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Changing CAS latency & Buying RAM

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Anonymous
March 24, 2011 3:27:40 PM

Specs:
Intel Core i7 860 @ 2.80GHz
ASUS P7P55D-E Socket-1156 (16GB RAM max!)
4GB RAM Corsair Dominator (CMD4GX3M2A1600C8)
2x 640GB Western Digital Caviar Black
ATI Radeon HD 5850
PSU 750W
Windows 7 Ultimate 64-bit SP1

Hi!
I’ve got two things I tried to solve myself, but well read on:p 


1. Change CAS latency on my current RAM.
2. Buy additional RAM 2x2, but I prefer 4x4.


The current RAM I got now runs 1600MHz at CAS Latency of 8-8-8-24 (1.65v), at least on paper. Because on Piriform Speccy it says: 668MHz (9-9-9-24). Is there a way I can go to BIOS and change it? I read something about XMP Profile if I select that it will change automatically to 8-8-8-24 if I’m not misunderstood?

If it’s possible then when browsing for additional RAM I have to make sure that they also are at CL8 on paper?
Hope you guys can help me out!

Hope my English made any sense.

Peace.

a b } Memory
March 24, 2011 10:42:49 PM

I'll try to explain how this works.

Your RAM has built-in settings, instructions that your motherboard can (hopefully) read. These instructions include frequency, timings (latency) and voltage. One of these settings is called XMP, but it is not normally the default.

So yes, you should be able to activate the XMP without digging too far into the BIOS.

It can be hard to discover the timings on many retail sites. Here in the US newegg usually has them... here is your RAM:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Now, if you add a second set of this RAM to your motherboard it may not run at the CL8 you are hoping for. This is because having 4 sticks of RAM is harder for your motherboard than 2. Usually to get the 4 sticks to work you have to manually adjust things to find settings that will be stable.

So, if you want to have 8GB, I recommend you buy a new 2x4GB kit.

Don't worry too much about timings though, they don't actually make a big difference in the speed of your computer, just a small one.

When your program says 668Mhz, it really means 1336Mhz. I know that is a bit confusing but many programs report the RAM speed that way. DDR means Double Data Rate, so in this case you double the stated speed... 668x2 is really 1336.

March 25, 2011 4:56:08 AM

Proximon said:
I'll try to explain how this works.

Your RAM has built-in settings, instructions that your motherboard can (hopefully) read. These instructions include frequency, timings (latency) and voltage. One of these settings is called XMP, but it is not normally the default.

So yes, you should be able to activate the XMP without digging too far into the BIOS.

It can be hard to discover the timings on many retail sites. Here in the US newegg usually has them... here is your RAM:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Now, if you add a second set of this RAM to your motherboard it may not run at the CL8 you are hoping for. This is because having 4 sticks of RAM is harder for your motherboard than 2. Usually to get the 4 sticks to work you have to manually adjust things to find settings that will be stable.

So, if you want to have 8GB, I recommend you buy a new 2x4GB kit.

Don't worry too much about timings though, they don't actually make a big difference in the speed of your computer, just a small one.

When your program says 668Mhz, it really means 1336Mhz. I know that is a bit confusing but many programs report the RAM speed that way. DDR means Double Data Rate, so in this case you double the stated speed... 668x2 is really 1336.


you are saying that whenever all four slots of ram are filled, memory setting are to be manually adjusted, this doesn't make sense to me. i mean isn't it a lame job on part of the motherboard manufacturer that it cannot handle four sticks of ram on its own a manual intrervention is required to get the workable setting.

ASUS, Gigabyte they are such huge names in motherboard industry they cant even resolve this minor issue? how is this possible :pfff: 
Related resources
March 25, 2011 5:05:14 AM

Not that having 4 sticks of RAM makes the system unstable, just that it may not be stable at the RAMs specified timings. at motherboard stock settings however, the RAM will run fine.
a b } Memory
March 25, 2011 5:38:44 AM

Well, I did say I would "try" to explain it :) 

Yes, the RAM is more likely to run in 4 slots at the more relaxed timings and speed.
March 25, 2011 5:59:36 AM

Guys let me get this straight. if i am building a new rig and i bought 8GB ram(4 sticks of 2GB) and i install them by default they would not run fine and a i have to relax latency timing in order to get them to work
March 25, 2011 9:05:08 AM

No. But if it were rated for a higher setup, it may not run at THAT speed.

since ram with certain timings requires delving into the BIOS to actually hit those speeds. And are only guaranteed for those speeds when used as a kit.
Anonymous
March 25, 2011 9:39:22 AM

Proximon said:
I'll try to explain how this works.

Your RAM has built-in settings, instructions that your motherboard can (hopefully) read. These instructions include frequency, timings (latency) and voltage. One of these settings is called XMP, but it is not normally the default.

So yes, you should be able to activate the XMP without digging too far into the BIOS.

It can be hard to discover the timings on many retail sites. Here in the US newegg usually has them... here is your RAM:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Now, if you add a second set of this RAM to your motherboard it may not run at the CL8 you are hoping for. This is because having 4 sticks of RAM is harder for your motherboard than 2. Usually to get the 4 sticks to work you have to manually adjust things to find settings that will be stable.

So, if you want to have 8GB, I recommend you buy a new 2x4GB kit.

