My guess is linux is showing you the capacity of the l2 cache (total on the die) of 4mb and the usable size (available cache) of 1mb.
What I mean by that, is the pentium dual cores are just core 2s with locked l2 cache (4mb for the core 2s the pentium dual core 4xxx series is derived from) so linux is just showing you the total physical amount of l2 cache, and the usable l2 cache as well.
What I mean by that, is the pentium dual cores are just core 2s with locked l2 cache
Thanks, guys, and especially pepperman. I didn't know the T4400s are locked Core 2s. For anyone else interested in this: a bit more googling suggested that unlocking L2 cache on binned CPUs used to be easier until around 2003 but is now a serious/impossible mod on Intel CPUs. Might be easier on some AMDs ("Advanced Clock Calibration" might be a good place to start your googling).