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Selecting memory for 1333 FSB


Digital Dreams

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I have an ASUS P5W64 WS Pro and will soon upgrade the CPU to the quad core QX6850 and it's 1333 FSB....

 

I have four sticks of 8000ul currently running at 800MHz. If I have the numbers right, 1333 FSB on the Intel's is actually 333MHz *4 ??. I guess the DDR makes that 666MHz....hence 5400 memory would do - so my 8000ul (1000MHz) will be very happy & running 'underclocked' !?!?. I can also keep the timings at 8,4,4,9 ??

 

I'm lost in all the numbers....HELP

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Since you're running 4 modules leave the Memory Frequency to Auto. If you experience issue then set the Memory Frequency manually to 667MHZ. If running at 667MHZ you should be able to run at 4-4-3-12@667MHZ 2.2v(or even tighter timines but you will need to test yourself).
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Thanks Ram guy....

 

I seem to have success running 5,4,4,9 (the 1000MHz spec) @2.2v & 666(333) MHz. Memtest shows an increase from 2728 MB/s to 3258 MB/s and passes all tests.....I'm happy for now.

 

Yet this is 1000MHz ram (500 'doubled' ?)....if my bus is 333 (I have no intention of overclocking) can't I triple to 999 ?? (with slacker timings of course). I managed 4343 MB/s for a while @999 before it froze, this shows the system CAN get more at 999....slacker timings than 5,4,4,9 should give me stability and long life ??....

 

Is there any sense in what I'm saying ?

 

I may need to go the 'Dominator' route soon as my ram is needed for another machine and is no longer on sale. Which Dominator could match the 8000ul ?, which if any could beat it ?? (and what would the timings & voltage be ?).

 

Regards & thanks again....

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Based on your system and since you are running the current memory at DDR667, I would suggest the new DHX TwinX4096 2 x 2gb kit of PC6400. With 2 DIMMs instead of 4, you should be able to run the memory at DDR800 and you'll have 2x as much. Also, it will consume less power, run cooler, etc.
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4GB !...not with XP pro...2*1GB will do for now and give air space between the simms...

 

If I can reach 1000MHz with my 8000ul (that's it's spec) I'd want that with Dominator too....not go backwards to 800MHz.

 

How about "Corsair 2GB DDR2 XMS2 Dominator PC2-9136C5 TwinX (2x1GB)" ??. Cheaper than "Corsair 2GB DDR2 XMS2 Dominator PC2-8888C4 TwinX (2x1GB)"?. If rated "1142MHz RAM Speed, CAS 5-5-5-15" I guess I can get closer to the 5,4,4,9 that almost worked with the 8000ul @1000 ???

 

More 8000ul testing to come @1000 (999).

 

Regards

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I seem to have success running 5,4,4,9 (the 1000MHz spec) @2.2v & 666(333) MHz. Memtest shows an increase from 2728 MB/s to 3258 MB/s and passes all tests.....I'm happy for now.

 

Yet this is 1000MHz ram (500 'doubled' ?)....if my bus is 333 (I have no intention of overclocking) can't I triple to 999 ?? (with slacker timings of course). I managed 4343 MB/s for a while @999 before it froze, this shows the system CAN get more at 999....slacker timings than 5,4,4,9 should give me stability and long life ??....

Based on what you have posted here, you are not running your memory at DDR1000. And, that is a very difficult speed to achieve on a 975 based MOBO anyway. The 9136 Dominator is not a good choice at all for this board as the board cannot run the memory at DDR1142.

 

If you are using the settings RAM guy gave you then you have your memory running a DDR 667, not DDR1000. If you use the memory I suggested you can easily run it at DDR800+ since you would have 2 DIMMs instead of 4.

 

Also, even if your 32bit OS cannot fully utilize 4gb of system memory, you will still get 3gb or so which is a 50% increase.

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I agree I'd get 3gb+ with 4, yet see no advantage to that for the time being.

 

You seem to be missing the point re the memory speed...

 

The motherboard IS advertised as 1GHz+ FSB. The 8000ul IS as also 1GHz ram !. I see no reason why I can't run my memory at 999 (333*3) at suitable settings (why do I need to live with 666 ????).

 

I understand that as I have four boards I need to relax the timings, yet expect them and the motherboard to work @1000 as advertised !....

 

I don't expect or plan to run my memory faster than 999MHz yet would expect the top end Dominators to run at this with even faster timings than the lower spec modules.

 

When testing is complete, I may be looking for 2 Dominator sticks to replace the four 8000ul's. Of course I'd expect tighter/faster timings !

 

Regards

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The motherboard IS advertised as 1GHz+ FSB. The 8000ul IS as also 1GHz ram !. I see no reason why I can't run my memory at 999 (333*3) at suitable settings (why do I need to live with 666 ????).

I'm not missing your point, I am just confused. Where are you getting 333 x 3?

 

As far as "living with 666", this is a limitation of the chipset when using 4 DIMMs. 4 DIMMs puts a very heavy load on the chipset. In most cases, you cannot OC the MCH as well with 4 DIMMs as you can with 2. That is why RAM GUY suggested setting the memory to 667.

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333*3 = 999MHz

 

The ratio between bus & memory speed does not have to be 1:1 !. In my bios I can set the memory to DDR999 or whatever and this does not affect the CPU bus speed. So I CAN get 999MHz and have indeed run for a short time at this.

