So Logan and Wendell have been talking about RAM speed and AMD cpus. Now I know already it makes a considerable difference with the APUs(not surprising really) but is there any difference with AMD FX CPUs and using high speed RAM?
Not for gaming.
I will add to Nord's comment and say that the best use case for 2400 MHz or higher RAM with an FX CPU is for online video streaming where the extra memory bandwidth speeds up "on-the-fly" video encoding.
Oh, I see. So fast RAM + 8 cores = win?
If you are a video game streamer it can be an advantage but if you aren't streaming directly to the internet I can't really see the need for it.
it does make a differnece, recently just bought some G.Skill Ripjaw X 2133mhz ram at CL9 and i came from Corsair Vengeance 1600mhz CL9. The difference is enormous, what matters is a good balance of latency and speed. I'm able to get a good difference in load times, i render on 3dsmax and maya, i see a good noticeable difference. I know its GPU based renders, but it also relies on the NB, better ram gives better bandwidth on the NB which means better transfer from CPU/GPU related work. Intel the NB doesn't rly matter as much as AMD.
Straight up gaming and not recording stream or rendering. ram speed does not matter enough on FX cpus.
you'll see a <5% increase in frames
Don't forget about RAM disks! I love my 2400mHz RAM; makes RAM disks insane :)
Yes but with AMD it's very selective on what sets of 2x8GB 2400 MHz RAM will work with motherboards, never mind with the memory controllers themselves. The only info I could squeeze out of Asus's website for the M5A99FX PRO R2.0 for 16GB was G.Skill F3-19200CL10Q-32GBZHD Ripjaws Z series if you could find it in 2x8GB pack instead of 4x8GB pack. It will only run a single dual channel for many of the RAM kits over 2133 MHz. If you try to populate 4 slots it throws a ram error on post.
If you ever tried bulldozer, the NB setting ran at 1.2V. This allowed 4 memory modules running at 1.65 no problem. When piledriver was launched, they changed the NB stock settings to 1.175V. Because of that, you get problems with the RAM wanting to run @ 1.65V if you have 4 sticks. It's not the speed but more the voltage given. If you run 1.5V you ccan have 4 sticks no problem. So to fix that all you need to do is run the NB back to 1.2V and you can do 4 sticks running @ 1.65V no problem. idk why they didn't put a string on the XMP to adjust voltage of NB whenever it requires more than 1.505V.
haha...np, well when bulldozer came out, the chip was more power hungry on the North Bridge side. It uses 1.2V, The North Bridge tends to dictate the connection between the CPU, RAM, and Video Card. What we're focusing about is the connection from CPU to RAM. When you raise voltage on the North Bridge, you can increase clock and amount of RAM used. The problem when you get high clocked RAM on Piledriver is because they use 1.175V instead of Bulldozers 1.2V. Like earlier you stated that running 4 RAM modules was a problem because it wouldn't be stable. The reason is because not enough voltage is fed to the North Bridge to handle high clocked RAM. The reason is because most lower clocked RAM requires 1.5V. Running 4 modules @ 1.5V is no problem, but when it requires anything above that like 1.65V which is pretty much how all high clocked RAM are. This puts more strain on the North Bridge,
So if you're doing 4 1.65V modules then you're using 6.6V compared to 1.5V RAM which would be 6V. Math wise 6 / 1.175 =5.106 and 6.6 / 1.175 = 5.617. I know these numbes don't make much sense, you'll see in a second. Now we take the NB @ 1.2V and we get 6 / 1.2 = 5 and 6.6 / 1.2 = 5.5.
Ok this shows that if you increase the voltage of the north bridge, you will be able to deliver more efficiently the power to the RAM because there is more at disposal. This is a bit arbitrary because RAM doesn't exactly work that way, but the way the north bridge works in that way. Every stick of RAM add's voltage and needs to be given by the North Bridge. The voltage is divided to the whole sum like the math i did above.
I forgot where i read it but a guy posted on overclock.net stating he had problems with piledriver running 4 high clocked RAM modules something like 2400mhz. He solved it because he found out that the FX chip can only allocate no more than 5.5V on the RAM. He used a voltage tester to find out. Whenver voltage went past that on load it would hang and computer would blue screen or just reset. I've never torn apart a bridge or CPU but my guess is that the controller can't handle more than 5.5V. This is were i get lost because i don't know how the power is exactly delivered and divided to each piece of the rail on the socket. I hear Intel is even worse where it can't handle more than 3.5V(z77/z87) or 4.5V(x79). Though Intel has some work around it, so it's no big deal.