Plug-in a DDR2 800MHz to a slot that can handle up to 667MHz only

memorymotherboardupgrade

I have an old computer that has an ASUS P5S-MX SE motherboard, and only have a 1GB RAM. So I planned to upgrade the RAM and buy a 2GB RAM. Only DDR2 can be installed in the motherboard. So I looked up on the internet and found a second hand 2GB RAM DDR2.

My only mistake is that I didn't considered before buying was the MHz, and found out that the DDR2 I bought was 800MHz. Knowing that my motherboard can only handle up to 667MHz only.

Question 1:

Is it still gonna work with my motherboard? I'm now planning to remove the 1GB RAM and replace it with my newly bought DDR2 2GB 800MHz.

Question 2:

If it is, are there any disadvantages or cons?

Question 3:

If it is, is it okay to have them both installed in my motherboard? One 1GB DDR2 667MHz and one 2GB DDR2 800MHz? Are there any disadvantages if they are both installed in my motherboard?

Question 4:

If having a 2GB DDR2 800MHz and a 1GB DDR2 667MHz is not compatible. Can I have two 2GB DDR2 800MHz installed, in slots that can only handle up to 667MHz only, in my motherboard? Will it not affect other circuits or power?

Best Answer

The DDR2 RAM can be run at lower frequency without any issue. The motherboard will run the RAM at 667MHz instead of 800MHz and everything will be fine. The disadvantage is that you lose a bit of performance from the lower frequency.

Related Solutions

Can a 800Mhz memory stick be used in a 400Mhz slot

The best way to check for compatible memory options is with Crucial's tool -- CrucialScan.exe

The Crucial System Scanner automatically analyzes your computer memory information and suggests an upgrade that's guaranteed compatible.

It has helped me on multiple old machines (workstations and laptops).
It will also answer your question accurately for your system motherboard capabilities.

For DDR2 PC2-xxxx and the MHz figures look at this DDR2 wikipedia page.

The two things are similar ways to measure almost the same thing.
Look at the Wikipedia table and small print under it.
PC2-5300 ~ 667Mtps ~ 333MHz and,
PC2-6400 ~ 800Mtps ~ 400MHz.
For normal things, either would not make too much of a difference.
If you get a price advantage, PC2-5300 would be fine.

Here is page-2 of a long article on Dual Channel memory discussing these details.

Further on your comments, people quote frequencies differently at times (probably to make life more confusing for the buyer).
There are a lot of other references that explain these terms.
Here is one more link which has these relevant lines after the explanation.

ddr2 400 = 100mhz internal speed = 200mhz external speed = 400mhz DDR = pc2-3200
ddr2 533 = 133mhz internal speed = 266mhz external speed = 533mhz DDR = pc2-4200
ddr2 667 = 166mhz internal speed = 333mhz external speed = 667mhz DDR = pc2-5300
ddr2 800 = 200mhz internal speed = 400mhz external speed = 800mhz DDR = pc2-6400

PC Memory – Can Different RAM Modules Be Mixed?

Possibly.

However, having paired modules (e.g. 2x2GB) will more than likely give you better performance as the memory can run in Dual Channel mode rather than Single Channel. You won't get exactly double the transfer rate as there are overheads involved but it should be close.

The relevant thing to bear in mind is:

Modules rated at different speeds can be run in dual-channel mode, although the motherboard will then run all memory modules at the speed of the slowest module.

Related Question

PC with 2 RAMs of different frequencies (1GB 533MHz + 2GB 667MHz) showing only 2GB RAM