RDRAM Confusion, please help

[mattuconn]

I have an old Intel VC820 motherboard that supports 100mhz or 133mhz fsb. I have an Intel PIII 1.ghz processor can run at 133mhz fsb. The memory i have is rambus ram that runs at 2x400mhz which i always thought was PC800. I can't get the system to run at 133mhz bus, it stays at 100mhz and is set automatically, tx intel.
My thoughts are that the rdram i have can't run at 133mhz so i was looking to buy ram that can run at 133mhz fsb. I get all confused by modules that say they are RDRAM pc800, RDRAM 800MHz, PC1066 and 1066MHZ. I thought i would need pc1066 but i can find modules that are RDRAM 800MHZ that run at fsb 133mhz. does anyone know the clarification of these?

 

[juin]

The good question does your mothersboards support 133 FSb

Just next to the lab and the bunker you will find the marketing departement.

 

[juin]

The good question does your mothersboards support 133 FSb

Just next to the lab and the bunker you will find the marketing departement.

 

[mattuconn]

The Intel VC820 Motherboard supports both 100mhz fsb and 133 mhz fsb. The PIII 1Ghz processor can do both. I have two 128Mb PC800 Rdram but the system boots using only the 100mhz fsb. What Rdram would i need to run it at 133mhz fsb???
Since this is an intel board it doesn't support forcing a clock or bus multiplier...the board chooses it automatically at boot.

 

[Crashman]

The PIII 1Ghz processor can do both

No. It can do either, or. There were two bus speed versions. The more common version ran at 133x7.5, the less common kind ran at 100x10. If your computer is running at 1000MHz with a 100MHz bus, you can't do 133MHz bus. This is because the multipliers of all PIII CPU's are locked. In other words, if you're running at 10x100, you would have to run at 10x133, aka 1333MHz, in order to use the higher bus speed.

You see, Intel has 3 bus speeds for all their CPU's over the past 8 years. 66MHz, 100MHz, and 133MHz. In order to get 400MHz out of a PII, the CPU ran a multiple, 4x times the 100MHz bus speed. And that 4x mutliple was locked on the CPU. As far as I know, the last CPU to NOT be locked by Intel was the PIII 333.

So getting back to you. If your CPU is a 1000MHz PIII, and it's only runinng at 750MHz, you need to change it to 133MHz bus in order to make it 1000MHz. But Intel boards are made to AUTO DETECT bus speeds, so it's very doubtfull your CPU is running at 750MHz.

Therefore if it's running at 1000MHz and 100MHz bus, you have the 10x multiplier, as previously explained. Since you can't change your multiplier, you can't change your bus speed to 133, because that would force your CPU to run at 1333MHz, and only Crashman can overclock that far, no mear mortals need try!

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