Quote Originally Posted by Ryunosuke View Post
Looking over the VGLeaks diagrams and pages again, I think you might be mistaking a little on the GPU being able to concurrently read and write.

I believe the 'GPU Memory system' portion of the diagram is just to represent the memory allocated for the GPU. I don't think it is meant to suggest that the GPU can read from the DDR3 at 68GB/s and write to the ESRAM at 102GB/s concurrently.

It appears the GPU can either write to this allocated memory at 102GB/s or read from it at 170GB/s but not both concurrently. I believe there is only a single 256-bit memory bus, same as PS4.
If this was the case wouldnt it show a single line with arrows going both ways?

You can only read a 170gb/s as a combination of both memory clients, 102 + 62.

But you can only write back at 102 maximum.
Its all very vague.

All the Move Engine is doing there is moving/copying data between the DDR3 RAM and/or ESRAM. It uses the bandwidth of the DDR3 RAM and/or ESRAM to achieve this; depends on how it is moving/copying the data around.

Yes, it does it in parallel with computation of the GPU but at a slower throughput and at the sacrifice of bandwidth if the memory is being used by the GPU at the time. This doesn't mean or suggest that the GPU can write to the ESRAM and read the DDR3 RAM concurrently.
It can certainly read ESRAM and read DDR3 concurrently.

The 360, can read from GDDR and write concurrently to the EDRAM, thats why its so dam good as a GPU, because it has zero wait states for the memory. Perhaps concurrently is a little of a misnomer, lets just say so dam fast it may as well be concurrent.

It still looks like two separate buss's...

The move engines can move data from EDRAM to EDRAM or DDR to DDR, without messing up the the GPU's own write features to the other.

ie. GPU->EDRAM, separate to GPU->DDR.