Well first, your BIOS is out of date. Try updating that first.
While CPU-Z reports your BIOS as version 1002 of Motherboard P4S8X-X, the specifications for your HP box says it's something else - a P5LP-LE.
In either case, your BIOS version is out of date.
Lastly, the answer to your question lies in the "staging" of the L2 Cache. - Or you could say that the access granularity results in the "increased latency". Technically, the test is detecting the cache correctly, and incorrectly depending on how you look at it. Obviously in your CPU there is more than one stage of the level 2 cache, or there is an access granularity issue, where only a certain amount of L2 cache can be pulled from one access method.