6 ms·

How do the thermals work out? The compute dies are already one heck of a hotplate, putting an entire layer of insulating silicon on top isn't going to improve t

How do the thermals work out? The compute dies are already one heck of a hotplate, putting an entire layer of insulating silicon on top isn't going to improve things?

deleted 5y ago
[deleted]
ido 5y ago
I recall years ago IBM had an experimental solution to that that involved liquid in between the layers to transport the heat (vague memory, I think they used an analogy to blood). A quick googling brings up this article, which I think may be the same thing: https://www.bbc.com/news/science-environment-24571219 https://www.bbc.com/news/science-environment-24571219
baybal2 5y ago
There are copper to copper connections in between dies.
bullen 5y ago
I'm pretty sure the longevity of chips manufactured now is going to be alot shorter than for older chips if you can run them at the same temperature! Both litography and the desperate search for infinite growth is going to hurt in the long run! I'm stacking up on 14nm Atom that I can passively cool at 42 degrees celcius full blast on 8 cores and 50nm (100.000 writes per bit) X25-E SSDs!
- nicolapcweek94 5y ago
  Got any specs on those Atoms? A passively cooled homelab build sounds pretty interesting...
  - timeinput 5y ago
    I have [1] which has a similar chip to what the parent described. Its a fun little computer. [1] https://www.newegg.com/supermicro-mbd-a1sri-2758f-o-intel-atom-c2758-2-4ghz-cpu-tdp-20w/p/N82E16813182855 https://www.newegg.com/supermicro-mbd-a1sri-2758f-o-intel-at...
  - bullen 5y ago
    It's the SuperMicro ones from 2017.
  - Marsymars 5y ago
    I'm planning on building a mini-ITX Atom-based system in the future either with a Jasper Lake (Pentium N6005) or a future Alder Lake-L CPU. ASRock makes mini-ITX motherboards with integrated Atom CPUs that are a bit more modern than Supermicro offerings.
    - bullen 5y ago
      I'm not waiting for an eventual tiny improvement in Gflops/watt... the SuperMicro boards are really industrial and the Atom line is being cancelled for a low wattage version of the consumer chips! I think these boards are the first and last to be able to run 100 years! Earlier models consume too much energy and subsequent will be too fragile/complex!
- bayindirh 5y ago
  > I'm pretty sure the longevity of chips manufactured now is going to be alot shorter than for older chips if you can run them at the same temperature! Don't be so sure. If it was going to be the case, we'd be changing CPUs like early Seagate disks at our datacenter. There's no measurable longevity loss in the CPUs that we observed in our data center. We use every system for ~7 years at full load.
  - bullen 5y ago
    What temp you got on those machines? Since you haven't tried the 7nm CPUs yet I guess we'll have to see? 7 years sounds really short to me, I'm planning on running my machines for 100 years!
    - bayindirh 5y ago
      Just looked to a bunch of Xeon Gold 6258Rs. They're running around ~70 degrees Celsius per die. The machine is under full load. I'm sure its fans are at full speed. That CPU's reported temperatures are 81 for high, 91 for critical (in degrees Celsius). We get new systems almost every year, so we have a rolling set consisting many systems. So, we have a cross section of systems to observe.
      - bullen 5y ago
        My rule of thumb is "if hardware is too hot for you to hold your finger on it indefinitely" it's too hot and it's going to break very soon! Temperature kills hardware, you need to bring those temperatures down, and the only way to do that is to lower the wattage! Atom is the perfect design, no crap and low power!
        bayindirh 5y ago
        > "if hardware is too hot for you to hold your finger on it indefinitely" it's too hot and it's going to break very soon! From my experience, that doesn't happen like that in enterprise hardware. Either wrong voltage (inside the system) or defective design causes premature death. If the server BMC says it's fine, it's fine. > Temperature kills hardware, you need to bring those temperatures down, and the only way to do that is to lower the wattage! High Performance Computing doesn't work like that, unfortunately :) > Atom is the perfect design, no crap and low power! I'm sure it has its own uses and can accomplish a lot, but in HPC, it won't cut it. I use small SBCs at home to do and try a lot of fun and useful stuff, but it has limits.
