Intel Core i7 920 - Memory Speed Confusion

[masop]

Good afternoon. I am so sick of the nonsense involving processors these days and the dozens of speeds of memory available. There is no clear consensus on what memory is standard, and what memory one needs to buy to get full factory, non-overclocking performance for any given processor. Most motherboards I've seen lately advertise and state "standard memory speeds supported" that don't match the defaults of most processors. What's up with that?

With this in mind, my question is, what is the "default" or "standard" memory type for a Core i7 920 processor? Is it the same as a 965? I have zero interest in overclocking. I just want a correctly paired processor and set of 6GB of memory (triple channel mode) to go with a Gigabyte GA-X58A-U3DR board. All I am positive of is the processor officially supports DDR3-800 and DDR3-1066 memory. That is stated all over the internet, but then there is 1333, 1600 and 2000 and above out there to choose from and so many sources state to get DDR3-1600 or DDR3-2000 memory.

Again, I want a factory default, native, non-overclocked i7 920 system. What memory is required to achieve this? Please advise. Thanks in advance.

-- MaSoP

As a side note, I'm aware the new X58 boards reportedly support the upcoming i9 gulftown processors. I've got no idea so far if the memory would be the same or would have to be faster than what a 920 would use as default in order to maximize a gulftown processor, minus oc'ing.

 

[branflakes71]

The confusing reality is, as was true even with single-core processors, there can be a variety of memory speeds.

In the case of the i7-9xx series, yes, 800 will work, but might be a bottleneck issue in some programs.

I've had 1066 and 1333 in my i7-920 system without issues. I have a slight overclock, and the 1066 couldn't handle that.

I recommend 1066 as your minimum, but 1600 is best to make sure your memory doesn't slow you down, even at default settings.

I don't know the official numbers on Gulftown, but assume at least 1066; higher settings probably being a better choice.

 

[enzo matrix]

Honestly worry about ram the least. Well, maybe not the least. Make sure you get something decent. Get some DDR3 1066 or 1333 or 1600 whatever is the least expensive. The only ones who worry about speed that much are enthusiasts who want to squeak that extra bit of speed from their system. The timings can get confusing. With high timings 1600 can perform worse than 1333 at lower timings. Don't worry about them and just get the cheapest 1333 or 1600 you can get. I agreee with branflakes71 with the exception that "bottleneck" is an overused term and often used not in the right context.

 

[thebski]

Memory speed is something that is very misunderstood about the i7 9XX processors. I have a 920 myself and I've been playing with overclocking and doing some pretty heavy research.

The way I understand it is this: There is a number called BCLK (base frequency) that is coupled with 4 multipliers to determine the CPU frequency, Uncore frequency (built-in North Bridge), DDR3 SDRAM frequency, and QPI frequency.

For example, a totally stock i7 920 system is set up like this:

BCLK = 133 (Same of all 9XX CPU's)

CPU Frequency = BCLK x CPU Multiplier = 133 x 20 = 2.67 GHz

Uncore Frequency = BCLK x Uncore Multiplier = 133 x 16 = 2.13 GHz

DDR3 Frequency = BCLK x DDR3 Multiplier = 133 x 8 = 1067 MHz

QPI Frequency = BCLK x QPI Multiplier = 133 x 18 = 2.4 GHz

The thing to take from this is that your memory will ALWAYS be clocked at 1067 MHz in a stone cold stock system. It doesn't matter if you buy 2000 MHz memory. It will be running at 1067 out of the box. Now, if you buy 1333 memory, the simple thing to do is bump your DDR3 Multiplier up to 10 and that makes your memory actually run at BCLK (133) x DDR3 Mult.(10) = 1333 MHz.

If you buy 1600 memory (like mine) you must up the multiplier to 12 to get 1600. Mine is different because I overclocked my whole system by moving the BCLK to 190. That automatically made my memory run at 190 x 8 = 1520. Technically my memory is underclocked from what it is rated at, but theres no way it would be stable at 1900 which would be the next step at a 10 multiplier (multipliers always go by 2's).

This is my general understanding of memory speed on the Core i7 9XX. If I'm wrong hopefully one of the experts will correct me, but my system is highly overclocked and running like a champ. It was my first attempt at an OC.

Hope this helps.

 

[masop]

Memory speed is something that is very misunderstood about the i7 9XX processors. I have a 920 myself and I've been playing with overclocking and doing some pretty heavy research.

The way I understand it is this: There is a number called BCLK (base frequency) that is coupled with 4 multipliers to determine the CPU frequency, Uncore frequency (built-in North Bridge), DDR3 SDRAM frequency, and QPI frequency.

