Fedora 2 + 1GB RAM = S-L-O-W

[cosmolee at speakeasy.net]

Fedora Core 2, Intel 915GEV mobo, 533 DDR2 ram, P4 w/ HT 3.0 GHz

I've found that some kernels of Fedora run EXTREMELY slowly when I have 1GB of RAM, including the recent 2.6.10-1.14.  

On my motherboard, I've tried running with one bank if 512MB of RAM and all is well.  But when I put in another bank of identical (same vendor) 512MB RAM for a total of 1GB, the system slows to a crawl.  Small tasks suck up CPU cycles, as if I'm running an i386.  As an indicator, I've measured bootup time to login screen.

My system boots to graphical login in about 80-90 seconds w/ 512MB, but with 1GB the system takes almost 8 minutes(!) to get to the login screen.  

Any ideas what is going on?  

Here's a list of kernels I've tried, both the single & multi-proc kernels behave the same:

2.6.10-1.14     Slow
2.6.10-1.9      Slow
2.6.9-1.6       normal
2.6.8-1.52      normal
2.6.8-1.02      Slow     (Win4Lin patched)
2.6.5-1.358     normal