Well shoot, it seems that 880 is the max for mine. Odd thing is that it gives errors without throttling, but cgminer doesn't report them. So cgminer makes things look like all is well, but in fact the device is returning bad results, and HW: remains at zero but share submission rate tanks.
The HW: number is simple - any share returned by any device is checked (it is sha256'd)
If it is invalid, it is a HW: error, if it is valid, it continues down the chain of processing.
Thus a HW: error means the device's sha256 isn't functioning correctly somehow
In GPU terms, it usually means it's OC too hard.
As I mentioned above, with a ztex it means the MHz clock is up too high and needs to be stepped down a bit (that's what the cgminer code does)
But in both cases, the meaning is the same.
On the other hand, if USB device I/O returns an error, then of course that isn't considered a HW: error, since that is a USB issue.
Yes I've seen someone with 6 BFL's have them return USB errors regularly due to some problem with the USB configuration and the OS
But that is exactly that, a USB problem, not a HW: error (since HW: has that specific meaning and in this case the fix is not related to the device failing to sha256 correctly)
