Mac OS 7.6, because Open Transport is required, has a "sniffer routine" which checks for the presence of defective L2 cache. If defective hardware is discovered, a dialog is displayed informing the user that a hardware issue was detected and repairs are necessary. The required repairs are covered under the Apple Repair Extension Program.
For more information see Technical Information Library article, "Macintosh 5200/5300/6200/6300: Using Open Transport".