DDR3 Memory Scaling On AMD's Phenom II X4 : Which RAM Speed Is Best?
Source: Tom's Hardware UK – Keywords: phenom, ii, ddr3
Which RAM Speed Is Best?
DRAM prices have come down in the past few months, making capacities of 4, 6, or 8 GB very affordable. You can get 4 x 2 GB DDR2 memory kits starting at only $80, and even DDR3 is no longer unattainably pricey. However, high-speed memory is still considerably more expensive, and memory vendors want you to believe that DDR3-1600 and faster is what you need, despite the fact that neither Intel's Core i7 or AMD's Phenom II X4 officially support those data rates. We wanted to look into this, and so we ran plenty of benchmarks on an AMD Phenom II X4 955, with all possible memory speeds and different timings.
Where Memory Differs
Two types of Dynamic Random Access Memory (DRAM) technology currently dominate: DDR2 and DDR3 at speeds between 400 MHz and 1000 MHz. DDR stands for Double Data Rate, which means that data is transferred during the rising as well as the falling edge of a clock cycle, which doubles the effective clock rate. The slowest mentioned memory is therefore referred to as DDR2-800 (400 MHz in DDR mode). DDR2 is typically available at speeds up to DDR2-1066 or DDR2-1200, while DDR3 spans DDR3-800 to DDR3-2133+ speeds.
PC memory is available as DDR2 or DDR3 modules, generally called Dual Inline Memory Modules (DIMMs). Notebook memory comes on small outline DIMMs (SO-DIMMs), which are much smaller, but otherwise very similar. Intel’s Core i7 processors support up to three memory channels, meaning you can use three or six memory modules operating in three-channel mode at maximum speed, while most other architectures work with two or four modules in a dual-channel configuration. This applies to AMD’s Athlon 64 X2 and Phenom series, as well as Intel’s Core 2 and Pentium families. Multi-channel modes are an effective way to increase memory bandwidth by aggregating multiple 64-bit links.
Now, you probably know that a memory kit running at a high speed is probably the best choice for a fast system, but you’ll find that there is a plethora of different brands and products, and the differences between them often seem to be small. As a matter of fact, the remaining differences can be found in the voltage level and the supported operating parameters, known as timings. These basically define the number of clock cycles required for each of the key steps in accessing the memory matrix. As a result, greater timing values represent slower execution.
Which Memory Should You Buy?
We will answer this question on the following pages by looking at a modern AMD Phenom II X4 955 system, which we benchmark at many different memory speeds and timings to find the best bang for your buck. We'll be doing the same thing in a subsequent piece for owners of Intel processors, so keep an eye out for that!
- Next page Test System: Phenom II X4 955 And...
On page 3, under Motherboard, I think you meant to write 790FX, not GX, for the chipset.
I don't mean to be rude but this is a somewhat naive article in my view(yeah I know it still sounds rude
sorry!). Lets take a look how memory is tied to the CPU via the FSB, when we speak of 800Mhz FSB etc were not speaking of the speed of the bus but the speed in which the clock ticks right? the whole point of the clock is to keep things in sync otherwise the PC would crash almost constantly because you could be re-populating cache addresses that might still be in use by the last instruction , where am heading with this? well my point here is you could have that memory running at 200000mhz but that data still aint going to the processor until that clock(FSB)ticks.
Geeks love analogies right? here's one that illustrates my point perfectly. Every morning you wake up at 8am and prepare to catch the hourly bus to work this runs at 30 mins past the hr and usually gets you to work for 9am. On monday you have that monday feeling as a result your in a bit of a daze therefore it takes you 20 mins to prepare before going for the bus. Tuesday you have that fire back in you belly, and as a result of running around the house like a mad fool you manage to prepare in 10 mins before going for the bus. which day do you arrive at work the earliest? of course it's a trick question you arrive at the same time because you still have to wait for that flamin' slow bus(FSB)
For the reason outlined above the only time it is worthwhile using faster rated memory than your CPU rated FSB(quad pumped last time I looked) is if you plan to overclock it by increasing the FSB.
The slight improvements you do see in your benchmarks have more to do with reduced latency(not to be confused with speed)than any speed increases I believe.
PS. I keep thinking of better ways I could have put this across but as this is a comment and not an article it's probably not worth progressing it from the draft stage, hope it makes a lil' sense.
I really dont understand why you guys didn't review ram speeds of 1800, 1866 and 2000, that is what I was expecting and was dissapointed. What puzzles me more is that you did review speeds of 800 and 1066. Anyone who is going to be using a P2 X4 will not be running DDR3 800.
So 1333 vanilla if you have a bit of extra cash otherwise better quality good low latency 1066 is the go?
Can someone suggest a few brands?
Corsair TwinX ?
Phenom 955 is a suits my buget the best. We shall see what the DX11 cards will bring in september- august. then this guy here is going to buy him self an awsome gaming rig on a tight buget. the PC including the monitor should not cost me much more then €900 that is my buget here.
Core i7 might be awsome too you know but it costs more and you need an expansive fan too etc. I really have a hard time to justify any costs on one and another. anyway DDR3 prices are great now. 4GB of 1600mhz memory costs just €3-7 more then the 1333mhz version. So i definatly go for 1600mhz. I got a good system setup so far and it is just great AM3 now happend to be as affordable as am2+ was a few months ago. both AM3 and 1366 offer long term benefits and upgradability. When ever it is gulf town or orochi. I dont care which one is out first but i do care on the long term that i have a computer which is able to sustain its self for a long time. You can see it like this core i7 is a bit faster but costs more. phenom is a bit slower and costs less. however orochi should be a competitor for the gulftown. It happends to be a bit slower ofcourse but it should be cheaper. this might make a great upgrade path. You will have a computer upgrade for €150-250 somewhere in 2010-2012 depending on what you want to spend on new hardware and adding a new graphic card as well as a new cpu. I think this is good. However it is imporment to get a good motherboard for that from a manufacturer who is known for updating its bios for newer cpu's or else your screwd over. I perfer both ASUS and Gygabyte for this they are known for having quite a few of there am2 boards supporting am2+ and am3 cpus. Unlike asrock,foxconn and msi who screwd you over at that time not supporting the phenoms.
yep true ideedy i got the gygabyte for my 955 x4 flashed it in 4-5 mins with no problems what so ever
but im not confinced to upgrade my ram settings (still use my 667 ram)i find it all pretty much the same
4 gig minimim the rest on a good gpu