The title might be a bit misleading, so allow me to clarify a bit . If we look at the traditional Intel-architecture and compare it to NUMA-system (like AMD64), the difference are obvious. On Intel, the RAM is attached to the Nortbridge, and each CPU is connected to that nortbridge, and they share the RAM. On AMD-machines, the RAM is connected to the CPU, and each CPU can use other CPU's RAM as well. The northbridge is focused on handling PCIe and other tasks (for the sake of simplicity, I'm assuming a single-chip chipset).
Now, the benefits of the AMD-approach are obvious: The memory-latencies are lower, mem-bandiwdth goes up as number of CPU's increase, and the FSB can be dedicated to other tasks than accessing the RAM. But would there be any benefits if there was some RAM attached to the Northbridge as well?
More details: What if, besides having RAM attached directly to the CPU, the northbridge would also have RAM-banks attached to it? What uses could that RAM serve?
- Texture-cache for the vid-card
- IO-buffer
- Shared RAM for the CPU's
- Some other things I can't think of right now
Yes, the CPU-attached RAM could be used for textures right now. But when doing so, it needs to go through the FSB. And the FSB could be used for other things. And the CPU-attached RAM could be dedicated for the CPU, while the vid-card would have RAM of it's own at it's disposal. I could imagine that the hi-end 3D-folks would love to have few gigs of dedicated texture-RAM at their disposal .
And that RAM could be used by the CPU as well, effectively increasing the mem-bandwidth, when the CPU has it's own RAM at it's disposal, the RAM attached to other CPU's, and the RAM attached to the northbridge. But, OTOH, the northbridge-RAM could be dedicated to strictly other uses, like textures and IO. In that case, could it run at different speed than the CPU-attached RAM does, or would there be timing-issues?
Would this make any sense, or am I talking BS? I would guess that normal PC's wouldn't really benefit, but what about workstations?
Now, the benefits of the AMD-approach are obvious: The memory-latencies are lower, mem-bandiwdth goes up as number of CPU's increase, and the FSB can be dedicated to other tasks than accessing the RAM. But would there be any benefits if there was some RAM attached to the Northbridge as well?
More details: What if, besides having RAM attached directly to the CPU, the northbridge would also have RAM-banks attached to it? What uses could that RAM serve?
- Texture-cache for the vid-card
- IO-buffer
- Shared RAM for the CPU's
- Some other things I can't think of right now
Yes, the CPU-attached RAM could be used for textures right now. But when doing so, it needs to go through the FSB. And the FSB could be used for other things. And the CPU-attached RAM could be dedicated for the CPU, while the vid-card would have RAM of it's own at it's disposal. I could imagine that the hi-end 3D-folks would love to have few gigs of dedicated texture-RAM at their disposal .
And that RAM could be used by the CPU as well, effectively increasing the mem-bandwidth, when the CPU has it's own RAM at it's disposal, the RAM attached to other CPU's, and the RAM attached to the northbridge. But, OTOH, the northbridge-RAM could be dedicated to strictly other uses, like textures and IO. In that case, could it run at different speed than the CPU-attached RAM does, or would there be timing-issues?
Would this make any sense, or am I talking BS? I would guess that normal PC's wouldn't really benefit, but what about workstations?