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low voltage ddr3

post #1 of 7
Thread Starter 
are there any requirement to run DDR3L / DDR3U at their low voltages on amd platform? ie. what cpu & mobo should i need? i have gskill sniper F3-12800CL9D-8GBSR2 (1.25V) & Athlon II 245 C3
i know that i can run it at 1.5V but just curious what it takes to have it stable at 1.25V

thanks

update: i know AII & PII officially support up to ddr3-1333, but what are the chances of getting AII & PII that can deal up to 1600? or does it depend on the revision & core?
Edited by drabun - 3/10/12 at 8:50am
post #2 of 7
Most C3 deneb are able to get 1600 easily. The thubans can go up to 1866 sometimes.

Maybe a slight bump in cpunb will do 1600
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post #3 of 7
I ran my old Athlon II x2 250 (C2 stepping) with RAM @ 1900, so 1600 will be easy to hit.
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post #4 of 7
Thread Starter 
thanks for the responses

what about cpu's IMC compatibility with low voltage ddr3, can AII and/or PII deal with that?
quick look at cpu-world.com, mobile cpus & opterons are mainly the ones to support DDR3L, & none supports DDR3U
tomshardware review on kingston LoVo (1.35V) confirmed that PII X6 is compatible with 1.35V, & techenclave.com review on gskill sniper (1.25V) confirmed that PII X4 955 BE C3 Deneb is compatible with 1.25V
now, because cpus that are based on the same core & of the same stepping, would have the same IMC design, can i safely conclude that all Deneb-based C3 cpus can handle DDR3U/L? or do i also have to take IMC's revision into consideration?
post #5 of 7
FWIW, testing on both AMD and Intel desktop PCs has shown that with DDR3 RAM there is little to no tangible performance gains in real applications on desktop PCs once you get above ~1333 MHz. Some 1333 MHz. rated RAM will OC to 1600 but not all. LV RAM seems to OC better according to many people but there is no guarantee.

http://www.overclock.net/t/1206332/help-me-through-my-bottleneck-6-7-6-24-1t-1333mhz/20#post_16432691

AMD Llano/APUs are the exception as both the CPU and GPU can access the higher frequency and that does improve real world performance. Increased frequency is best with the APUs. Latencies don't make any tangible diff.

As the frequency increases one clock cycle becomes less and less in real time. Since the DDR3 RAM isn't a bottleneck there isn't much to be gained. Some folks have OC'ed the FX CPU RAM to 2400 MHz. and seen ZIP for performance gains because the RAM is not limiting performance.

Benches will show a little improvement but that doesn't seem to transfer to real apps. for most folks.
post #6 of 7
Thread Starter 
yes, the reason that i bought ddr3 1600 was to pair it with APU, now here are my problems
1. a friend gave me AII 245 C3
because i don't have the money to build the APU sys yet, i intend to delay building the APU sys, & instead set up one based on the AII, hoping that i could sell the AM3 board later
this is why i asked whether AII can run with the ram's stock speed, & it's solved

2. the LV ram
i picked the LV ram simply because less voltage = cooler, i didn't realize that there's dependency between LV ram & cpu's IMC, i thought the diff between DDR3L/U and DDR3 is only at hardware-level (ie. the litho used to build the ram chips), but googling seems to indicate that they also differ on the design-lv

while googling for that dependency, i found this PII/AII/Sempron asus board M4A87TD/USB3, which explicitly states that it supports ultra LV ram, implying 2 things (1) supporting ultra LV ram isn't the norm for amd boards, (2) 1/more of the supported cpus are compatible with ultra LV ram

hence, i think running LV ram has some requirements on the mobo & cpus

once again i emphasize that i don't want to OC the ram, at least not yet, i just want to run it at stock speed & voltage, 1600@1.25V, wondering what it takes to do that
post #7 of 7
yes it will work go for it be sure to set dram voltage in bios
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