The 225W Board Power rating does look smaller than the Vega64 and Radeon VII family ratings which range at 300W, but this is relatively high when compared to the expectations and speculation circulating on the Internet. With 7nm technology, enthusiasts seem to want a GPU with a 150W class rating down like when the RX 480 / RX 470 Polaris first appeared. With 225W, the RX 5700 XT appears to have a class of board power equivalent to the Radeon RX 590.
Graphite TEAM, Unique Shape of Cooling
The 225W GPU class definitely requires serious cooling, and AMD appears to use a 'Vapor chamber' cooler which is cooled by a single-fan blower. This design is similar to the cooler found on the reference version of the Polaris RX 480 / Vega 64 card, only AMD seems also trying to transfer heat more effectively by using Graphite TIM (This is used on Radeon VII).
What is unique, the physical form of the RX 5700 XT cooler looks 'dent'. AMD says that they are optimizing airflow and noise levels, and we can guess that the purpose of the 'curved' shroud form is intended to focus the flow of air to the vapor chamber which is positioned slightly downward, and this makes the single-fan blower will be slightly more effectively dissipates heat from the Radeon RX 5700 XT especially when the fan speed is low.
What about the Radeon RX 5700? The specifications are quite similar to the RX 5700 XT, the following specifications are the same: 7nm Fabrication Process, die size 251 mm2, 256-bit RAM 8GB GDDR6 14 Gbps, 64 ROP, 6-pin + 8-pin PCIe Power Connector, PCIe support 4.0 and Single-Fan Blower coolers.
Different? GPU Compute Unit specifications, Clockspeed, Power board rating, and cooling shroud form (we don't know whether the vapor chamber used is the same as the 5700 XT).
The Radeon RX 5700 is slightly cut, with 36 Compute Units (2304 Stream Processors) and 144 Texture Units.
Clockspeed is somewhat lowered to 1465 Mhz Base Clock, 1625Mhz 'Game Clock', and up to 1725 Mhz Boost Clock. This makes the GPU has a performance rating of 7.95 TFLOP / s single-precision compute.
The board power rating of the Radeon RX 5700 is 180 W, around 80% of the Radeon RX 5700 XT. It's easy enough to consider that this lower power board rating not only comes from the slightly smaller number of Compute Units, but comes from the clockspeed range. To achieve the RX 5700 clockspeed rating in the 1.6 Ghz typical Game Clock range, of course it requires a relatively lower voltage than the RX 5700 XT which uses high clockspeed - this makes the Radeon RX 5700 have a low power board rating.
We can be confident with this, that the performance per watt (Power Efficiency) of the RX 5700 will be better than the RX 5700 XT.