For example, a totally stock i7 920 system is set up like this:

BCLK = 133 (Same of all 9XX CPU's)

CPU Frequency = BCLK x CPU Multiplier = 133 x 20 = 2.67 GHz

Uncore Frequency = BCLK x Uncore Multiplier = 133 x 16 = 2.13 GHz

DDR3 Frequency = BCLK x DDR3 Multiplier = 133 x 8 = 1067 MHz

QPI Frequency = BCLK x QPI Multiplier = 133 x 18 = 2.4 GHz

The thing to take from this is that your memory will ALWAYS be clocked at 1067 MHz in a stone cold stock system. It doesn't matter if you buy 2000 MHz memory. It will be running at 1067 out of the box. Now, if you buy 1333 memory, the simple thing to do is bump your DDR3 Multiplier up to 10 and that makes your memory actually run at BCLK (133) x DDR3 Mult.(10) = 1333 MHz.

If you buy 1600 memory (like mine) you must up the multiplier to 12 to get 1600. Mine is different because I overclocked my whole system by moving the BCLK to 190. That automatically made my memory run at 190 x 8 = 1520. Technically my memory is underclocked from what it is rated at, but theres no way it would be stable at 1900 which would be the next step at a 10 multiplier (multipliers always go by 2's).

This is my general understanding of memory speed on the Core i7 9XX. If I'm wrong hopefully one of the experts will correct me, but my system is highly overclocked and running like a champ. It was my first attempt at an OC.

Hope this helps.

Thanks for all the tech details. I understand much better now. So, I'd be fine if I simply got DDR3-1066 (PC3-8500) for the 920, but getting 1333 or 1600 simply provides room for overclocking, or perhaps room for newer processors that may have a 1333 or 1600 bus at some point down the road. Thanks again!

-- MaSoP

 

[masop]

Best answer selected by masop.

 

[masop]

Memory speed is something that is very misunderstood about the i7 9XX processors. I have a 920 myself and I've been playing with overclocking and doing some pretty heavy research.

The way I understand it is this: There is a number called BCLK (base frequency) that is coupled with 4 multipliers to determine the CPU frequency, Uncore frequency (built-in North Bridge), DDR3 SDRAM frequency, and QPI frequency.

For example, a totally stock i7 920 system is set up like this:

BCLK = 133 (Same of all 9XX CPU's)

CPU Frequency = BCLK x CPU Multiplier = 133 x 20 = 2.67 GHz

Uncore Frequency = BCLK x Uncore Multiplier = 133 x 16 = 2.13 GHz

DDR3 Frequency = BCLK x DDR3 Multiplier = 133 x 8 = 1067 MHz

QPI Frequency = BCLK x QPI Multiplier = 133 x 18 = 2.4 GHz

The thing to take from this is that your memory will ALWAYS be clocked at 1067 MHz in a stone cold stock system. It doesn't matter if you buy 2000 MHz memory. It will be running at 1067 out of the box. Now, if you buy 1333 memory, the simple thing to do is bump your DDR3 Multiplier up to 10 and that makes your memory actually run at BCLK (133) x DDR3 Mult.(10) = 1333 MHz.

If you buy 1600 memory (like mine) you must up the multiplier to 12 to get 1600. Mine is different because I overclocked my whole system by moving the BCLK to 190. That automatically made my memory run at 190 x 8 = 1520. Technically my memory is underclocked from what it is rated at, but theres no way it would be stable at 1900 which would be the next step at a 10 multiplier (multipliers always go by 2's).

This is my general understanding of memory speed on the Core i7 9XX. If I'm wrong hopefully one of the experts will correct me, but my system is highly overclocked and running like a champ. It was my first attempt at an OC.

Hope this helps.

BTW, should I care much if the memory is rated at CL8 or CL9? I'm aware 6 and 7 is technically "better", but I really don't do things that I would think require pushing every bit of juice out of the system. The most intensive tasks I perform are using quickpar to process/test downloaded archives, especially ISO's and other large multimedia releases. Obviously extracting the contents of large zip and rar files is quite taxing to the hard drives in my system, but I just want to be clear whether that matters much. I occassionally may use a video editing app and I definately watch 1080p bluray titles utilizing the x264 and wmv codecs. I also play games when good titles come out, such as Crysis Warhead, Far Cry 2, Bioshock 2, etc. I've noticed a decent price difference between CL7 and CL8/9, so I'd like to iron this last issue out. Thanks.

-- MaSoP

 

[thebski]

My memory is CL8. I recently just found out that it is automatically set at 9-9-9-24 unless you change it in the bios. Atleast that's how it was for mine. I won't swear that it's that way for everyone though. I wouldn't think timing would make a huge difference, although I've heard very fastly timed RAM can be faster than higher speed RAM. You wouldn't need anymore than 1067 RAM, but if you wanted to buy a little faster it's really simple to just up the multiplier on your memory and get it up to speed. It takes seconds in the bios. It's up to you though. As far as what memory speed and timings mean to real world performance, someone else will have to answer that because I haven't been around enough difference systems to tell.