I use Sapphire Trixx to downclock my memory to 150 Mhz which also increases hashrate due to tighter timings. 
how does downclocking the memory actually help? and, to me, this value seems insane!
are you sure you meant 150 Mhz ?I use Sapphire Trixx to downclock my memory to 150 Mhz which also increases hashrate due to tighter timings.
Using 15.7.1 and Trixx? Are You sure it's underclocked? Checked in Trixx card info or GPU-Z?
I'm absolutely certain, Trixx seems to be the only utility which allows you to do so without any hassle anyway. A wide variety of algorithms benefit from setting the memory to 150 Mhz [600 Mhz effective] such as Quark & Qubit which rely on latency rather than throughput. This sets your memory bus to a strap with tighter timings which will ultimately lower power consumption and heat and also allows for more overclocking headroom. To prove my point, I managed to yield 23 MH/s for Quark, a similar figure for Qubit and 37 MH/s Ethereum & 620 MH/s for Decred in dual mining mode on a 390x without rejected shares.
Has anyone tried Stilit's bios or any other modded bios for that matter on Ethereum?
15.12 Trixx and Win7 x64 I can only overclock, but not downclock. Trixx accepts downclock, pretends that it's done, but if I check in card info or GPU-Z clocks are default values.
MSI Afterburner reports that my memory is indeed running at 150 Mhz once set via Trixx. I have no other utilities present in this system which is why I cannot provide any other kind of confirmation. Try launching a game or anything else which can put a substantial load on your memory bus for that matter, such as Scrypt and you'll immediately notice a drastic decrease in performance. Out of curiosity, I "tried" to play a variety of games including Fallout 4, BF4 and GTA5 and let me say that what was once smooth sailing at 60 FPS is now a slideshow, which eliminated the last shred of doubt. 150 Mhz has proved to be optimal on my 290s, 290xs and 390xs as anything lower or higher seems to offset timings.
By curiosity I set memory for R9 290 to run at 150Mh, speed for ETH is aprox. 3Mh .... You are sure memory is indeed run at 150Mh, look at MSI Afterburner Hardware Monitor graph not in main window.
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