Im just trying to start using this. been usinbg cgminer guiminer-scrypt for months with various rigs, all over 500khash, tried multiminer with bfgminer and only get 15khash per card, pitifully lower than on cgminer.
Go into
Settings and then
Advanced backend settings and under Arguments enter the Scrypt arguments you provided to cgminer for your card, such as thread-concurrency. These settings are specific to each card and will require some research. For my 7950s I use:
-I 20 -g 1 --thread-concurrency 24000
GPU mining with MultiMiner should perform no different than using bfgminer alone or (in theory) cgminer.