May be try with this one samsung 3.2. its not that tight.
TRCDW=14 TRCDWA=14 TRCDR=25 TRCDRA=25, CL 21
777000000000000022CC1C00CEE55C46C0590E1532CD66090060070014051420FA8900A00300000 012123442C3353C19
or
copy your original bios 1500 strap to 2000. This would work too.
p.s. I see no real need to undervolt the mem to 900 since your core volt is not that low. you can keep the mem at 1000.
Want to use less power

Thanks. Tried that yesterday. Only got 28.x hash.
Micron gives me 30.9