Unfortunately, while SLI was quite popular, it was very pricey and took up two PCI slots for 3D only. You then needed an extra available slot (PCI or AGP) for a 2D card.
The second attempt at providing a dual process for rendering a 3D image came from an unlikely source, the software and sometimes hardware engineering company known as Metabyte.
Metabyte's solution was to pair an AGP accelerator with a PCI accelerator that were both matched together from the card's manufacturer, to simultaneously render individual halves of the on screen 3D image.
This PGC or "Parallel Graphics Configuration" solution used Metabyte's exclusively developed drivers to not only link the two cards together, but to also have them divvy up the on screen image processing into two distinct halves, thereby allowing the two cards to work together towards the same goal.