Actually, the Rayovac 840 is rated at 4.5v 800 mAh, so putting in
3*AAA is a reasonable (and "cost effective") thing to do. But the
footprint is a tad larger. There's room...
The NetBSD pages specifically mention a FCT623 as the cause of
problems but I didn't want to get into that mess unless I had to... A
Linux FAQ claimed that changing the video or serial cables could also
cause problems.