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Does DDR2 really take less power?

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Foxie3a

Normal Member
Joined
Sep 7, 2003
I've been making the switch to LGA775 so I've been looking at DDR2. In the specs somewhere they usually say that DDR2 takes somewhere around 20% less power to run. I've also seen this said about the prescott compared to the northwood because the prescott can run anywhere from 1v to 1.4v, where the northwood typically starts at 1.52v, but we all know the prescott takes many more amps.

I had a PSU problem, and I sent it in for an RMA. I didnt want to be stuck on my laptop so I put the 350 watt in from my P2 system. It has a 12a 12v line, and it's powering a 530J, 2 hard drives, and an X700 Pro. It's JUST BARELY able to handle it. My benchmarks are really showing a lack of power though, I really hate doing this, hopefully my power supply will be here soon. I am running a hybrid LGA775 board for now, and my DDR2 came. It's 512x2 PC2-5400. Currently I am using the RAM in my sig, which is only 256x2.

I put in the full gig and I was able to get into windows, I ran a sandra mem bandwith test, I think I got around 3gb/s, them the system turned off. Sounds reasonable, I can't expect much out of the 350watt. So then I took a stick out and ran only one 512mb stick. It turned on, then off. It just couldn't power it. I put my old RAM back in, and it did it just fine. I was running them DDR2 at the same speeds as the DDR1, and there was the same amount of it(512mb), yet it couldn't power the DDR2.

So to me it looks like DDR2 does take more juice to run than DDR1. I wanted to know for sure though. My DDR1 runs at 2.6v, while my DDR2 was at 1.8v.

This will be my 3,000th post! Woo Hoo! :)
 
Naw, DDR2 uses less power for sure. Infact, DDR2 sodimms use the exact same chips as desktop DDR2 sticks. The only diff is the PCB of course. Whereas laptop DDR1 ram is usually specially made lower voltage sodimms.

Probably some other component that is more sensitive to the lack of juice.
 
batboy said:
Yep, DDR2 definitely uses less power.

Bit of an old thread but any idea on firm figures? I can only ever see reduced - never firm figures.

looking at transitioning to DDR2 for an embeded system if it uses significantly less power than DDR.
 
kelbern said:
Bit of an old thread but any idea on firm figures? I can only ever see reduced - never firm figures.

looking at transitioning to DDR2 for an embeded system if it uses significantly less power than DDR.


Most DDR2 operates between 1.8v-2.1v.

I'm currently running 2.45v through my Mushkin Extreme PC2-6400, 2.45v has taken it from 800mhz 5-3-3-8 to 1000mhz 5-3-3-8.
 
How much current does DDR2 use at those voltages though? If it uses a lot of current it could end up using more power than DDR1. Power = Volts*Amps. He is looking for a the wattage used by DDR2 (nominally). Most estimations I've seen for DDR1 memory such as BH* puts it in the 1 amp ballpark at load.
 
I think that RAM takes more than one amp to run at load. I really have no idea how much RAM takes in general, but I figure that my 3.3v rail is mostly for my RAM, and that's at 40 amps or whatever.

You know how the Prescott runs at around 1.3v instead of the Northwood at like 1.5v... Even though it is a lower voltage there are more amps going into it. However I do not think that that is the case with DDR2. I think that the total wattage is lower with DDR2, atleast that's what it sounds like to me. I'm sure that looking at a whitepaper on some Samsung RAM you could easily tell. I used to have a PDF file on Samsung RAM and it said the voltages and everything of each pin, and all of the other good stuff.
 
Foxie3a said:
I didnt want to be stuck on my laptop so I put the 350 watt in from my P2 system.

Foxie3a, did the psu from the P2 system have the 4pin auxiliary power connector? I know most old psu's didn't have this, so your inability to power ddr2 may have been because of this and not because there was not enough power.
 
This thread is from a long time ago, and I honestly don't really remember. I don't think that it did though.
 
Foxie3a said:
I think that RAM takes more than one amp to run at load. I really have no idea how much RAM takes in general, but I figure that my 3.3v rail is mostly for my RAM, and that's at 40 amps or whatever.

You know how the Prescott runs at around 1.3v instead of the Northwood at like 1.5v... Even though it is a lower voltage there are more amps going into it. However I do not think that that is the case with DDR2. I think that the total wattage is lower with DDR2, atleast that's what it sounds like to me. I'm sure that looking at a whitepaper on some Samsung RAM you could easily tell. I used to have a PDF file on Samsung RAM and it said the voltages and everything of each pin, and all of the other good stuff.

40amps* 2v(DDR2)=80 watts. Not so
DDR400 only need about 15 watts. so amp= 15watts/2.7v(DDR)=5.56amp.
DDR2 should :amp=2.1/2.7*5.56=4.32 amp.
 
I don't think that math works out OCHungry. The only way to find out the amperage pulled by a circuit is to measure it. It varies from IC to IC. Comparing DDR1 to DDR2 for current draw rates is like comparing an Athlon 64 to a P4. The entire design is so different that theres no reasonable base to compare them on.
 
I have never read that DDR2 use less power. DDR2 uses less voltage. As Moto said power=volts.ampers. If DDR2 use more ampers than DDR1, it would use more power than DDR1. I think DDR2 use more ampers than DDR1
 
Thanks a lot Tareek.

Higher pre-fetch reduces core cycle time and reduces DRAM core power usage . Lower I/O & core voltage reduces overall power usage, thus reduces heat generation . 1KB page reduces activate power usage . Option to disable DLL, reduces powerdown power usage .

So basically, because DDR2 uses QDR (Quad Data Rate) technology, it runs at a lower clock than DDR1 for the same theoretical bandwidth & therefor uses less power. At the same clock speed however, current DDR2 technology should (read: probably will) use more power than DDR1 because of increased current draw caused by increasing the clock speed (someone needs to find some info on DDR2 800 power draw as it is 200MHz x 4), but it can provide higher performance at that point making it a good power/performance trade off... in theory.
 
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