I have in my PC 1x5870, 1x5970 and 2x6990. Use clocktweak 0.9.2b and when try set memory clock to 450MHz using –memlevel0 and –memlevel1 and memlevel2. All cards show in afterburner 450MHz when cgminer is off. When I start cgminer memory clock for 5870 and 5970 are 450MHz bur for 6990 rise to 1250MHz. After close cgminer all memory clock for all cards show 450MHz. But when I use afterburner and set unofficial overclocking mode 2, and set 450MHz mem clock for 6990 all is OK. When I start and close cgminer all cards have 450MHz after set by afterburner. How can I set mem clock for 6990 by clocktweak, and keep this when GPU starts work? Need any help.