FSB on the MBP 17 = 800mhz.. so why the 667 ram?

[bbplayer5]

Is there 800mhz DDR you can throw into these?

 

[Eidorian]

There's no reason to get DDR2-800.

 

[rrijkers]

Is there 800mhz DDR you can throw into these?

Thats what i thought too, but i think it are 2 different things...

 

[Eidorian]

Thats what i thought too, but i think it are 2 different things...

RAM speed can be independent of the front side bus speed.

 

[Eluzion]

Based on what I was told, the Santa Rose core doesn't run RAM at 800mhz frequency. The 800mhz advertised is the FSB, which is the northbridge connector with the CPU. So running DDR2 6400 RAM, it would still underclock to 667mhz.

 

[Eidorian]

Based on what I was told, the Santa Rose core doesn't run RAM at 800mhz frequency. The 800mhz advertised is the FSB, which is the northbridge connector with the CPU. So running DDR2 6400 RAM, it would still underclock to 667mhz.

That's right!

 

[Eluzion]

Must be a mobile CPU thing though because every CPU (AMD or Intel) I've used on a desktop runs a 1:1 ratio with the FSB. Either way, no biggy. MBP is still a beast.

 

[Mindflux]

Must be a mobile CPU thing though because every CPU (AMD or Intel) I've used on a desktop runs a 1:1 ratio with the FSB. Either way, no biggy. MBP is still a beast.

You must not have been around a lot of desktops.

I have a slew of 1200 Athlon's at the office that run at a 133Mhz multiplier for CPU clock frequency. The ram? DDR-2100 (266MHz)

 

[Eidorian]

You must not have been around a lot of desktops.

I have a slew of 1200 Athlon's at the office that run at a 133Mhz multiplier for CPU clock frequency. The ram? DDR-2100 (266MHz)

133 MHz double pumped = 266 MHz

Not in actual clock speed though. The RAM still runs at 133 MHz.

 

[Mindflux]

133 MHz double pumped = 266 MHz

Yes,but these Athlon FSB is 133, not 266

 

[Eidorian]

Yes,but these Athlon FSB is 133, not 266

The RAM still runs at 133 MHz.

 

[TheStu]

The RAM still runs at 133 MHz.

That and more and more of the Intel chips that have the shiny new 1333MHz FSBs can run on 800MHz or faster DDR2 (though I think that the actually, the 1333 is DDR3 RAM... but whatever)

 

[Eidorian]

That and more and more of the Intel chips that have the shiny new 1333MHz FSBs can run on 800MHz or faster DDR2 (though I think that the actually, the 1333 is DDR3 RAM... but whatever)

Yeah just thinking about it does give headaches when you now add DDR3 into the mix.

DDR = Memory Clock * 2 (133 MHz = DDR-266 = PC 2100)
DDR2 = Memory Clock * 4 (133 MHz = DDR2-533 = PC2 4200)
DDR3 = Memory Clock * 8 (133 MHz = DDR3-1066 = PC3 8500)

The 1,333 MHz front side bus would be 333 MHz * 4. (quad pumped)