- grandinj 5y ago
  The wear on most electronics is more dependent on thermal __cycling__ than it is on temperature, assuming it is run without it's operating temperature regime.
- ryder9 5y ago
  [citation required], make claims based on data not on your feelings
IshKebab 5y ago
Silicon isn't that bad of a conductor, and given that it is very thin I'd guess it doesn't affect things too badly.
amelius 5y ago
Thermal resistance is linear in thickness, so if the Si on top is very thin, then perhaps it doesn't matter too much?
flumpcakes 5y ago
Silicon is a crystal, and like metals it conducts heat very well. Copper 400 W / m K Aluminium 230 W / m K Silicon 150 W / m K Iron/Steel 50 W / m K
- formerly_proven 5y ago
  These devices are often thermally constrained as it is, so the question how this (adding extra silicon on top of the existing die [1]) affects thermals is important. Also neither copper nor silicon are responsible for the "bulk" of the heat transfer - the goal is always to get to a heatpipe or vapor chamber near you as quickly as possible, because those deliver well above 10000 W/m*K. [1] Though Intel thinned their dies recently to improve thermal performance (CPUs are flip-chip, so the metal layers and active circuitry are facing the interposer). Some were concerned about stability/cracking of the thinner dies. Perhaps AMD is doing the same here, thinning the compute die, then stacking the memory die on top to end up with a stack that's exactly the same thickness as before. Since they're bonded together, the structural integrity should be similar. That additionally has the advantage that you can keep using the exact same IHS as before.
  - formerly_proven 5y ago
    Updates from the article: > - The processor with V-Cache is the same z-height as current Zen 3 products - both the core chiplet and the V-Cache are thinned to have an equal z-height as the IOD die for seamless integration > - As the V-Cache is built over the L3 cache on the main CCX, it doesn't sit over any of the hotspots created by the cores and so thermal considerations are less of an issue. The support silicon above the cores is designed to be thermally efficient.
willis936 5y ago
"On top" in a flip chip means on the side facing the package. The silicon substrate's closest layer is the bottom layer, which is the hottest and still the closest to the IHS.
MrFoof 5y ago
Cutress addresses thermal design of TSVs vs Intel Foveros: https://youtu.be/FqmcWOVv2eY?t=383 https://youtu.be/FqmcWOVv2eY?t=383 There's additional silicon stiffeners which should help with thermal transfer, granted at lower thermal efficiency than a single element. ----- Cooling? Well, I'm using a 5900X right now, air cooled, with a high airflow case loaded with slow spinning 140mm case fans. In games at 1440p120 (maxed settings, with RTX) I'm hotspotting at -- wait for it -- about 68C. With most of the CPU at 60C. In CPU intensive applications, more like 74C hotspot, with most of the chip at 65-67C. That's a setup that's still inaudible to me at 1m distance. I feel this is going to be a 5900XT and 5950XT. Fills a price gap between the higher end X desktop CPUs and Threadripper for the HEDT market. Great for reasonably priced dev desktops (without falling down the workstation rabbit hole), as compilers love cache. ... though next year with 64-core EPYCs at 5nm with 768MB of L3? Oh. Dear. What's in the Xeon pipeline that can attempt to compete with A CPU that dominates on PPW and will be neither cache-starved nor core-starved? I guess it'll fuel a lot of Optane 5800-series sales, as driving down IO latency to sub-10μs will matter more.
ksec 5y ago
They are not putting a layer of SRAM on top of the Core Hotplate. They are putting the SRAM on top of the SRAM section.

