G5 and l3 cache

[satanicpoptart]

i just thought about it and realized that the new g5 has no l3 cache, unlike its younger sibling the g4. why is this?

 

[RacerX]

The reason for having the Level 3 cache was to make up for the slow bus speed between the RAM and the processor. In the new G5 systems, this isn't a problem any more. The G5 can transfer more than 6 GB per sec of data between the processor and RAM.

 

[Pengu]

It was only the high frequency G4's with L3 cache anyways. I have a G4 400 (gigabit ethernet) and it has NO L3, but 1Mb of L2 cache (compared to 512k on newer models incl. G5)

 

[satanicpoptart]

id think that a healthy amount of l3 cache would still help the g5, but i guess the cost or size consumption on chip wasnt worth it...

 

[Captain Code]

It doesn't need L3 cache because, like RacerX said, the system bus is fast enough that the CPU can fetch data from the RAM without having to wait for the slow bus like in G4 systems.

L3 cache is only needed to store frequently needed data/instructions so the CPU doesn't have to wait while they are retrieved from main RAM.

L3 cache is quite expensive as well, and if it's not needed, there's no reason to increase the cost of the CPU.

The G4 400 doesn't need any because the CPU is too slow to require data faster than what the system bus can transfer.