Thanks for your fast reply!
If your Intenret is lagging badly, all miners, not just mine, will have strange hashrate drops because its blocking on share submission.
This seems to be no problem for me. I stopped diablo and fired up phoenix, and after some time the hashrate shown at deepbit's web site shows ~270mhash/sec, like I expected. I'm not having any connection issues, only my router sometimes stops working.
Is there a console output I should be watching for in diablo to see if it is taking a long time to submit shares? Both hash meters (total and 15sec average) showed 270mhash/s. (And why not submit shares in a seperate thread so there is no blocking?)
In addition to that, less than -f 15 often causes the OS clock to get jerky up to the point that the 15 second average (the first number) becomes very unreliable. In these situations, use the forever average only (the second number)... it usually becomes reliable within a minute or two.
This seems to be no problem for me as well. I don't specify -f on the command line, so I guess it's using a default value. With diablo, there is pretty much no desktop lag for me (while phatk causes same lag). The gnome clock updates fine, so this should be fine.
Other miners suffer from this, but try various ways of covering it up; none are as accurate as using the forever average on mine over long periods.
As I said, the forever average looked okay.
It's still possible, due to the random nature of mining, that the relatively low number of submitted shares was bad luck. Or maybe there is a bug that only appears on some systems (i.e. my system) and possibly only with some configurations that causes diablo to
* calculate hashrate wrong OR
* sometimes not submit/recognize a share even if it is valid.
Wait, hold up. Theres your problem. Deepbit's hash meter is 100% inaccurate and is counting a rare random event, ie, share generation. Do not use Deepbit's hash meter as a measure of performance.
My miner tends to swing the randomness of share generation around harder (due to working on independent work in parallel), but otherwise has no effect on actual share generation.
Also, I may consider submitting shares in a separate thread in the future, however I already run 3 mining threads per GPU and this tends to eliminate usual network lag issues.