Perhaps the most essential utility that fell prey to compatibility problems when Mac OS 9 came out was Connectix’s RAM Doubler 8, which replaces Apple’s built-in virtual memory scheme with alternative methods of increasing the amount of memory available to applications. It does this by first reclaiming unused memory from other applications, then by compressing memory in use so it takes less space, and finally by swapping the contents of memory out to disk. (See "Free RAM Doubler 8 Update" in TidBITS 439 and "RAM Doubler 2" in TidBITS 351 for more details.) Connectix has now released a free update to RAM Doubler 9 that adds no new features but makes RAM Doubler compatible with Mac OS 9. If you’ve been missing RAM Doubler since upgrading to Mac OS 9, it’s well worth downloading. Unfortunately, Connectix has also stated that it has no plans to update the popular SpeedDoubler 8 or Surf Express Deluxe for Mac OS 9.