The IBM PGC (1984) was a discrete GPU with 320kB of RAM and slightly over 64kB of ROM.

The EGA (1984) and VGA (1987) could conceivably be considered a GPU although not turning complete. EGA had 64, 128, 192, or 256K and VGA 256K.

The 8514/A (1987) was Turing complete although it had 512kB. The Image Adapter/A (1989) was far more powerful, pretty much the first modern GPU as we know them and came with 1MB expandable to 3MB.