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DDR2 RAM: Better performance with 5GB @ 800MHz or 4GB @ 1066MHz?

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September 25, 2011 4:51:30 PM

My 4-year old system had one of its memory sticks die, so I'm down to just 1GB. The sole remaining 1GB stick is a Corsair XMS2 Dominator (DDR2 PC2-6400 800MHz 4-4-4-12 CAS 4).

My predicament is: I see that the market for DDR2 RAM nowadays offers DDR2 RAM at speeds as fast as PC2-8500 (1066 MHz). I understand that I should not mix RAM speeds, as my system would just "downgrade" every stick to run at the lowest speed stick mounted. So, since I'm going to purchase 4GB of RAM, should I get it in PC-6400 800MHz sticks so that it can play with my 1GB stick, for a total of 5GB? Or, should I chuck my 1GB stick of 800MHz RAM, and opt to run just 4GB, but at the faster PC2-8500 1066GHz?

Motherboard: Asus P5N-E SLI nForce 650i SLI Socket 775 1066MHz, BIOS 1406, nForce driver 15.57
CPU: INTEL Core 2 Duo E6850 3GHz FSB1333MHz 4M LGA775 Retail BX80557E6850 Processor
a c 347 } Memory
September 25, 2011 4:59:16 PM

Welcome to Tom's Forum! :) 

ref P5N-E SLI - http://usa.asus.com/Motherboards/Intel_Socket_775/P5NE_...
4 x DIMM, Max. 8 GB, DDR2 800/667/533 Non-ECC,Un-buffered Memory
Dual Channel memory architecture
*When installing total memory of 4GB capacity or more, Windows 32-bit operation system may only recognize less than 3GB. Hence, a total installed memory of less than 3GB is recommended.

According to ASUS, the limit is DDR2-800 and unless you have a 64-bit OS then you're stuck to 4GB with 3.0GB~3.5GB usable. Further, on DDR2 Dual Channel does help so whatever you get, get a matched-set of 2x__GB; both channels MUST be the same sized and it's best to use 1GB or 2GB per stick sets. For 4GB 2x2GB, and 8GB 4x2GB; 8GB/4-DIMM Slots = Maximum 2GB/DIMM.

Q - What Exact OS?

Windows Memory Limits -> http://msdn.microsoft.com/en-us/library/windows/desktop...(v=vs.85).aspx
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a b } Memory
September 25, 2011 5:09:02 PM

Your memory needs to run in pairs for best performance. Such as 2x2gb sticks or 4x1gb sticks. Not odd numbers.

They also need to be the same voltage, speed and timings if your going to mix it with your current ram.
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September 25, 2011 6:04:32 PM

jaquith said:
Welcome to Tom's Forum! :) 

ref P5N-E SLI - http://usa.asus.com/Motherboards/Intel_Socket_775/P5NE_...
4 x DIMM, Max. 8 GB, DDR2 800/667/533 Non-ECC,Un-buffered Memory
Dual Channel memory architecture
*When installing total memory of 4GB capacity or more, Windows 32-bit operation system may only recognize less than 3GB. Hence, a total installed memory of less than 3GB is recommended.

According to ASUS, the limit is DDR2-800 and unless you have a 64-bit OS then you're stuck to 4GB with 3.0GB~3.5GB usable. Further, on DDR2 Dual Channel does help so whatever you get, get a matched-set of 2x__GB; both channels MUST be the same sized and it's best to use 1GB or 2GB per stick sets. For 4GB 2x2GB, and 8GB 4x2GB; 8GB/4-DIMM Slots = Maximum 2GB/DIMM.

Q - What Exact OS?

Windows Memory Limits -> http://msdn.microsoft.com/en-us/library/windows/desktop...(v=vs.85).aspx


Thanks for the welcome; I've been a lurker at TomsHardware since pre-2005.

I'm going to be running Windows 7 6-bit so I'm not concerned about OS limitations.

I didn't think I was limited to DDR2-800 with my P5N-e SLI for 2 reasons:

1.) I also saw the same ASUS spec that you did, where it seems to imply that DDR2-800 is the maximum that it supports, but as I recall, DDR2-1066 was not readily available at the time of P5N-e's manufacure in 2007, so I just assumed their spec sheet was outdated.
2.) Crucial.com's own website page for the P5N-E SLI motherboard states that it does in fact support PC-8500 (1066MHz) RAM: http://www.crucial.com/upgrade/compatible-memory-for/AS...

That said, at a quick glance at retail websites, it looks like that DDR2-800 RAM models have faster timings than DDR2-1066 ones...so maybe I'll have faster options with DDR2-800 anyway?
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a b } Memory
September 25, 2011 6:38:47 PM

DDR2-800 is the sweet spot. Only if your doing heavy overclocking would 1066 give you any advantage really.

I'd take the 800 with better timings.

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a c 347 } Memory
September 25, 2011 6:45:14 PM

1. If the BIOS has DRAM Frequency -> DDR2-1066MHz then you're good. If not 'maybe' a BIOS upgrade does. And NO it doesn't matter if you have slower RAM installed to 'see' the menu options in the BIOS.

2. Crucial has a lot of errors, and when it comes to ASUS vs Crucial then ASUS wins.

Most DDR2-1066 will/should reduce to DDR2-800 frequency, just manually set the DRAM Frequency, CAS Timings, and DRAM Voltage.
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a b } Memory
September 25, 2011 7:11:17 PM

that ram has a lifetime warranty. aren't you going to send it back ? Don't mix and match. Get same stuff regardless of what you choose. DDR2800 vs 1066...... you'll never see the difference in speed only the difference in price. Run the ram in dual channel and stay away from odd uneven amounts.
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September 26, 2011 1:45:52 AM

geekapproved said:
Your memory needs to run in pairs for best performance. Such as 2x2gb sticks or 4x1gb sticks. Not odd numbers.

They also need to be the same voltage, speed and timings if your going to mix it with your current ram.


The voltage needs to be the same too? That's going to be tough; do you know if there's any flexibility in that?

Some new 800MHz RAM that I'm looking at is rated at 2.0V (Crucial Ballistix BL2KIT25664AA80A). My XMS2 Dominator RAM is rated at 2.1V. Timings are identical at 4-4-4-12. Does that close enough, or would I be setting myself up for constant crashing?
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September 26, 2011 1:48:59 AM

swifty_morgan said:
that ram has a lifetime warranty. aren't you going to send it back ? Don't mix and match. Get same stuff regardless of what you choose. DDR2800 vs 1066...... you'll never see the difference in speed only the difference in price. Run the ram in dual channel and stay away from odd uneven amounts.



I didn't know my XMS2 Dominators had a lifetime warranty; I will definitely invoke the warranty then.

My plan is now going to be to invoke the warranty on my broken 1GB XMS2 Dominator stick, but still buy an addition 4GB of RAM (2x2GB), for a grand total of 6GB (I'm prepping for the game Battlefield 3). For the new RAM I'm considering the Crucial Ballistix BL2KIT25664AA80A ( http://www.newegg.com/Product/Product.aspx?Item=N82E168... )
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October 7, 2011 1:41:14 AM

Best answer selected by pwens.
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