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Next-gen chips will be powered from below
- Zenst 5y agoQuestion I have is how much heat is generated by that power layer and as it is copper, shifting that behind the silicon - would we not see more thermal mass shifted to the backend of the CPU and with a focus upon the top of the cpu for cooling solutions - how would that pan out? Would we also need some heat-sink upon the base of the CPU. Would we see extra heat shifted thru the silicon layer with this process? One aspect that I've pondered that would save power would be having the memory closer to the CPU and all that usable real-estate for slots upon the reverse of the motherboard. Sure you would be looking at new case designs in a way or existing ones with new design considerations upon the mounting plate to have gaps to accommodate sockets upon the reverse of the motherboard PCB. That without having to compete with the CPU airspace for cooling and in effect using the motherboard to zone things, could work out well.
- baybal2 5y agoMost high end chips with high TDPs are already packaged upside down. You CPU, or 9 out of 10 recent phone/tablet SoCs are all upside down chips. https://en.m.wikipedia.org/wiki/Flip_chip https://en.m.wikipedia.org/wiki/Flip_chip So, it's actually going to be an improvement from the thermals side, especially with TSVs carrying heat from the other side to the heatsink.
- hinkley 5y agoThe power layer is going to leak less power to heat than the other layers, correct? So the power rails will work as heat spreaders, if not particularly great ones.
- ajaimk 5y agoArticle says this: 10% loss budget in Front side power delivery with a 7x improvement in the future => <2% of heat on bottom.
- formerly_proven 5y agoNot really, no. Pretty much all LSI chips (and even a lot of power / analog stuff these days) is flip chip, i.e. mounted metal-layer down (if you see a BGA or waferscale package, all of these are flip-chip). So the stackup looks like this (roughly to scale): Heatspreader TIM Silicon Silicon Silicon Silicon Silicon Silicon Silicon Silicon Silicon Active layer Metal layers Metal layers Passivation Solder bumps and glue Solder bumps and glue Solder bumps and glue Solder bumps and glue Substrate/interposer/PCB What this article proposes is to put metal layers on BOTH sides of the active layer, so you get more metal closer to it. That's what they mean by "powered from below". If you look at a chip today, they're all "powered from below" in the sense that the metal layers are "below" the active layer and power (and all signals) are fed in from "below" through the interposer.
- Zenst 5y agoThank you and appreciate the layer listing - most elegantly done.
- nimish 5y agoThis has already happened with cerebras and tesla dojo at least.
- blendergeek 5y agoSource? I'd be interested in reading more about that.
- nimish 5y agohttps://fuse.wikichip.org/news/3010/a-look-at-cerebras-wafer-scale-engine-half-square-foot-silicon-chip/2/ https://fuse.wikichip.org/news/3010/a-look-at-cerebras-wafer... Power fed vertically. Not sure it's BPR specifically, but they do mention ~50% efficiency improvement in the PDN so it's comparable.
- rcMgD2BwE72F 5y agohttps://www.youtube.com/watch?v=QurtwJdb5Ew&t=229 https://www.youtube.com/watch?v=QurtwJdb5Ew&t=229
- jagger27 5y ago> it's consuming 200 W to provide its transistors with about 1 to 2 volts, which means the chip is drawing 100 to 200 amperes of current from the voltage regulators that supply it. Your typical refrigerator draws only 6 A. High-end mobile phones can draw a tenth as much power as data-center SoCs, but even so that's still about 10–20 A of current. That's up to three refrigerators, in your pocket! This feels out of place coming from IEEE.
- amelius 5y agoI don't know. I bet half of IEEE only worries about data/signal processing in their dayjobs and never thinks about power distribution. Such a comparison immediately makes clear what the problem is.
- rzwitserloot 5y agoEspecially considering the fact that this is harping on about Ampere. Which is _not_ the number to be looking at here; that'd be watts. That fridge is chugging down 6A at 110 or 220V (assuming it's a new fridge, unless its absolutely gigantic or incredulously inefficient, sounds like that'd be a 110V model) - not at 1 to 2 volts. If someone can build a fridge that is so efficient, it can make do with 6A @ 2V, dang. Where can I buy me one of those? That's 12W total, I can power one of these for a full hour with 4 AA batteries.
- wheels 5y agoI thought the same initially, and do think the analogy is bad, but a few seconds later I wondered if the point that they were making was that the interconnects carry the same amperage: the required gauge for a connector (i.e. wire) is determined by amps, not watts. As a result you can send more power down smaller cables at higher voltages.
- willis936 5y agoYeah the ohmic losses in the power delivery networks are the killer and the topic of this article.
- baybal2 5y ago> they typically consume only about 200 to 400 watts per square centimeter. That's quite a gross inaccuracy coming from the ARM researchers. Most chips barely get above 100W/cm², and it's a very hard limit.
