RAM heat

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RAM heat

Post by michaelb » Mon Mar 08, 2010 11:48 pm

Have read, and seem to have experienced, that ram is a significant source of heat, and therefore noise.

For those who have already experimented or know, would two 256MB SODIMMs of PC133 be hotter than one stick of 512? By a lot? All have 8 chips.

Similar for DDR2 667mhz SODIMM, 2G vs. 1G + 1G.

Or (2G stick) vs (1G stick) if same # of chips. Is it double the heat, almost double, almost the same, or the same?

Has anyone left ram out because of heat? Like stopping at 512 or 1gb, instead of going to 2-4gb, even on dual core systems? Or only using your "big" stick of memory, since your other is 1/4 the size but (?similar?) heat?

Anyone know the wattage of ram, compared TDP of cpu, which might be 25-35 for my laptops. But much lower when undervolted/idle/speedstepped down, not sure ram can do that.

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Post by Parappaman » Mon Mar 08, 2010 11:56 pm

A stick of desktop 2GB ddr2 ram usually takes no more than 6-7w unless taken to insane levels of voltage (like 2,3v). A few less for single-side memories. A few less than that for SODIMMs. Don't know where you did read that they are a significant source of noise... :P All I can say is that those selling so-said "green" and "low power" memories are simply overpricing the cheap ones.

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Post by ilovejedd » Tue Mar 09, 2010 12:09 am

From one of the earlier research I've done:

Kingston 2GB DDR2 800 SDRAM CL6 KVR800D2N6 - 2.016W/stick
Kingston 2GB DDR2 800 SDRAM CL5 KVR800D2N5 - 1.975W/stick

That's from product specifications. Unless you're using FB-DIMMs or some crazy overclocked gaming memory, I don't think you'd have to worry on that quarter. Hmm, I guess one way to measure RAM power consumption is to put the computer to sleep. There's still some draw from the motherboard but it would be mostly just the RAM that you're powering.

By the way, I somehow doubt RAM goes on idle. If they do, then they'd lose data.

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Post by lm » Tue Mar 09, 2010 2:41 am

RAM is too important to leave out, unless you really want to cripple your system. Rather max out your RAM to make your system fly. That would be 4GB for 32bit systems.

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Post by Klusu » Tue Mar 09, 2010 11:39 am

Idle is one thing. About 1W per stick (DDR2). Load is another thing.
Single sided should draw half of that.

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Post by michaelb » Tue Mar 09, 2010 6:14 pm

1 or 2 watts IS significant!

TDP at low freq for a modern laptop cpu might be 10-15W. 13.1W example: http://www.thinkwiki.org/wiki/Intel_Cor ... 28Yonah%29

Or more if you pick a hungry CPU, but this is SPCR.

If undervolting, then when idling, or between bursts of activity when surfing, maybe there's 4-7W to cool if you're lucky. 1W is huge compared to that.

I am thinking notebook, could have posted there, but thought also applies to HTPC, SFF, etc.

Have read a complaint about a small 3W or 5W LED flashlight, that it gets too warm. You can burn yourself on a 4W bulb.
Klusu wrote:Idle is one thing. About 1W per stick (DDR2). Load is another thing.
Single sided should draw half of that.
So you think #GB doesn't matter, just #chips?

Tested an old 1.1G Mobile-PIII-M laptop (TDP 9.3-21.8 ) today, 512MB + 128MB SODIMM PC133, both 8 chips:

about 12W moving the mouse around, 15ish surfing, 23.5 or 24W running memtest.

Removed the 128M sodimm, and since the kill-a-watt has no decimal pt on watt, &/or since watts jump, couldn't see a difference except in memtest, dropped to around 22.5 W.

Had there been a big difference, it may have been ok to leave out my 128M card, since Linux runs fine on 512, and the 128 seems to offer little benefit.

That's even more true on a different laptop with a 2G stick + 1G stick of DDR.

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Post by swivelguy2 » Tue Mar 09, 2010 10:30 pm

RAM doesn't really get hot to the touch unless you overvolt and overclock it. We stick a kilogram of copper on the CPU, otherwise it would burn itself to death. Given these facts, how have you come to conclude that RAM is a significant source of heat and noise?

Anyway, to answer your question, newer RAM is built on smaller lithography processes than older RAM, and will consume less power to do the same work, just like newer CPU technologies. So if you really wanted to minimize the power your RAM is sucking, get 1 stick of the most modern, low-voltage RAM you can.

And then be sure to get a kill-a-watt and compare with more sticks and different voltage-rated RAM and tell us just how much difference there actually is, at idle and at load.

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Post by Klusu » Sat Mar 13, 2010 4:04 am

In theory, power draw (at least part of it) is proportional to frequency. 133MHz RAM may be older, but it never gets hot. But it can do less.
Yes, I think the number of chips is important, not GB.
Idle CPU may draw just a few W, but the computer 50W (OK, a laptop draws less).

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