Ok, so were 3 days 5 hrs in on the 243.75's and I've noticed some drops in hash. I know machines have variance of +/- 10% sometimes but it seems like a steady but slow decline. What's weird is the time passed being only 2 days and change, compared to say a month or something.
Anyone else get this with OC'd machines ?
Power supplies. They're probably close enough to the edge of the kind of power the S3's like (beefier than they draw) that just staying hot for a long time is enough to suck hashing power.
Do you have 2 PSU's on each OC'd unit, or only one? And are you using two separate 6-pin PCI power connectors for each blade (not daisy-chain style) or only one?
My suggestion is to either cool the PSUs and see if your rate goes up, or use more/better PSUs. Poor power doesn't always show up in x's or -'s now that I've been playing a bit with my good S3 and just got 60 GH/s back by adding another PSU.
Worth a try!