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AMD Bulldozer and Extreme Memory Overclocking

post #1 of 25
Thread Starter 
So after reading a bunch of articles and such on CPU design and theory I decided to do some testing.

Biggest Con with the Bulldozer - Super deep pipelines - very high latency at low frequency

The idea behind the deep pipelines is that you will be able to greatly increase frequency that it runs at, which with greater clockspeeds you will be able to (ideally) overcome the biggest drawback of deep pipelines (latency and calculation errors)
So from my understanding, if there is a CPU calculation error, or the CPU is stalled, it can dump the info to RAM and retry, instead of completely flushing the thread and starting over. So with this in mind, here is what I tested.
I solely used Cinebench 11.5 because it is easy to see the progress of the benchmark (which blocks are being rendered, and if one of the threads stalls out, or slows down greatly compared to others)

System, Gigabyte 990FX UD3, AMD FX 8150, RAM Kingston Hyper X Genesis 1866Mhz Edited: 4GB Ram Modules

First Test: 1 Ram Stick @ 1866Mhz, CPU Speed @ 4.6Ghz, Max Score 6.02
Second Test: 2 Ram Sticks @ 1866Mhz, CPU Speed @ 4.6Ghz Max Score 7.40

After watching Cinebench run at stock speeds (3.6Ghz, 1333Mhz RAM with Turbo disabled) You could see some of the threads stall out or stop completely. It could also take up to 6 Runs of Cinebench before you could see what your high score is. (Which from my observation could be up to 0.30 points in difference)

Further Testing (3.0Ghz CPU Speed because I will be lowering the HTT and NB speed and didn't want to create a large bottleneck for my testing.)

1st - 3.0Ghz, 1866Mhz Ram - Same effect, up to 6 runs of Cinebench before Max Score, better performance than 1333Mhz Ram
2nd - 3.0Ghz, 1866Mhz Ram, 2200Mhz NB and 2600Mhz HTT, up to 5 runs of Cinebench before Max Score.
3rd - 3.0Ghz, 1866Mhz Ram, 2200Mhz NB and 2200Mhz HTT, up to 4 runs of Cinebench before Max Score. Close to Max Score on 1st Run.
4th - 3.0Ghz, 1866Mhz Ram, 2000Mhz NB and 2000Mhz HTT, up to 4 runs of Cinebench before Max Score. Closer to Max Score on 1st Run

5th - 3.0Ghz, So for this run, I wanted to get as close to 1866Mhz for Ram, NB and HTT. So I set everything to 1600Mhz and then increased the FSB to get to 1866Mhz, then reduced the Multi back down to 3.0Ghz for the CPU. For this run, I was able to get the Highest Cinebench Score on the first attempt. The score was also 0.15 points higher than the max I got at the previous settings.

3.0Ghz is about the area that has the largest benefit from 1866Mhz Ram, mainly I suspect, due to having to lower the NB and HTT settings to get the most efficient CPU operation. What I presume, is that if you run your Ram in the 2200 - 2400Mhz Range and match it to the NB and HTT, that you will get incredible Bulldozer Performance while overclocking (Much better IPC). And will also be able to run the NB and HTT at the proper speed.

Since the Max my Ram will run is 1866Mhz, without overclocking. I was wondering if anyone could help with my theory. Someone who is more familiar with Overclocking Ram, and also has some rated for higher frequency, 2000+Mhz. Lower latency Ram would be a bonus.

Thanks.
Edited by ComputerRestore - 3/26/12 at 7:26am
post #2 of 25
hmmm interesting..... the score difference you mentioned with same cpu frequency @ 4.6ghz and 1 stick vs 2 sticks of ram is a huge jump. Kinda strange. Maybe cinebench requires a large amount of ram and one stick cant hold the whole program so it slows it down while waiting for the ram to load the info to the cpu… I have an 8120 but only have 1600mhz ram but I guess I could try to get my ram to 1500mhz or so CL7 and see if low timings effect it? It will have to be a little later if not then tomorrow or so but I will do what I can
Edited by dstoler - 3/25/12 at 4:52pm
    
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post #3 of 25
Thread Starter 
Quote:
Originally Posted by dstoler View Post

hmmm interesting..... the score difference you mentioned with same cpu frequency @ 4.6ghz and 1 stick vs 2 sticks of ram is a huge jump. Kinda strange. Maybe cinebench requires a large amount of ram and one stick cant hold the whole program so it slows it down while waiting for the ram to load the info to the cpu… I have an 8120 but only have 1600mhz ram but I guess I could try to get my ram to 1500mhz or so CL7 and see if low timings effect it? It will have to be a little later if not then tomorrow or so but I will do what I can

Awesome, any input would be great. I'm sure any reduction in latency would give some benefit.

You make a good point about the Ram size. I did forget to mention that I was using 4GB DIMMS. So in this case I don't think it was bottlenecking Cinebench due to insufficient volume.
post #4 of 25
I am interested to see what can be achieved with the new Samsung 30 nm 1.35v RAM with an FX. This stuff runs at some crazy high frequencies, but seems to be limited as far as tightening timings. I am currently running it @ 1732 Mhz 8-8-8 1.35v on my 555 platform. Anybody have a report on what the Samsung Wonder RAM can do in an FX platform?
    
