RAM Upgrading - Different Speeds


My collegue and I are both having a disagreement regarding RAM.

I have a laptop with 1GB of RAM - I have bought a 2GB RAM module as well.

1GB 333MHz
2GB 667MHz

I personally think that as the 1GB would bring both modules down to 333MHz that we may as well take the 1GB stick out, so we have the following:

2GB running at 667MHz

Rather than:

3GB running at 333MHz

Can you guys please give us your input as I'd really like to prove him wrong!

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helpfinderIT ConsultantCommented:
the speed will be as the lowest speed (MHz) is, in this case 333 MHz
tetraukAuthor Commented:
the speed will be as the lowest speed (MHz) is, in this case 333 MHz

Yes - so would you recommend 2GB 667MHz or 3GB 333MHz?
☠ MASQ ☠Commented:
What is the FSB speed of the systemboard? If the laptop was provided with RAM already running at the fastest speed the board can handle then your 2GB stick won't run faster than 333 MHz anyway.
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tetraukAuthor Commented:
What is the FSB speed of the systemboard? If the laptop was provided with RAM already running at the fastest speed the board can handle then your 2GB stick won't run faster than 333 MHz anyway.

The FSB is 667MHz.

Out of principal, which is best?

3GB of RAM running at 333MHz

or 2GB of RAM running at 667MHz?
That would actually depend on whether the applications running on the laptop use a lot of RAM or not.  If the machine is typically running with a lot of applications simultaneously or with applications that require a lot of RAM, then 3GB is better, but if the applications need to run as fast as possible, then 2GB at higher speed is better.  It is a question of what is constraining the machine's performance, and that depends on the applications.
2GB running at twice the speed as 3GB would be the better choice, in my opinion.  Even though it isn't a processor, you can think of it that way when it comes to speed.  Which is better a single processor running at 3 Ghz or a dual core running at 2 Ghz?
Gary CaseRetiredCommented:
There's no simple answer to your question.

First, as Masqueraid noted, the FSB of your system, the system bus speed (not the same as the FSB),  and the specific CPU that's installed will determine the maximum speed installed RAM can run at.    I'd do a simple test:

=>  Install CPU-Z  [Free download here:  http://www.cpuid.com/softwares/cpu-z.html
      (be sure to get the appropriate version -- 32 or 64 bit)

=>  With JUST the 1GB module installed, run CPU-Z and see what's shown on the Memory tab for the DRAM frequency  (Note the SPD tab will show the capabilities of the RAM, but the Memory tab shows the speed it's actually operating at)

=>  With JUST the 2GB module installed, run CPU-Z and see what speed it's running at.

... that will tell you if you system can indeed utilize the higher speed memory's increased bandwidth.

If not, then obviously you should install all 3GB.

If it does make a difference, then you need to consider two other factors:

(1)  Does the system support dual channel RAM?   [Note that this is shown on the CPU-Z Memory tab -- as well as the mode of the dual channel operation]     If it does, then the bandwidth of RAM transfers is doubled -- but you'll only get this benefit with two installed modules.    Note that with modules of difference size, you'll not get the maximum symmetric dual channel mode;  but with most chipsets you'll still get some benefit from the asymmetric mode.    This will offset a lot of the speed difference -- as the real comparison then becomes 2GB operating at a higher speed but in single channel mode vs. 3GB operating in asymmetric dual channel mode.    To really ascertain the difference, I'd run Memtest 86+ [http://www.memtest.org/ ] with both configurations and note the indicated memory bandwidth.

(2)  What application mix are you running (as Callandor asked above)?    If you are running a lot of open windows and/or very memory intensive programs, you'll probably benefit from the 3GB a lot more than you would from faster RAM.    Remember that every page fault slows things down by a factor of over 1,000 while the pages are swapped to disk ... and you'll have a lot more page faults with 2GB than with 3GB.     These are transparent to you unless you get so many that the system is clearly "sluggish" -- but they do happen.

Bottom Line:   Without some experimentation, I can't say for sure which configuration is better, but in most cases -- and certainly if it's a dual channel capable chipset -- I'd go with the 3GB configuration.

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tetraukAuthor Commented:
ok 1 for, 1 against...anyone else?
I won't speak about technical stuff as the other comments were good and complete.
But on my personnal experience I wouldn't mix RAM with different speed.

Some laptop have trouble to manage mix of speed and some even had blue screens and unexpected reboot.

In your case I would prefer to keep 2 GO and losing 1GO that having an unstable laptop.
Gary CaseRetiredCommented:
It's not a question of "for" or "against".     To determine which is better, you need to confirm whether or not the higher speed module actually runs faster;  whether the chipset supports dual channel;  and finally whether your particular set mix of applications is generating a significant number of page faults with only 2GB installed.     I outlined how to do all that above.
Gary and I are essentially in agreement, so I don't see how the count is "1 for, 1 against".  You might also consider how many questions have been answered by each "expert" - opinions are not always equal, like votes.
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