Replacing the motherboard

Josh Bytes

Today I listened to GeekNights "Buying a new computer" podcast and after researching a little bit on the internet. I would like to replace my motherboard because my existing motherboard does not have a AGP or PCI Express slots. I want to do this so I can buy a new video card. The video card I have now is a old 9250 Radeon PCI.

The CPU doesn't need to be replaced at least I don't think it does. It's a 3Ghz Intel HT processor. My hard drive is a Ultra ATA 200 Gig.

Here is the link to the board I'm thinking about buying.

Newegg Motherboard

I've never replaced a motherboard before. But I'm pretty sure I can do this. Is there anything I should know before doing this?

Andrew

Have you checked what RAM your current motherboard uses? If it so old that it has no AGP or PCI-E slots, you will probably have to buy new RAM (i.e your computer takes 184-pin DDR SDRAM where as the one you have listed takes 240-pin DDR2 SDRAM). Also make sure your RAM runs at the required clock speed, 166 MHz for the one you have listed.

Josh Bytes

I hadn't thought about the number of pins for the memory. My memory is PC2-3200 DDR2 and I'm pretty sure it's 184-pin not 240-pin. How do you determine the clock speed for the memory?

Andrew

Read through this article. Check the charts in standard specifications.

Apreche

When you look at the specifications for a motherboard, it tells you which memory and processors you can put in it.

Josh Bytes

Okay I think I got it. But I would like to make sure I do got it. I have a HP computer and I went to HP and found the type of motherboard I have.

Motherboard Specs

* Dual-channel memory architecture
* 4 x 240-pin DIMM sockets support unbuffered non-ECC 4 GB 533/400 MHZ DDR2 memory modules
* Maximum HP/Compaq approved memory is 4 GB*

Then I went to crucial downloaded their program that checks what type of memory you have. The memory I have installed is DDR2 PC2-3200. Which are two sticks of 256MB. Crucial says the memory slots can hold DDR2 PC2-4200 with a maximum of 1GB per slot. So does that mean that memory beyond DDR2 PC2-4200 is faster? And I can't use that memory because my board only support memory speeds of 533/400? One last thing Crucial says I have to install my memory in pairs, why?

Forgot to add on Newegg when I'm looking at motherboards the Memory Standard is the speed of the memory right? And not the I guess model numbers ex. DDR2 PC2-3200?

Apreche

This used to be a lot simpler in the olden days. Let me try to explain using my old crappy computer because it is simpler.

My old crap computer had a 450mhz CPU. Every second the clock in the cpu would tick 450 million times. The motherboard supported bus speeds up to 133mhz. My CPU could only handle 100mhz bus speed, so that is what I set it at. Therefore, I set the multiplier to x4.5. 4.5 times 100mhz bus speed equals 450mhz CPU clock speed. Math for the win!

So this bus speed is the speed at which the CPU communicates with the RAM across the motherboard. At 100mhz the clock on that bus would tick 100 million times per second. In order to have this work I needed PC100 RAM. I could have installed PC133 RAM, but it wouldn't have made the computer any faster because the bus speed was 100mhz.

Ok, so now let's look at the desktop computer I'm using right now. The bus speed is 200mhz. The multiplier is x9. 9 * 200mhz = 1.8Ghz CPU. The RAM in this computer is two sticks. Each stick is 256MB of DDR400 RAM. That's 512MB of DDR400 total. 400 you say? Shouldn't it be 200? No, the reason is DDR. DDR is dual data rate. Because of DDR the speed of the memory is 2x the bus speed. DDR is awesome.

But wait, there's more. You have to worry about dual-channel. Most motherboards these day support dual-channel. Dual-channel is a feature that will help you a lot. I won't go into details, but trust me. You want dual-channel enabled. When your computer starts, the motherboard looks at the RAM and decides if it can enable dual-channel. If it enables it, it will usually say so on the boot screen. Motherboards will only enable the dual channel if you have a pair of RAM sticks. That's why I got two 256MB sticks instead of one 512MB stick. It's actually faster to have two sticks because that allows dual-channel to enable.

Lastly, every motherboard is different. For example, my motherboard has three holes for memory. I only use two of the holes. The instructions for the motherboard say that it only supports DDR400 with two sticks. If I want to put in more memory, I need to get two new sticks to replace the ones I've got. If I stick a third stick in there, it will slow down the DDR to 333 instead of 400. It might also cause dual-channel to be disabled.

Basically, you choose your motherboard. Then you choose a CPU that works with that motherboard. Then, you decide how much RAM you want. Lastly, you figure out how you can get that much RAM into your computer while also making it fast as possible. Most of the time these days you just figure out the fastest speed of the RAM that your computer will take and get two sticks that are each half the size of what you need. This is why on Newegg you will see memory listed at 2G and also 2G(1Gx2). 1Gx2 means they are actually selling you two 1 gigabyte sticks that come together in a pair. Pairs are good, just make sure they don't charge you more than it costs to buy the same two sticks individually.

And that's how that works.

Josh Bytes

My head is spinning. But I think I got it. As for setting the multiplier. I didn't know I had to do such a thing to get the CPU to work with the motherboard. I assume that's something you can do in BIOS so it shouldn't be to hard to work out. Thanks for the short lesson on how memory works.