After Effects System Requirements Multi-frame Rendering Gpu Vram -

The official minimum of 2GB–4GB is rarely sufficient for professional motion graphics work when MFR is active.

Here is what happens on the timeline when you enable MFR: The official minimum of 2GB–4GB is rarely sufficient

When your GPU runs out of VRAM, the system does not crash gracefully. It via the PCIe bus. That pipeline is roughly 10x slower than native VRAM. The official minimum of 2GB–4GB is rarely sufficient