I have an HD 5750 with a stock clock of 700 Mhz afaik.
I've underclocked my memory, but that reduced my Mhash by 1% or so, so I had to get the core clock higher to compensate
I'm already at the point where I stop overclocking to play games on my computer because the current clock is too high for games to run without making my GPU reboot. But it seems that mining doesn't suffer from this, I can mine just fine when overclocking that much. It's only 700 -> 775 with memory being downclocked to 300.
So since the usual benchmarks already fail, how much more can I overclock my card before youtube starts crashing my gpu? Is it worth it to actually try this?
The only way to tell is to try it since every computer configuration and running environment is different.
Step it up 1Mhz by 1Mhz until you get a lock up. Then step back 1Mhz and see how long you can go before crashing. Then to be safe, I'd back off another 5Mhz from that at least.