The Guru of 3D published a review on the Radeon R7 370 - R9 380 and R9 390X
A quote from the article:
We review the MSI Radeon R9 390X Gaming 8G OC. The card's equipped with that Hawaii GPU, now called Grenada. Thanks to a huge triple slot cooler based on the TwinFrozr V design the product is spinning & purring at just roughly 75 Degrees C, that's under full gaming load. The 2816 Stream processor based Hawaii/Grenada chip will get paired with 8 GB GDDR5 memory running along a 512-bit memory interface. The card itself is fully customized including component selection, custom PCB, custom cooling, well... custom everything! Powered through 8-Pin + 6-Pin power configuration it obviously runs at factory overclocked specifications as well. The card will clock towards 1100 MHz (from 1050 Mhz) with a memory clock at 6100 MHz coming from 6 GHz for the reference product.Radeon R7 370 - R9 380 and R9 390X Review @ Guru3D
So to clear up some confusion from the get-go, this product is based on the Hawaii GPU released back in October 2013, the silicon is the same yet with a few tweaks applied the product is now called Grenada, the latest iteration of the asic. It is the very same 6 Billion transistor GPU on that 28nm fab based 438 mm2 Die. Over time the fabrication will however yield better; much like fine wine the latest iterations of the silicon evolve, hence they can now be clocked a notch faster. The memory is tied to a 512-bit memory bus with one distinct difference, you now get 8 GB of graphics memory. That memory is tweaked and clocked a notch faster as well, 6 GHz (effective data-rate) for the reference products, with the MSI model tested today running 6.1 Gbps (GDDR5) memory. The 390X GPU will get a reference clock of 1050 MHz, this MSI SKU is factory clocked at 1100 MHz. So, overall coming from the 290X you should see performance increases running up-to maybe 10% overall, depending on the card you purchase. With the recent focus on Ultra HD gaming, AMD is also marketing that to be pretty significant, hence that 8 GB of graphics memory. It's not new though as there have already been 8 GB SKUs of the 290X available for over a year, let's do mention that as well.
The tweaks on the GPU and memory clocks however seem to be the biggest change, the rest is complimentary from the board partners. As stated, the MSI Radeon R9 390X Gaming 8G OC edition card is tweaked a little better for you, its GPU may run upwards to 1100 MHz with 6100 MHz (effective) on the GDDR5 memory. The all custom PCB with Grenada is being cooled with the new model TwinFrozr V cooler. Since 390X is clocked higher, the GPU needs more voltage, that also means a need for better cooling. The TwinFrozr model cooler is now just over 2 slots wide, but let's call this a three slot cooler. The product remains fairly quiet, in idle / desktop mode the fans won't even spin. You get color lighting options to change the logo to a color of your preference.