Question about cpu architecture and the L2 cache

[zmzhang]

I was wondering. If a cpu manufactor removed the L2 cache and placed it on the mb, but it was still running at full speed. Would the manufactor be able to add additional code (Such as support for 64 bit programs?)to the cpu and increase the speed even more? And is it possible to run the L2 cache at full speed while it is on the motherboard?

Thanks

 

[gogeeta13]

Problem is, the lag of having cache on MOBO. When it is onboard, and so close in proximity, it makes it much faster. Electricity does not travel instantaneouly, it does take time..

 

[Rand]

<< And is it possible to run the L2 cache at full speed while it is on the motherboard?

Thanks >>


Possible?
Yes. However I don't even want to think about the cost of SRAM's that could run at over 1GHz, if indeed there are any.
You also have to take into account the latency would be increased very significantly by having the L2 cache on the motherboard. Pure bandwidth is not all that matters.
Also, to use the P4 for an example it's on-die L2 cache has a 256bit datapath, something that would be near impossible to manage with off-die cache.

 

[BurntKooshie]

<< Would the manufactor be able to add additional code (Such as support for 64 bit programs?)to the cpu and increase the speed even more? >>

Cache really has nothing to do with the &quot;bit-ness&quot; of computing -- you could have a 64-bit architecture that has no cache at all (it'd be stupid unless it was in the same vein as the Cray MTA, but possible).

If you want to know more about caches, this might be useful (if a bit on the long, and dense side).

 

[SuperTool]

RC delay too high from Cache to CPU. It's going to be awfully difficult if not impossible to transfer data between these two chips at 1GHZ reliably. Even synchronizing these two would be difficult at these speeds. All this will result in huge latencies, making it not worth it at all. Besides try buying 1 GHZ cache chips

 

[zmzhang]

Ok, thanks everyone. That was exactly what i wanted to know.