Memory for 1066 FSB?
Hey guys I am new to the forumz and I have some confusion that needs to be cleared up. What speed of DDR2 memory do I need to buy to take advantage of a 1066 mhz FSB? I have heard that I only need to use DDR2 533 because Intel's FSB are quad pumped. Is that true? And if so can somebody please explain to me why people spend the extra money on DDR2 800? Is it just for upgradeability or does it have an immediate impact on performance. Also, is the faster memory very important for overclocking? I would really appreciate it if somebody cleared this up for me once and for all.
The 1066MHz FSB is the bandwidth the CPU has to communicate with EVERYTHING, from memory, to hard disk, to graphics card, to LAN, and everything else inbetween.
Dual Channel DDR2 @533MHz theoretically has the same bandwidth as the 1066MHz fsb. So theoretically the CPU could saturate its FSB and also max out the memory.
In practice, the CPU needs to access other things too, HDD, gfx card, etc etc.
In practice, other things need to access the RAM too, like using RAM as additional texture memory when the gfx card's vram is full.
Intels 1066MHz fsb runs on a 266MHz clock. As does 533MHz DDR2. For this reason it can be the case that there are slightly lower latencies using 533MHz ram, due to the 1:1 divider.
In practice, unless ultra low latencies are your aim (professional music production maybe?) I'd prefer to run the RAM faster, say a 400MHz clock for DDR2 800.
I guess if you are using a 512mb gfx card then there probably isnt much need for more memory bandwidth than the CPU has FSB bandwidth, but memory controllers rarely perform at 100% of theoretical throughput so it cant hurt.
darkstar782 thanks for the enlightening explanation. You recommend DDR2 800... what about DDR2 667, that seems like it would give me extra memory bandwith at a slightly lower price. Is it worth it though from an upgradability standpoint (or if I want to overclock) to just go for the DDR2 800 memory?
I'd look at the motherboard, maybe 80% of Pentium 4/D/Core2Duo motherboards only support 667 officially. I assume as you are looking at 1066 FSB however that you are likely talking about Core 2 Duo and therefor a high end motherboard, probably a 965P, that probably will support 800.
Are you planning on overclocking? Thats the main reason I suggested DDR2 800 to be honest, on most motherboards if you set the memory to DDR2-667, then with a 1066mhz FSB (266 clock) there is a 4:5 frequency divider to then connect it to the 333mhz clock of the DDR2-667 RAM.
If you then overclock by raising the FSB to say, 300, you raise the memory clock to 375mhz, making for DDR2-750. At this point you'd better be running DDR2-800 modules, or you'll have to set the system to a lowe divider for slower RAM speeds, or loosen the memory timings, or suffer lots of crashes
I've actually just bought some DDR-2 667 myself, I bought 2gigs of CAS3 ram, on the basis that it should run up to about 880 at CAS4 (33% relaxation in timings meaning a 33% increase in clock, hopefully) and was cheaper than DDR2-800 CAS4.
I'm kinda going on and on and round in circles here, but Core 2 Duo seems to do pretty damn well regardless of memory speeds, so if that is your CPU choice than 667 should be fine. If you overclock you can always change the divider (if in the above 300mhz fsb example you changed the bios to DDR2-533 you'd then be running at DDR2-600 speeds, with plenty of headroom) of loosen the timings (DDR2-667 CAS3 *should* be ok at DDR2-800 speeds if run at CAS4) to cope.
Response @ Kloude. From the reviews I have read C2D apppears to be a great overclocker. With luck and a good motherboard, you will most likely be able to get > 1333Mhz OC so I would probably go for DDRII-800 to give yourself some head room. I have seen reviews where the E6600 has been succsefully OC to 4GHz (444*4=1776MhzFSB) on good air cooling so DDRII-800 would be my preference on a low budget. 1066 DDRII woudl be overkill on the E6600 i think. With 800 you will be able to get up too 400*4 = 1600Mhz FSB which will sync 1:1 with the RAM nicely. If you cant get the high OC at least you can always underclock the RAM with tighter timings to keep the 1:1 ratio or just run it async at 800 for a little speed boost. The Corsair XMS2 6400C4 looks like some not to pricey but decent RAM you could use at it can be OC itself to 1066 with loose timings.
Anandtech did a article on how different ram speeds affect performance on a conroe system. Here is a link to the article.
First of all thanks guys for the help, you've cleared a lot of things up for me. I am indeed planning on building a system around a Core 2 Duo, either 6400 or 6600. At this point I'm not sure if I am going to overclock, alhough it is something I've been considering in which case I should probably go with the DDR2 800. You guys mentioned the timings, is it of utmost importance to have ram running at CAS4 or lower if I am going to overclock? The CAS5 DDR2 ram seems to be more in my budget. Would it be better to get DDR2 667 at lower timings or DDR2 800 at looser ones?
Quote:First of all thanks guys for the help, you've cleared a lot of things up for me. I am indeed planning on building a system around a Core 2 Duo, either 6400 or 6600. At this point I'm not sure if I am going to overclock, alhough it is something I've been considering in which case I should probably go with the DDR2 800. You guys mentioned the timings, is it of utmost importance to have ram running at CAS4 or lower if I am going to overclock? The CAS5 DDR2 ram seems to be more in my budget. Would it be better to get DDR2 667 at lower timings or DDR2 800 at looser ones?
Well DDR2 667 with a dual channel mobo would be able to take you to a 1333Mhz FSB wich is pretty fast ! DDR2 800 could take you to 1600Mhz FSB if your mobo and CPU can take it (some Core 2's are already up to this and more !) I would say it depends on what kind of cooling your going to use ? If your going water then yeah I would take the DDR2 800 but I think air is good up to DDR2 667 if your using a good after market cooler ?
I could be wrong here as no chip OC's the same as the next one. <--- OCing disclaimer lol
@ yieldan: I have found that DDR2-667 at lower timings can be easily overclocked to DDR2-800 at looser timings. Of course DDR2-667 is cheaper, hence to me it doesn't make any sense why I should by DDR2-800. You can of course get high quality DDR2-800 and overclock IT, but then it would cost WAY MORE than standard DDR2-667. I, personally, am not prepared to splash out that much on RAM.
@ Calapuso: I've just bought an ASUS P5W DH, so yeah I'll be able to overclock my FSB through the roof 8) . I only plan to OC to 1333Mhz though (for now), which comes together nicely if I run my RAM at 667. I've ordered Corsair TWIN2X2048-5400C4 2GB (2x XMS2 1GB) before I posted here, so I can't really change anything in regards to RAM. However, I know that it will be able to run 800Mhz @ 4-3-3 timings at the very least (can't remember a link). So, I do have a bit of headroom anyway. If I was planing to OC my CPU to the limit that it can take then, yes, I would've bought better RAM. As it stands though, I would rather spend my money on something else. Thanks for your help though!
Here is a good air over clocking cooler !!! Hahaha.... its only 150$ but I want it...
Its a air/peltier cooler with a controller built in so the peltier doesnt run all the time (only when needed) therefor it doesnt have the nasty side effect of condensation !