While the new Mac Pro features six available PCI Express expansion slots for audio, video capture, storage, networking, and more, the desktop tower is no longer compatible with graphics cards. Instead, graphics processing is handled entirely by the M2 chip, which includes up to a 76-core GPU that can access up to 192GB of unified memory. Apple's hardware engineering chief John Ternus briefly touched on the matter in an interview with Daring Fireball's John Gruber last week, explaining that expandable GPU support for Apple silicon is not something that the company has pursued. "Fundamentally, we've built our architecture around this shared memory model and that optimization, and so it's not entirely clear to me how you'd bring in another GPU…