G5 and RAM

[GigaWire]

So the dual 5 has a FSB of 1Ghz. The RAM it takes is DDR 400, so 800 effective. Now, in order to get the full speed BUS for the dual 2.0 G5, would you actually have to go with RAM that such as PC3700 which is 466, and later upgrade to PC 3900 @ 500 mhz to take full advantage of the 1 ghz bus?

 

[Simon Liquid]

As I understand it, the way they have the RAM set up accounts for this. The RAM is installed in pairs. Each half of the RAM bank operates seperatly, so if you have a 256 MB chip at 400 cycles per second that can read or write twice per cycle in slot 1 and the same in slot 5 (not sure exactly what the arangment is) the machine sees it as a block of 512 MB RAM that can be written to FOUR times per cycle at 400 Mhz. If this is so, this RAM will match system buss speeds up to 1.6 Ghz.

I might be wrong about this, but that's how I interpretted various documents. Anyone know any better?

 

[Billicus]

Re: G5 and RAM

Originally posted by GigaWire
So the dual 5 has a FSB of 1Ghz. The RAM it takes is DDR 400, so 800 effective. Now, in order to get the full speed BUS for the dual 2.0 G5, would you actually have to go with RAM that such as PC3700 which is 466, and later upgrade to PC 3900 @ 500 mhz to take full advantage of the 1 ghz bus?

I don't think you'll be able to put faster types of Ram other than 400 Mhz in the current models of the G5. They will undoubtably release versions in the future that take full advantage of the speed of the front side bus.

 

[adamfilip]

the way i understand it. is that the ram is not runnning syncronously with the bus
so you can have a 1ghz frontside bus and only a max memory speed of 800mhz (2x400)

this way they can keep ramping up clock speed

say 2.5ghz g5 with a 1.25 ghz FSB and still run dual 400mhz ram

they arent linked..the same way that p4's are. but the faster the ram used the better it will be obviously

 

[NNO-Stephen]

Originally posted by adamfilip
the way i understand it. is that the ram is not runnning syncronously with the bus
so you can have a 1ghz frontside bus and only a max memory speed of 800mhz (2x400)

this way they can keep ramping up clock speed

say 2.5ghz g5 with a 1.25 ghz FSB and still run dual 400mhz ram

they arent linked..the same way that p4's are. but the faster the ram used the better it will be obviously

that's pretty much what I was thinking too. next year we should start seeing some good stuff. first year always gets the kinks out and stuff anyway 3.0Ghz!