For some reason I assumed that the new Macbook Pro with the Intel GPU and the
Nvidia 330M had both GPUs “integrated” into memory. But actually, it would appear
that the Nvidia GPU looks and acts like a discrete GPU (e.g. integrated == 0 in the
device properties).
Unfortunately, this means that memory mapping on this device does not result
in a performance improvement (except under very strict circumstances and
documented in the Nvidia note on memory mapping). I have tried this and indeed
performance is very bad (as would be expected).
I guess this is a surprise to me. Can anyone else confirm what I have said here
or have I made a mistake ?
(I have also tried ordinary pinned memory and that results in a very modest
improvement of transfer rate).
Thank you,
MW
Yes, the GPU has to be discrete due to changes in the CPU interface on the Core i3/5/7 compared to the older Core 2 CPU. The memory controller has been pulled into the CPU itself to improve performance, but this means that the external chipset no longer has a direct path to system memory. The NVIDIA GPU is hanging off a PCI-express link (also directly connected to the CPU, bypassing the chipset).
Yes, the GPU has to be discrete due to changes in the CPU interface on the Core i3/5/7 compared to the older Core 2 CPU. The memory controller has been pulled into the CPU itself to improve performance, but this means that the external chipset no longer has a direct path to system memory. The NVIDIA GPU is hanging off a PCI-express link (also directly connected to the CPU, bypassing the chipset).