# Laptop RAM upgrade - 266mhz or 533? PC2-4300 or 4200?

I want to upgrade the RAM in a Toshiba Satellite M70 SR3 Laptop. SIW diagnostic software gives me the follwing info about the current RAM: Capacity: 512MB; Type: DDR2 (PC2-4300); Speed: 266Mhz (DDR2 533); Supported Frequencies: 200.0 MHz, 266.7 MHz, 266.7 MHz.

The CPU is an Intel Pentium M 740, and the FSB speed is 532.0 MHz

I've been looking for replacement RAM (2x1GB), but the specs never seem to match exactly.

Is PC2-4300 the same as 4200? I read one forum post that said they're interchangeable. Often the speed on PC2-4300 or 4200 RAM is listed as 533Mhz. Some references say that a listed RAM speed of 266Mhz mneans an "actual" speed of 533Mhz, which is confusing. Is that what the "DDR2 533" in the specs means?

Will I be able to install 533Mhz RAM? Does the fact that the motherboard FSB is 533 Mhz matter?

Any and all replies welcome.

Thanks

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## 1 Answer

PC2-4300 and PC2-4200 are the same thing it just depends on what manufacturer it is from some round up the speed and label it that way.

From Wikipedia

DDR2 SDRAM gives a transfer rate of (memory clock rate) × 2 (for bus clock multiplier) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte).

This means your PC2-4300/4200 are 133MHz(Memory Clock) x 2 = 266MHz(Bus Clock) x 2 = 533MHz(Data Rate) x 64 = 34112(bits transferred) / 8 = 4264

As you see the 4264 is where PC2-4200/4300 come from an why it depends on who is labeling as some round up and some don't. You can see where the other numbers that are confusing you come into the equation as well.

On older PCs the FSB and ram speeds are tied so yes 533Mhz ram works with your computer and faster ram would work as well it would just be clocked down to the right speed.

On newer PCs you can have different memory ratios so you can run the ram faster than the FSB.

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