Originally posted by: Space Marine
First of all a big THANKS for replying.
So to sort and confirm things that i got them right:
I have the C2d 6420 which runs default @ 266 mhz bus. also i don't intend to oc so lets keep stuff stock.
1) Right now the best setting for my DDR400 is to keep it @400.
1b) There's no way setting this ram run in sync with THIS processor right?
2) The best stock DDR-2 ram to buy for this mb is some cas4 DDR2-800 so it runs @533 with even more lower timings ?
2b) In this case it's better running the ddr2-800 @ 533 than @667?
2c) In this case 533? will i be in sync? This sync affects stock performance too or only overclocking scenarios?
And if your not bored how does this 1:1 stuff affects can you explain or gimme a link to read
1) Yes.
1b) Yes. Except you want to take your E6420 back to 200 fsb - you won't do this right?
2) Depends on what timings you want. The lowewst CAS Latency setting on this board is 3 for DDR2. Typically at CL3 people set things at CL3-3-3-8. You can try better timings for the latter 3 settings (i.e. tRCD, tRP and tRAS) and see if it is stable - I haven't tried before. And for the command rate, you can set 1T command and it should be a little bit faster. But if your RAM is not so good you may be unable to be at 1T.
For the other timings, people conern less about them and I am not quite familiar too. The only setting I tried is the tRFC (Row Refresh Cycle Time). The board reads from the RAM's SPD for these less familiar settings. (I think not many boards have such detailed settings for RAM besides ASRock) e.g. For my G. Skill, the default tRFC is at 27T. I remember when I use Corsair DDR400 on this board, this setting is at 13T. So I tried to make it faster, but it seems the lowest value I can achieve is just around 20T. After that I remain this setting in auto, and I haven't tested if there are any impacts on performance.
Most of the RAMs just mark CAS latency at 4 or 5. Very few of them are at 3, e.g. for syncmax, they have an express series which can run at ddr2-533-3-3-3-8, this will be a little bit expensive than the ordinary ones. PQI also has CL3 modules but I seldom see this in the market, and PQI is not a very renowned brand as well. G. Skill and Corsair also has modules marked at CL3 but they are simply rare and extremely expensive. I saw some tests on the ddr2 rams and it seems that quite a number of ddr2-800-cl4 modules can run at CL3-3-3-8 at over DDR2-600+, e.g. G. Skill, Crucial, Corsair, etc. While modules from OCZ, Kingston, or Geil may find it difficult to go up to this.
2b) As long as you are running a 1066-fsb cpu on this board (you can't use 1333-fsb on this board anyway...), it should be best to set the RAM to run at DDR2-533. Also some guys here also mention that running at DDR2-667 dual channel on this board is not stable. So I haven't even tried this.
2c) You should be in sync then. CPU at 1066 is because of QDR (266 x 4), and RAM at 533 is because of DDR (266 x 2). So their real FSB is supposed to be at 266 for both, and it makes 1:1 ratio. You can look for the tests around and you can see that actually CPU at 1066 FSB runs faster with DDR2-533 rather than DDR2-667 or even DDR2-800. Not only on this board. Of course if you go up to 1333 FSB CPU then you should use DDR2-667 RAM. (But if eventually you want to go up to 1333 FSB on this board - which is extremely difficult - you should still set the DRAM frequency at DDRII-533 to keep the ratio at 1:1. If you set the DRAM frequency at DDRII-667, in this case, your RAM will go up to DDR2-833, because when you set the DRAM frequency at DDRII-667 the ratio become 4:5)
At CPU FSB 266 (QDR 1066) and DDR2-533, your CPU and RAM are in sync. In case you want to overclock your CPU FSB, your RAM speed goes up as well. e.g. If you want to run the CPU at 290 FSB, your RAM will be at DDR2-580.
As long as it is a DDR2 RAM the board should be able to recognize. But you may want to set the timings manually - at least for DRAM frequency, CAS Latency, tRCD, tRP, tRAS, and command rate. Cases are different for various brands. Some may have different sets of SPD - e.g. at DDR2-533 the RAM automatically runs at 4-4-4-12, at DDR2-800 the RAM automatically runs at 5-5-5-15, etc. While some may only have 1 set of SPD which you may have to set the timings manually to achieve better performance.
Well I am not an expert on these theoretical things too. I also don't know any reference about this. But I would think that, when both CPU and RAM are in the same bandwidth, their communication in between will not have bottleneck. If any side becomes faster, the faster side will need to queue things up to wait for the slower side, and this simply makes things slower. Correct me if I am wrong.
I would like to add that why 1:1 is better is because of Intel's FSB system. If for AMD which uses Hyper Transport and the cpu has integrated memory controller, the case is different. Hyper Transport makes AMD better in memory performance but the settings may be fussy. If you are interested you can study about this.