I don't think that it is a cache conflict, I think that it is sharing the 66 Mhz memory bus that makes them slower. If I run just one instance, I get a unit every 12-13 hours. If I run 2, then each unit takes 18-19 hours so one is taking 9-9 1/2 hours.
I usually have Gnome running and I also fool around in C on my Linux box. All of this takes memory and slows things down some.
According to
http://pages.tca.net/roelof/setispy/default.htm#Tips, I should be taking about 9.2 hrs on the C433 (= 555(7.2/433)) and 10 hrs/unit on the C400 (555(7.2/400). The 12 hours seems a little higher than it should be, I am running the client all the time in the system tray. My daughter does use the computer for at least an hour every day.
My BP6 box is running way too hot (if lm_sensors can be trusted). I need to tear it down and take a look at the cooling. My CPU reading are in the low 60's C all the time unless I have the case open and a floor fan pointed at it. Some of the problem is the case design, the CPUs are across from the power supply so there's lots of hot air around the CPU.. I bought a new case fan, it should be arriving tommorrow. I also bought a slot fan to pump out heat from my Velocity 100 video card (it really doesn't run all that hot so that shouldn't make much of a difference).
I'm going to look at the fans and use thermal grease to get better contact. My room does get pretty hot at times (upstairs with 4-5 computers running all the time). I'm guessing the room is about 25 C and it must shoot up to 30 C - 32 C a lot. Since my airconditioning sensor is downstairs, it has to be fairly hot before the house AC kicks on.
I may have access to 6 - 10 P75's and P90's (work is dumping them). I may build a little Linux cluster with them just to see how that works. They'll only do a work unit every 50 hours or so, but 5 of them will do 2 work units a day. I'll have to clear room in my garage for them.
I'll have to bump the CAS setting to 2 for my memory on my SETI machines and see how that goes.
Michael