How do the thermals work out? The compute dies are already one heck of a hotplate, putting an entire layer of insulating silicon on top isn't going to improve things?

deleted 5y ago

[deleted]

ido 5y ago

I recall years ago IBM had an experimental solution to that that involved liquid in between the layers to transport the heat (vague memory, I think they used an analogy to blood). A quick googling brings up this article, which I think may be the same thing: https://www.bbc.com/news/science-environment-24571219 https://www.bbc.com/news/science-environment-24571219

baybal2 5y ago

There are copper to copper connections in between dies.

bullen 5y ago

I'm pretty sure the longevity of chips manufactured now is going to be alot shorter than for older chips if you can run them at the same temperature! Both litography and the desperate search for infinite growth is going to hurt in the long run! I'm stacking up on 14nm Atom that I can passively cool at 42 degrees celcius full blast on 8 cores and 50nm (100.000 writes per bit) X25-E SSDs!

nicolapcweek94 5y ago
Got any specs on those Atoms? A passively cooled homelab build sounds pretty interesting...
- timeinput 5y ago
  I have [1] which has a similar chip to what the parent described. Its a fun little computer. [1] https://www.newegg.com/supermicro-mbd-a1sri-2758f-o-intel-atom-c2758-2-4ghz-cpu-tdp-20w/p/N82E16813182855 https://www.newegg.com/supermicro-mbd-a1sri-2758f-o-intel-at...
- bullen 5y ago
  It's the SuperMicro ones from 2017.
- Marsymars 5y ago
  I'm planning on building a mini-ITX Atom-based system in the future either with a Jasper Lake (Pentium N6005) or a future Alder Lake-L CPU. ASRock makes mini-ITX motherboards with integrated Atom CPUs that are a bit more modern than Supermicro offerings.
  - bullen 5y ago
    I'm not waiting for an eventual tiny improvement in Gflops/watt... the SuperMicro boards are really industrial and the Atom line is being cancelled for a low wattage version of the consumer chips! I think these boards are the first and last to be able to run 100 years! Earlier models consume too much energy and subsequent will be too fragile/complex!
bayindirh 5y ago
> I'm pretty sure the longevity of chips manufactured now is going to be alot shorter than for older chips if you can run them at the same temperature! Don't be so sure. If it was going to be the case, we'd be changing CPUs like early Seagate disks at our datacenter. There's no measurable longevity loss in the CPUs that we observed in our data center. We use every system for ~7 years at full load.
- bullen 5y ago
  What temp you got on those machines? Since you haven't tried the 7nm CPUs yet I guess we'll have to see? 7 years sounds really short to me, I'm planning on running my machines for 100 years!
  - bayindirh 5y ago
    Just looked to a bunch of Xeon Gold 6258Rs. They're running around ~70 degrees Celsius per die. The machine is under full load. I'm sure its fans are at full speed. That CPU's reported temperatures are 81 for high, 91 for critical (in degrees Celsius). We get new systems almost every year, so we have a rolling set consisting many systems. So, we have a cross section of systems to observe.
    - bullen 5y ago
      My rule of thumb is "if hardware is too hot for you to hold your finger on it indefinitely" it's too hot and it's going to break very soon! Temperature kills hardware, you need to bring those temperatures down, and the only way to do that is to lower the wattage! Atom is the perfect design, no crap and low power!
      - bayindirh 5y ago
        > "if hardware is too hot for you to hold your finger on it indefinitely" it's too hot and it's going to break very soon! From my experience, that doesn't happen like that in enterprise hardware. Either wrong voltage (inside the system) or defective design causes premature death. If the server BMC says it's fine, it's fine. > Temperature kills hardware, you need to bring those temperatures down, and the only way to do that is to lower the wattage! High Performance Computing doesn't work like that, unfortunately :) > Atom is the perfect design, no crap and low power! I'm sure it has its own uses and can accomplish a lot, but in HPC, it won't cut it. I use small SBCs at home to do and try a lot of fun and useful stuff, but it has limits.
grandinj 5y ago
The wear on most electronics is more dependent on thermal __cycling__ than it is on temperature, assuming it is run without it's operating temperature regime.
ryder9 5y ago
[citation required], make claims based on data not on your feelings

IshKebab 5y ago

Silicon isn't that bad of a conductor, and given that it is very thin I'd guess it doesn't affect things too badly.

amelius 5y ago

Thermal resistance is linear in thickness, so if the Si on top is very thin, then perhaps it doesn't matter too much?

flumpcakes 5y ago

Silicon is a crystal, and like metals it conducts heat very well. Copper 400 W / m K Aluminium 230 W / m K Silicon 150 W / m K Iron/Steel 50 W / m K

formerly_proven 5y ago
These devices are often thermally constrained as it is, so the question how this (adding extra silicon on top of the existing die [1]) affects thermals is important. Also neither copper nor silicon are responsible for the "bulk" of the heat transfer - the goal is always to get to a heatpipe or vapor chamber near you as quickly as possible, because those deliver well above 10000 W/m*K. [1] Though Intel thinned their dies recently to improve thermal performance (CPUs are flip-chip, so the metal layers and active circuitry are facing the interposer). Some were concerned about stability/cracking of the thinner dies. Perhaps AMD is doing the same here, thinning the compute die, then stacking the memory die on top to end up with a stack that's exactly the same thickness as before. Since they're bonded together, the structural integrity should be similar. That additionally has the advantage that you can keep using the exact same IHS as before.
- formerly_proven 5y ago
  Updates from the article: > - The processor with V-Cache is the same z-height as current Zen 3 products - both the core chiplet and the V-Cache are thinned to have an equal z-height as the IOD die for seamless integration > - As the V-Cache is built over the L3 cache on the main CCX, it doesn't sit over any of the hotspots created by the cores and so thermal considerations are less of an issue. The support silicon above the cores is designed to be thermally efficient.

willis936 5y ago

"On top" in a flip chip means on the side facing the package. The silicon substrate's closest layer is the bottom layer, which is the hottest and still the closest to the IHS.

MrFoof 5y ago

Cutress addresses thermal design of TSVs vs Intel Foveros: https://youtu.be/FqmcWOVv2eY?t=383 https://youtu.be/FqmcWOVv2eY?t=383 There's additional silicon stiffeners which should help with thermal transfer, granted at lower thermal efficiency than a single element. ----- Cooling? Well, I'm using a 5900X right now, air cooled, with a high airflow case loaded with slow spinning 140mm case fans. In games at 1440p120 (maxed settings, with RTX) I'm hotspotting at -- wait for it -- about 68C. With most of the CPU at 60C. In CPU intensive applications, more like 74C hotspot, with most of the chip at 65-67C. That's a setup that's still inaudible to me at 1m distance. I feel this is going to be a 5900XT and 5950XT. Fills a price gap between the higher end X desktop CPUs and Threadripper for the HEDT market. Great for reasonably priced dev desktops (without falling down the workstation rabbit hole), as compilers love cache. ... though next year with 64-core EPYCs at 5nm with 768MB of L3? Oh. Dear. What's in the Xeon pipeline that can attempt to compete with A CPU that dominates on PPW and will be neither cache-starved nor core-starved? I guess it'll fuel a lot of Optane 5800-series sales, as driving down IO latency to sub-10μs will matter more.

ksec 5y ago

They are not putting a layer of SRAM on top of the Core Hotplate. They are putting the SRAM on top of the SRAM section.