alt Hacker NewsWhy did all my x86 onboard iGPU reserve a fixed amount of RAM on boot, inaccessible to the OS? Why do dGPU bring their own VRAM and how to directly manipulate it from the CPU without copying?
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fulafel • today at 7:11 AM
To the first question: blame Windows I guess. But even on older chips, GPU code could access memory allocated on the CPU side so this didn't cap the amount of data your GPGPU code could crunch.
Correct me if I'm wrong, but that reserved memory is for the framebuffer? The iBoot bootloader also reserves some memory for the framebuffer.
dGPUs bring their own VRAM because it's a different type of memory, allowing them to get higher performance than they could with DDR. The M4 Max requires 128GB of LPDDR5X to reach its ~500GB/s bandwidth. The RX Vega 64 had that same bandwidth in 2017 with just 8GB of HBM2.