PC's is a possessive form, PCs a plural one: The plural of peecee is peecees, not peecee's.
Index: i386.html =================================================================== RCS file: /cvs/www/i386.html,v retrieving revision 1.735 diff -r1.735 i386.html 19c19 < OpenBSD/i386 runs on the standard PC's and clones, with a wide variety ---
OpenBSD/i386 runs on the standard PCs and clones, with a wide variety
48c48 < Machines using custom BIOS (such as older proprietary PC's, laptops, and some ---
Machines using custom BIOS (such as older proprietary PCs, laptops, and some
