Yeah, I now realize I should have said every few minutes, a "twitch" occurs, rather than every few seconds (which is true under heavy load).
And I have Voodoo 9.5.0. Could the lack of RAM combined with PATA drive be to blame?

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Custom Hackintosh...AMD Athlon X2 5000+ (2.6 GHz) on GA-MA78GM-S2H...Linksys WMP300n Wireless...ALC889a sound...ATI HD 3650 PCIe...1 GB DDR2 RAM...320GB Western Digital SATA + 200GB Seagate IDE HDD...Rosewill DVD-RW IDE...Running Kalyway upgraded to 10.5.7...All Fully Functional