Upgrade 24” iMac video card - ATI Radeon 256MB to NVIDIA GeForce 512MB - Ask Different
Amazon.com: Original Graphics Card for Apple iMac Early 2008 24-Inch A1225 Desktop Computer Core 2 Duo 2.8 MB325LL/A, ATI Radeon HD 2600 Pro GDDR3 256MB, GPU Upgrade Video Cards Replacement Spare Parts : Electronics
Amazon.com: Original GDDR3 512MB Graphics Video Card GPU Replacement for Apple iMac Early 2008 A1225 Core 2 Duo 3.06 MB398LL/A MB398 24-Inch Desktop PC, nVidia GeForce 8800 GS GT GTS, MXM VGA
2010 iMac GPU Upgrade to NVIDIA GTX 765M - YouTube
Refurbished 24-inch iMac Apple M1 Chip with 8‑Core CPU and 7‑Core GPU - Blue - Apple