Don't worry too much about timings though, they don't actually make a big difference in the speed of your computer, just a small one.

When your program says 668Mhz, it really means 1336Mhz. I know that is a bit confusing but many programs report the RAM speed that way. DDR means Double Data Rate, so in this case you double the stated speed... 668x2 is really 1336.


Thanks for replying!

I was kind of hoping slamming additional RAM (2x4GB) so I had 12GB in total:p 

Since I live in Denmark, I'm browsing in Danish webshops and It is possible for me to filter search RAM via CAS, but the voltage might be different.
I found these tho: http://www.corsair.com/vengeance-8gb-dual-channel-ddr3-...

Again thanks for replying :) 
a b } Memory
March 25, 2011 9:45:23 AM

Yep, and when you buy a 4-stick kit the manufacturer has already adjusted things so that it will work (hopefully). The real problem comes from buying two 2-stick kits and expecting them to run at advertized speeds without adjustments, you see?

Your original question made it sound like you wanted to add more RAM, pairing it with your existing RAM, and want all 4 sticks to run at CL8. IF you can pull that off you will likely need identical RAM from Corsair.


Anonymous
March 25, 2011 10:39:06 AM

Proximon said:
Yep, and when you buy a 4-stick kit the manufacturer has already adjusted things so that it will work (hopefully). The real problem comes from buying two 2-stick kits and expecting them to run at advertized speeds without adjustments, you see?

Your original question made it sound like you wanted to add more RAM, pairing it with your existing RAM, and want all 4 sticks to run at CL8. IF you can pull that off you will likely need identical RAM from Corsair.



Okay cool, I think I can find the EXACT same RAM model, 2x2 so if I do that there shouldn't be a problem I guess? Even tho all 4 slots are filled, they are the same kind of like a kit.
a b } Memory
March 25, 2011 1:32:58 PM

neo700 said:
Guys let me get this straight. if i am building a new rig and i bought 8GB ram(4 sticks of 2GB) and i install them by default they would not run fine and a i have to relax latency timing in order to get them to work


Not exactly. On the 1156 / 1366 platform, to overclock, we generally adjust BCLK. At a BCLK of 133, I have almost never had a problem with filling all slots and getting them to run at published CAS latencies. The one instances where I did, I had Corsair RAM in two slots and tried adding GSkill to the other two (couldn't find matching Corsairs). This wasn't stable even at stock settings. Bought 2 more GSkills and removed the Corsairs but I machine now only runs at stock settings with reduced CAS timings. It was a "stopgap" measure for my youngest son's box, intended to give an old box a few more months of life with a RAM / GFX upgrade. It's being replaced as soon as B3 version of desired board arrives and Vertex 3 drops.

On machines overclocked to 167, 180, 200 BCLKs and published CAS latencies that ran stable at these settings, when adding a 2nd set of modules to fill the slots, I have oft had to reduce CAS in order to keep the OC stable. Not always but about 40% of the time. Have better luck with Mushkin / Corsair here but my sampling is probably to small (100 builds or so) to form a "rule of thumb".
Anonymous
March 26, 2011 8:00:09 PM

JackNaylorPE said:
Not exactly. On the 1156 / 1366 platform, to overclock, we generally adjust BCLK. At a BCLK of 133, I have almost never had a problem with filling all slots and getting them to run at published CAS latencies. The one instances where I did, I had Corsair RAM in two slots and tried adding GSkill to the other two (couldn't find matching Corsairs). This wasn't stable even at stock settings. Bought 2 more GSkills and removed the Corsairs but I machine now only runs at stock settings with reduced CAS timings. It was a "stopgap" measure for my youngest son's box, intended to give an old box a few more months of life with a RAM / GFX upgrade. It's being replaced as soon as B3 version of desired board arrives and Vertex 3 drops.

On machines overclocked to 167, 180, 200 BCLKs and published CAS latencies that ran stable at these settings, when adding a 2nd set of modules to fill the slots, I have oft had to reduce CAS in order to keep the OC stable. Not always but about 40% of the time. Have better luck with Mushkin / Corsair here but my sampling is probably to small (100 builds or so) to form a "rule of thumb".


In other words, if I purchased the very same model of RAM I got in my rig, I would be fine? (4 slots filled)


March 28, 2011 4:47:40 AM

JackNaylorPE said:
Not exactly. On the 1156 / 1366 platform, to overclock, we generally adjust BCLK. At a BCLK of 133, I have almost never had a problem with filling all slots and getting them to run at published CAS latencies. The one instances where I did, I had Corsair RAM in two slots and tried adding GSkill to the other two (couldn't find matching Corsairs). This wasn't stable even at stock settings. Bought 2 more GSkills and removed the Corsairs but I machine now only runs at stock settings with reduced CAS timings. It was a "stopgap" measure for my youngest son's box, intended to give an old box a few more months of life with a RAM / GFX upgrade. It's being replaced as soon as B3 version of desired board arrives and Vertex 3 drops.

On machines overclocked to 167, 180, 200 BCLKs and published CAS latencies that ran stable at these settings, when adding a 2nd set of modules to fill the slots, I have oft had to reduce CAS in order to keep the OC stable. Not always but about 40% of the time. Have better luck with Mushkin / Corsair here but my sampling is probably to small (100 builds or so) to form a "rule of thumb".


Thanks alot jack for clearing this up
!