This is not the chip that people hoped it would be. AMD's 40MHz 386 ran very well and was quite fast for a 386 because the front-side-bus (FSB) did it's job at 40MHz as well. The 486 model, however, was usually plugged into a normal motherboard with Vesa Local Bus (VLB) slots. These slots ran fine at 25MHz or 33MHz but often caused problems when running at 40MHz or even 50MHz. Because of this the 40MHz part was less common.