 

On a side note could someone explain how I can run at 999MHz for a while with 5,4,4,9 timings yet not even boot at 999 with a slower 6,5,5,10 ??

 

I understand the chipset could be a limiting factor if using 4 sticks, yet the 8000ul's were not sold as 'PC8000 if no more than two sticks are used together' !. I do feel somewhat 'conned' by that. I baught the four sticks hoping to reach 1GHz one day. Neither was the motherboard sold as '1GHz FSB if only using two sticks of ram' !!.

 

Are you saying I could reach 1GHz with two Dominator sticks ?...

 

Regards

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I am aware that 3 x 333 is 999. Thanks.

 

You have not clearly explained that you are trying to run a memory divider. If you are selecting the bios option to run a 2:3 ratio between the CPU and the memory controller, your memory speed is an X3 ratio of the FSB speed, not the memory speed you actually set.

 

For example if your FSB is 266 (which yours is at stock) you divide it by 2 and you have 133.33 mhz. Then you multiply that by 3, or 133.33 x 3 which would give you a 399.99 mhz memory speed, aka DDR800. To get 1000mhz on the memory using the 2:3 ratio, you will need to OC your FSB to 333mhz which would then give you DDR999. Or, 333.33/2 = 166.66 then 166.66 x 3 = 499.98 memory frequency which would then be DDR 999.96. You can round that to DDR1000. There are other ratios available but I don't think your setup is capable of running them.

 

However, you need to research your 975 chipset. It does not perform well at all with the 2:3 divider. Most 975 boards are VERY hard to tune to get 1000+ on the memory speed. They are MUCH more stable at a 1:1 ratio. And, RAM GUY has already stated that with 4 DIMMs you need to run the memory at 667. It may be possible to reach DDR1000+ with 2 DIMMs of Dominator but, there are no guarantees.

 

Again, all of this is a limitation of the chipset you have, not the memory. If you feel conned by the limit with 4 DIMMs you should contact Intel or ASUS.

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Thanks SpecMike

 

My bus is actually 333 as a default (QX6850 processor).

 

I'm starting to understand this confusing situation now. Of course I feel let down by Asus, my last board had an FSB of 800 and the 8000ul ran happily at that. Now I have a 'advertised' FSB of 1000 I was expecting to run my '1000' ram at that !.

 

I have yet to try 800 again on my new setup. I have achieved an improvement @666 (4,3,3,8 giving 3555MB/s), not bad at all !. I'd still like to reach 1000, maybe the CAS4 'Dominator PC2-8888C4 TwinX (2x1GB)' would push further than what I have....or the 'faster' but cheaper CAS5 'Dominator PC2-9136C5 TwinX (2x1GB)' ??. Are these two actually the same ram chips just tested at a higher clock ?.

 

Regards & thanks for your help....

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Thanks SpecMike

 

My bus is actually 333 as a default (QX6850 processor).

 

I'm starting to understand this confusing situation now. Of course I feel let down by Asus, my last board had an FSB of 800 and the 8000ul ran happily at that. Now I have a 'advertised' FSB of 1000 I was expecting to run my '1000' ram at that !.

You are welcome. I did not realize that you had the QX6850 already....lol.....the math starts all over again.

 

On all the testing I have done on 975 based boards, there is very little advantage to running the dividers. If you want the best performance increase, you really need to OC at a 1:1 ratio. From what I am seeing, using the stock multiplier, the QX6850 CPUs will run a 400-450 on the FSB. So, if you are at 1:1 with the memory, that will be between DDR800 and DDR900. With that in mind, the recommended memory on the configurator is still the best memory for your board.

 

If you want the absolute best of those on the recommendations, get the PC6400C3DF. With this memory you can run at low latencies and at DDR800+. And, if your CPU will OC well (or if you try to run a divider) you can simply loosen the timings and clock the memory even faster than PC6400/DDR800.

 

And, you are correct, the Dominators are currently all based on the same Micron D9 ICs. However, the faster and lower latency parts are parts made with the faster ICs we screen out.

 

Most likely, you'll never get this board past about 1000 or so on the memory. And, there is very little gain on this board to have the memory running faster than the CPU, probably 2-5% at most. Example, CPU at 400+memory at DDR1000 is typically about 2-5% faster in "some" tasks than the exact same setup with the CPU at 400+ memory at 400, aka 1:1. So, the 9136 and 8888 parts are not a good buy for you. They will work of course but, you'll need to underclock them to about the same speeds as the PC6400C3 or PC6400C4 so, why spend the extra $$$, right? It's speed you'll never use.

 

If it was my system, I'd still get a set of the 2 x 2gb PC6400 memory. It's at a great price right now and gives you 2x the RAM which is a bit of future proofing if you stay with a 32bit OS for now. Even with a 32 bit OS, you'll have about 3gb of memory as opposed to 2 for a 50% increase in amount. As far as bandwidth (speed) it will clock plenty fast enough to OC your QX6850.

 

If my opinion counts, here's what I would recommend in this order:

1. PC6400 Twin2X4096 DHX, the 2 x 2gb kit, future proof, plenty fast, more RAM.

2. PC8500C5D, a 1066 kit of 2 x 1gb, it's very versatile and will run any speed your MOBO can run, Micron D9s, same as the other Dominators.

3. PC6400C3DF, low latency 2 x 1gb kit, that will OC to 1066+ if you loosen the timings, lower latencies than the C5D, will most likely OC higher than the 1066 but, your board won't.

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