Once you get to this level of performance, the bulk of a SSD controller ASIC is essentially just high-performance switching fabric; directing the flow of data between the 8-12 channels of NAND flash, the PCIE bus, it's internal buffers and the DRAM.
If you have any experience with high performance networking equipment, you know that pure switching fabric ASICs generates a lot of heat on its own. Hell, even a dumb 5-port gigabit ethernet switch generates a surprising amount of heat, they are always warm to the touch.
I really doubt that handling the FTL layer on the controller adds that much extra power draw. A dumb PCIE <-> NAND switching ASIC will also have cooling problems.
I recently upgraded my home network to 10 gigabit and was surprised by the amount of heat generated by 10 gig switches. Why do pure switching fabric ASICs generate so much heat?
Gates consume electricity when they switch: some energy is needed to flip a FET from "open" to "closed" or back. Then the gate stays in a particular state for some time, allowing the circuit to operate.
The faster you switch a gate, the more often you have to pay the switching price, which cannot go too low, else the thermal noise would overcome it. So you spend roughly 10x the energy switching a 10 Gbps stream as you use for 1 Gbps stream. Newer, smaller gates consume less energy switching, but not 10x less.
If you have any experience with high performance networking equipment, you know that pure switching fabric ASICs generates a lot of heat on its own. Hell, even a dumb 5-port gigabit ethernet switch generates a surprising amount of heat, they are always warm to the touch.
I really doubt that handling the FTL layer on the controller adds that much extra power draw. A dumb PCIE <-> NAND switching ASIC will also have cooling problems.