- addaon 5y agoFor comparison, the surface of the sun is about a seventh of a watt per square centimeter.
- philipkglass 5y agoThe sun emits about 63 megawatts per square meter (6300 watts/cm^2): https://www.acs.org/content/acs/en/climatescience/energybalance/energyfromsun.html https://www.acs.org/content/acs/en/climatescience/energybala... Were you perhaps thinking of the intensity of sunlight reaching the top of Earth's atmosphere?
- addaon 5y agoHm, I wish I knew how I did my math originally... you seem to be quite right.
- ChrisMarshallNY 5y ago> That's up to three refrigerators, in your pocket! Bit misleading, there. A != W
- marcosdumay 5y agoCurrent is the one number you look when talking about power transmission.
- ChrisMarshallNY 5y ago...aother one, being Volts (which brings us back to...W). Also AC/DC, Waveshape, RMS/Peak, Frequency, etc... W is watt ("Watt" -geddit?) cooks your junk, if the phone has a heat issue. Used to be an EE, back in the Dawn Times...
- marcosdumay 5y agoVoltage is a completely different issue, that has only indirect impact on "how big will this thing be?", at least until you start measuring it by the hundreds. Of course, all of those are relevant, but the one number that sizes the thing is current.
- hliyan 5y agoThe metal-filled trenches in the silicon need to survive high temperatures, so according to the article copper is out of the question. They "experimented with ruthenium and tungsten" but it's not clear whether they actually built something or whether it was all simulation. Either way, this is likely to make the chips more expensive.
- unnouinceput 5y agoIt's a simulation, they don't even have a prototype yet. Quote: "Simulation studies are a great start, and they show the CPU-design-level potential of back-side PDNs with BPR. But there is a long road ahead to bring these technologies to high-volume manufacturing. There are still significant materials and manufacturing challenges that need to be solved. "
- brennanpeterson 5y agoI doubt this is true. Mike Mayberry (Intel) softly announced buried power rail last year, as a 'within 5 years' tech. That suggests it has been prototyped, since from final tests to HVM is at least 2 years. Maybe not great. Within 10 means an idea with simulation. Within 5 means prototyped. Interesting means never. Or that, at least, is my decoder ring.
- nine_k 5y agoFor one thing, if a tungsten wire is an order of magnitude better conductor than a layer of copper you normally would use, the situation with power delivery is indeed dire. Tungsten's specific resistivity is about 4 times as high as copper's.
- tus89 5y agoI sure am sick of those ICs with pins sticking out of the top. Progress at last!
- phendrenad2 5y agoUnrelated, but I wonder if inductive charging will eventually make it's way into chips. The chip could be powered by an antenna on the board below.
- samename 5y agoOff topic: why do websites have a button to “keep reading” for showing the whole post? It’s already loaded, why not display the whole thing?
- shakna 5y agoTwo interrelated things. First, metrics. When you click the button, they get a signal that someone has been reading the page. Secondly, there are a lot of JS APIs that require human interaction before you're allowed to use them, for privacy reasons. By clicking a button, those are "unlocked" and they can send all your privacy-obliterating data back along with their metrics.
- doublepg23 5y agohow did we get to this place where dark patterns are this common.
- nine_k 5y agoHave you paid to read the article? That's how :( The publishers want money, just to pay their bills.
- KirillPanov 5y agoIs there a list of these JS APIs somewhere? Or a specific search term for this interaction requirement phenomenon? I tried the obvious searches, but got lots of false positives in the results. I am asking as a non-web developer who cannot resist rubbernecking at the incredible dumpster-fire-on-a-trainwreck that is web privacy.
- shakna 5y agoI don't believe there's an easy list anywhere - mostly because which APIs require interaction, and which don't, is not standardised. It changes radically between browsers, and browser versions, even before you get to user settings in those browsers that can change it further.
- sandworm101 5y agoI wonder if there is anything to come from wireless power delivery inside chips. If the entire chip was bathed in constant RF, then bits of the chip could pick up power when and where needed via tiny antennas harvesting the RF field. It would require some very tricky control of wavelengths but might eliminate many wires. Lasers might also offer interesting possibilities for delivering power without wires. How small can we make a photovoltaic panel?
- hinkley 5y agoIf that were possible, wouldn’t capacitive coupling be simpler and achieve a similar goal?
- KirillPanov 5y agoIf you try sending RF power to LSI-scale antennas, the LSI-scale signal wires near them will be antennas too.
- ruslan 5y agoSince antenna efficiency directly depends on it's size-to-wavelength (resonance), to get them working we have to deliver power at extremely high frequencies, like 3e16 Hz I quess, which is not feasible.