Apple has now provided a statement to MacInTouch in which they say that the 4.1.7 and 4.1.8 firmware updates (see "Avoid Current Firmware Updates" in TidBITS 574) incorporate a new check that validates whether installed RAM is compatible to address random crashes and overall stability issues. The firmware update ignores DIMMs that either don’t meet Apple’s specification or that the update can’t identify as compatible. Of course, this raises the question of why Apple didn’t provide some warning in the firmware update about the possible consequences or why the firmware update doesn’t test the DIMMs before installing.
Glenn Anderson, author of Eudora Internet Mail Server, has stepped up to the challenge with DIMMCheck, a free utility you can run (in Mac OS 9) to see if your DIMMs are likely to fail Apple’s newly enforced specifications. DIMMCheck is only a 4K download, and running it provides a text dump of information about your DIMMs. If problems are found, it encourages you to send the results to [email protected] so Glenn can continue to analyze the problem and – hopefully – provide a utility that can reprogram the offending DIMMs’ Serial Presence Detect EEPROMs so they work again.
So if you wish to run the 4.1.7/4.1.8 firmware updates (which Apple certainly implies provide significant improvements), be sure to check with DIMMCheck before doing so. If your DIMMs fail, send Glenn the results and hold off on the update unless you don’t need the extra RAM. If your DIMMs pass, it’s probably safe to update your firmware. You can download the firmware updates from Apple’s Web site or get them via the Software Update control panel, but note that the firmware updates on the Mac OS 9.1 CD-ROM that comes with Mac OS X are older versions that don’t suffer this problem. We mistakenly said in "Out of the Box: Installing Mac OS X" in TidBITS 574 that you shouldn’t run these firmware updates; that’s a mistake, and we’d encourage anyone installing Mac OS X to run at least the older firmware updates on the Mac OS 9.1 CD-ROM beforehand.
If you’re in the unenviable position of having the firmware updates already disable some of your DIMMs, your best bet right now is to contact the vendor from whom you purchased the RAM. Most of them, according to a Ramseeker survey, are accepting returned DIMMs. They either replace the DIMMs or reprogram the EEPROMs for you. Several people have reported success with test copies of Glenn Anderson’s utility for reprogramming the DIMMs, but there’s no telling when he’ll have enough information to release to the general public. No matter what, Glenn deserves accolades for his work on this problem, in contrast with Apple, whose release of an update that could disable hardware without warning was negligent in the extreme.