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post #5 of 25
post #6 of 25
Thread Starter 

Great review.
I kinda wish they ran other benchmarks to see the CPU scaling with the Ram increase. I wonder how their testing went. If they increased the NB from 2200Mhz to help with the Memory Overclock, I can see from the CPUZ pic that they increased the FSB to 280, but they must have lowered the Multi on the NB and HTT to keep it stable.

Isnt' the i7 2600k NB rated for 3200Mhz or something crazy? I could see why it scaled so much better.
Quote:
Originally Posted by Jagged_Steel View Post

I am interested to see what can be achieved with the new Samsung 30 nm 1.35v RAM with an FX. This stuff runs at some crazy high frequencies, but seems to be limited as far as tightening timings. I am currently running it @ 1732 Mhz 8-8-8 1.35v on my 555 platform. Anybody have a report on what the Samsung Wonder RAM can do in an FX platform?

Wow. That is much better than my Kingston Ram. 1.65v @ 1866 9-10-9-27 timings. Seems pretty easy to OC too. I am going to buy a set to do further testing.
Edited by ComputerRestore - 3/26/12 at 9:28am
post #7 of 25
I am totally wowed by this Samsung memory. I picked my 8 GB set up last week at Fry's for $39.99. This stuff actually auto booted @ over 1900 mhz on my rig when I set the voltage @ 1.65 and all auto settings. I made a few posts about my first impressions here and here. There is a good review and a long thread about it over at Tech Power Up .

I made this post about it this morning:
Quote:
Originally Posted by Jagged_Steel View Post

It appears that heat sinks on RAM are going to be a thing of the past with the next generation of 30 nm ICs. I just got a set of the Samsung 30 nm Wonder RAM, and they do not get hot to the touch at all, even after hours of intense stress testing, compared to my last set, a 4 GB Corsair XMS 2000 Mhz set, which do get warm after that kind of usage. This RAM costs $39.99 and is the bomb, by the way. I was leery about the reports on these, but now I can attest that these little gems really do live up to the hype. Look a the second pic, these things are barely as tall as the retainer clips, compared to top last generation RAM with the giant bulky heatsinks. Tech baby! thumb.gif

240240

Samsung 8 GB 30 nm RAM

Better pic showing the size of this new RAM compared to some G Skill:
447

I would love to see some benchmarks of it on a nice FX machine with the better frequency capabilities compared to my old PhenomII.
    
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post #8 of 25
Quote:
Originally Posted by Jagged_Steel View Post

I am totally wowed by this Samsung memory. I picked my 8 GB set up last week at Fry's for $39.99. This stuff actually auto booted @ over 1900 mhz on my rig when I set the voltage @ 1.65 and all auto settings. I made a few posts about my first impressions here and here. There is a good review and a long thread about it over at Tech Power Up .
I made this post about it this morning:
I would love to see some benchmarks of it on a nice FX machine with the better frequency capabilities compared to my old PhenomII.


Not sure why you need 1.65v at 1900mhz... you can hit 2133mhz with 1.5 and 2400mhz with 1.55-1.575.

 
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post #9 of 25
Quote:
Originally Posted by djriful View Post


Quote:
Originally Posted by Jagged_Steel View Post

I am totally wowed by this Samsung memory. I picked my 8 GB set up last week at Fry's for $39.99. This stuff actually auto booted @ over 1900 mhz on my rig when I set the voltage @ 1.65 and all auto settings. I made a few posts about my first impressions here and here. There is a good review and a long thread about it over at Tech Power Up .

I made this post about it this morning:

I would love to see some benchmarks of it on a nice FX machine with the better frequency capabilities compared to my old PhenomII.


Not sure why you need 1.65v at 1900mhz... you can hit 2133mhz with 1.5 and 2400mhz with 1.55-1.575.

On Intel rigs. Trust me, 1900Mhz is off the charts on my 555 at any voltage.

440

Edit to add: Not sure if you are just completely uninformed or trolling.

273
Edited by Jagged_Steel - 3/26/12 at 10:23am
    
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post #10 of 25
Thread Starter 
So, my Samsung WonderRams are on order. When I get them I hope to start with 2200Mhz to see how it helps with Bulldozer overclock scaling.

As those that do Overclock the Bulldozer (8 Core versions) know, there is a sweet spot where performance increases exponentially instead of linearly. Depending on the chip, it can be from 4.8hz to around 5.0Ghz.

What I hope to achieve (in theory) with the Ram overclock and NB, HTT matching, is to lower the point in which the exponential performance gains start.

From my calculations so far, 1866Mhz Ram, HTT and NB are a match for 3.0Ghz on my FX8150. (Gives the best IPC at this frequency with 1866Mhz Ram, increasing or decreasing NB, or HTT lowers performance, and lowering Ram Frequency lowers performance)

So I estimate if I can run 2400Mhz Ram stable, and match it to HTT and NB, I should be able to have exponential gains on performance from 4.2-4.4Ghz compared to 4.8-5.0Ghz.

The main reason to run the Ram so high, is because matching the Ram, HTT and NB at 1866Mhz really bottlenecks performance at high overclocks and causes system instability. So ideally 2400Mhz is the middleground between 2200NB and 2600HTT.
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