on what exactly does PC3L / PC3U ddr3 depend on to run on at 1.35V / 1.25V? i mean, which component(s) support are required? my interest is especially on amd platform
some that i find potential are:
1. cpu's IMC
i actually don't know what IMCs role here because i'm almost completely blind about ddr3 design
but, a quick look at cpu-world.com, amd mobile cpus & opteron are mainly the ones that support DDR3L, & as far as i see, none of them supports DDR3U
so does it mean PII, AII, APU (both k10 & 15 h), FX must run such ddr3 at least at 1.5V?
i'm guessing this is because it's the mobo that step-down the DC voltage to the vDIMM
an example of a mobo that explicitly states its support for PC3U is asus M4A87TD/USB3 (), so i guess supporting low-voltage ddr3 is the exception, hence mobos that don't specify this must run such ddr3 at 1.5V or higher, right?
now, the M4A87TDUSB3 product page states PII, AII, Sempron are supported, which implicitly says that one/more of those cpus support low-voltage ddr3
3. mobo chipset
i don't know how this correlates with low-voltage ddr3, but let's throw it into our topic just to make sure
from a few that i looked, mobos that support low-voltage ddr3 use amd 8-series chipsets / higher, does anybody know one that uses amd 7-series?
another question is PC3L & PC3U ddr3 are required to be able to run at 1.5V aside from their lower voltages, do all those low-voltage ddr3 on the market comply to it? (ie. they won't break at 1.5V right?)
I'm no expert, but I know a lot of people have low voltage DDR3 on common motherboards. A lot of motherboards probably jsut weren't tested with the low voltage modules. Also, a lot of server motherboard/ Xeon/Opteron CPU combos support unbuffered DDR3.
No low voltage module should break at 1.5v, a lot of people overclock many of them past 1.5v and up to 1.65v or even 1.7v. Whether or not all low voltage modules can do this is not guaranteed, but many low voltage kits are known to be huge overclocking kits.
Newegg.com has a G.Skill 1.25v DDR3-1600MHz 9-9-9-24 2x4GB memory kit currently selling for $50, you could look through the reviews for what hardware the buyers used. Last I checked it was up to 180 reviews and had a five star average, so it can't be difficult to use it on most hardware.
I haven't looked at similar 1.35v kits in a while, so I can't vouch for them right now. As for specific chipset support? It should just depend on whether or not the motherboard's BIOS lets the memory voltage go down low enough. If it doesn't then just overclock the memory and it should then run stably at 1.5v. Low voltage DDR3 is still held to the same standards as regular unbuffered DDR3 so it shouldn't break until you really pump up the voltage to the point where it would break regular DDR3 modules too.
I've never tried it and I don't know if anyone else has it running. It might not work because AM3 is an older platform that might not have been made with lower voltages than what was out at the time in mind for compatibility. It should work. If not, then it could still be overclocked to 1.5v and it should then be fine. 1.35v memory should work on AM3, 1.25 might need increased voltage, I can't say for sure.
I'll look into it, maybe you could try a Google search while I try mine too.