OK, tried a few more things and got mixed but not results that I can make use of but thought I'd share in case it helps anyone else or someone has some ideas.
I set
with 2 I only got 3 GPUs #ing.
Now with 4 GPUs running I started to fiddle with the clocks.
With all memory clocks on 1725 and all gpu on 1030 I get 4 cards running.
With all memory clocks on 1750 and all gpu on 1045 I get 3 cards running.
Now I try to set the mem clocks individually (all gpu clocks back to 1030):
1750,1725,1725,1725 = 4 cards OK
1750,1750,1725,1725 = 3 cards OK
1750,1725,1750,1725 = 2 cards OK = now this is strange as I'd expected it to be 3 cards at worst.
1750,1725,1725,1750 = 4 cards OK.
At this point # rate is dire: 416, 276, 157, 283. Useless.
I then start to fiddle with the GPU clocks but this just leads to cards doing nothing again (even though the clock is in range for the card).
1045,1030,1030,1045 = 3 cards
1045,1030,1030,1030 and removed --shaders but still only 3 cards
Leaving --shaders out I try all cards on 1725 again (all back to 1030 gpu) and I only get 2 cards going so I put shaders back in.
I go back to 1750,1725,1725,1725 (with shaders back in) and I get a # of 417,259,373,311 which is a slight improvement but still useless.
I now try tweaking the GPU based on the lower limit with the 0.57 - 0.6 ratio and set the gpu clocks 1030,1015,1015,1015
which gives 417,276,408,281 #.
I'm using Ubuntu 12.04 LTS with CGminer 3.2.2 and one thing that makes this process slower than is should be is that when I hit Q to stop CGminer it does stop but the process does not end. I can kill it but if I then try to use CGMiner again it doesn't work so every time I try some new parameter I'm having to reboot. Perhaps this is a clue?
Arrrgh! It's a hot day & even hotter than the devils ring after a napalm curry where I have the machine (even with aircon) so I set the machine back to SHA-256 & give it a rest while I read up for more ideas... but with all the ASICs coming on-line I need to turn this machine around for scrypt.
