Question Do I need a memory cooler for big amount memory installed

[sheremet.09.05]

Hello everyone. I have a typical question: "Do I need a memory cooler" and the typical answer is "No because there is enough cool air inside PC case."

But...

What about the question "Do I need a memory cooler for big amount memory installed?". Here is PC power consumption calculator shows 128GB DDR4 x 1 requires 500-599 watts while 128GB DDR4 x8 requires 800-899 watts (for same motherboard and processor). So difference is about 300 watts and this looks like an additional HEDT processor installed in the motherboard.

How Much Power Does Memory Use? says that every 8Gb DDR3 consumes 3 watts so 128GB DDR3 x 8 consumes about 384 watts. That looks very similar to DDR4. Anyway, a threadripper processor that consumes 280 watts must use a very big cooler or liquid system but what about memory that consumes 300 watts? Is it still enough to use them without additional cooling or not? Workstations with threadripper processors like P620 from Lenovo have an additional 2 fans for memory cooling.

What do you think about this? Any proof for manuals or already built PCs are welcome!

Thanks in advance!

 

[Aeacus]

while 128GB DDR4 x8 requires 800-899 watts

🤣

You got played.
PSU calculators aren't accurate and they show general estimation of the whole build. Also, you read the Crucial info wrong. Just because one 8GB DDR3 DIMM consumes 3W, doesn't mean 16 GB DDR3 DIMM consumes double of that.

Here's research about your question,
link: https://www.servethehome.com/ddr4-dimms-system-power-consumption-tested/

Whereby;

For those that want the hard numbers:

• 16x 8GB 232W
• 4x 8GB 205W

However;

Caveat to This Measurement

Our diligent readers likely noticed a caveat in this analysis. We are measuring not just the power consumption of the DDR4 RDIMMs, but also the power consumed by the server itself.

So, when 16x DIMMs + whole server consumed 232W but 4x DIMMs + whole server consumed 205W, that means that the 12x DIMMs removed reduced it by 27W.
27W divided by 12 DIMMs = 2.25W per one 8GB DDR4 DIMM.

With that, 16x 8GB DDR4 DIMMs (total of 128GB) consume 36W as total.

Do you need active cooling for 36W? You tell me. 🙄

 

[sheremet.09.05]

You completely misunderstood the question.

So, when 16x DIMMs + whole server consumed 232W but 4x DIMMs + whole server consumed 205W, that means that the 12x DIMMs removed reduced it by 27W.
27W divided by 12 DIMMs = 2.25W per one 8GB DDR4 DIMM.

1) I am telling you exactly the same. For PC power I told about the difference: 800-500=300 watts for DDR4 modules. It does not mean that 8 DDR4 consumes 500 or 800 watts - it means that 8 DDR4 consumes about 300 watts. (Actually, 7 modules consume 300, because comparison 1 and 8 modules installed so 8 modules will consume about 350 watts )

With that, 16x 8GB DDR4 DIMMs (total of 128GB) consume 36W as total.

2) I am talking about 8 modules with 128GB, e.g. 2048GB in total this is not the same as 128GB. But even with that 2048/128=8, so 8*36=288

So, Do you need active cooling for 36W 288W? You tell me. 🙄

 

[Aeacus]

If you're using U2 server rack, then having a fan or two over the RAM DIMMs helps the otherwise poor airflow in the rack. Hence why servers can have fans there (there is space over RAM DIMMs for fan placement).

it means that 8 DDR4 consumes about 300 watts. (Actually, 7 modules consume 300, because comparison 1 and 8 modules installed so 8 modules will consume about 350 watts )

DDR4 operates at 1.2V to 1.35V and pulls 1-2A. That translates to 1.2W to 2.7W per one DIMM, regardless the capacity.
TH testing of DDR4: https://www.tomshardware.com/reviews/intel-core-i7-5960x-haswell-e-cpu,3918-13.html

So, if you use server MoBo with 16 RAM slots and populate all with 128GB RAM sticks (to get 2048 GB total), that operates at 1.35V (Supermicro 128 GB stick operates at 1.2V, specs) and IF the RAM would pull 2A, it would be: 16 DIMMs * 2.7W = 43.2W. Running 1.2V and when considering 2A per DIMM, would translate 2.4W per DIMM. Or 38.4W for all 16 DIMMs.

Like i said before, at most, for 16 DIMMs, you're looking at a bit over 40W of power consumption at most. Not the mythical 300+W you claim.

But even with that 2048/128=8, so 8*36=288

Your math is wrong. 2048/128=16 and not 8. Use the calc built in to Win.

Also, if you were to believe your own math regarding RAM power consumption (300W for 7x DIMMs), one DIMM should be pulling 42.8W, which for 1.35V would be 31.7A. Or at 1.2V, it would be 51.4A.
30-50 Amps per one DIMM? Doesn't happen.

 

[bit_user]

8 DDR4 consumes about 300 watts. (Actually, 7 modules consume 300, because comparison 1 and 8 modules installed so 8 modules will consume about 350 watts )

This cannot be true. Just look what kind of CPU cooler you would need to dissipate 350 W. At that level, mere air cooling cannot do it - you need to go liquid cooling or use something like a GPU cooler.

Here's a 128 GB DDR4 DIMM - it should tell you something that it doesn't even have a heat spreader!

Source: https://www.newtownspares.com/mta14...MI95uYm8KNgQMVgUxHAR1k7gneEAQYASABEgIfmPD_BwE

Specs: https://www.micron.com/products/dram-modules/rdimm/part-catalog/mta144asq16g72psz-2s6
​

At this point, I'd be questioning the accuracy of anything that PSU calculator is telling you.

BTW, the only DDR4 modules with 128 GB capacity are server memory modules (i.e. RDIMMs or Registered DIMMs). Most of these PSU calculator apps are probably designed for desktop builds & components (i.e. UDIMMs or Unbuffered DIMMs), in which case it shouldn't be too surprising that it's way off. The "Register" in RDIMMs exists to reduce current demands, at the expense of additional latency.

Workstations with threadripper processors like P620 from Lenovo have an additional 2 fans for memory cooling.

Server memory is designed for use in server chassis that move a large volume of air through them. It therefore makes sense that you would want some direct airflow across your DIMMs, especially if you're going to pack those slots full.

Fortunately, modern memory modules have embedded temperature sensors that you can use to get a sense of how effectively they're being kept cool. If they're getting near or outside the specified operating envelope of the memory, then you'll know you need to improve heat dissipation from that area.

 

[sheremet.09.05]

Many thanks for reasoned responses

 

[bit_user]

Many thanks for reasoned responses

Good luck with your build!

I agree with your assessment that it should have some airflow directed at the memory. Furthermore, keep an eye on those RAM temperatures. In Windows, there are numerous tools (HwInfo64 is one that comes to mind) that can tell you memory temperature.

On Linux, you can read DIMM temperatures using the sensors command, once it knows how to find them. I found this link which might be helpful. I'm sure I've seen sensors report DIMM temperatures without me ever running i2cdetect or sensors-detect however. Maybe it has built-in knowledge for some DIMMs.

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Reddit - Dive into anything

www.reddit.com

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[Zerk2012]

Many thanks for reasoned responses

SK hynix Official Product Website

RDIMM/LRDIMM | SK hynix Official Product Website

product.skhynix.com

Our 256GB DDR4 RDIMM consumes around 8.5W of power and LRDIMM around 10.5W, both the most competitive levels in the High Density Module market.

That says a lot different then anything else of course it could very some by brand.

I can tell you another thing people don't build a 20K PC you let a specialist build it then every problem is on them not you.