right, I must've missed that whole paragraph.

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amatus
I'd love the see the details of how they remove heat from that monster chip.

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cr0sh
For something this large, it likely isn't "encapsulated" like a normal chip.
I'd almost expect it to be left more or less "bare", mounted to some kind of
very stiff PCB-like material (which is probably bonded to aluminum or
something). Then wire bonds from the "chip" to the PCB.

The whole thing is probably then immersed into some kind of non-conducting
fluid (mineral oil or fluorinert would be my two first guesses), probably
vertically to take advantage of thermal circulation. Mechanical circulation of
the coolant would likely be very gentle so-as not to disturb the wire bonds,
unless they have something special to keep them in place (maybe the bonds and
edge of the chip are encapsulated leaving the center bare?).

All of this is just guesses from somebody not an expert or even ever touched
stuff like this, just based on what little I know about how normal sized chips
are packaged.

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auslander
Ryzen Zen2 7nm has 3.9B transistors on 80mm2. Thats 50M/mm2.

1.2 Trillion on 8.5" squared gives 26M/mm2. Impressive. But would take cryo
lab to cool, i think.

