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Comment by swarnie | Hacker News Reader

What's the issue with a jump from 12w to 25w?

We're talking about an SSD form factor that's 22x80mm and is fed by a couple of card edge pins carrying 3.3V. 12W was already pushing it.

According to the one-page datasheet of a Foxconn M.2 M-key socket, maximum current per pin is 0.5 A (they're tiny, after all). Since M.2 M-key has a total of nine pins carrying 3.3 V this would limit power to 15 W before any heat dissipation considerations plus connector derating because the toasty SSD is heating the connector up.

...on a device that weighs about 10 grams with a heat capacity likely around 0.4J/gram-degrees-C.

10Ws for such a device if I did the math right is around a 2.5C/sec rise in device temperature.

The M.2 sockets on motherboards don't exactly have great cooling, and SSDs don't usually even come with radiator.

The positioning can also be pretty iffy, mine have one next to CPU, another just under GPU (no chance getting fan there) and those are the "fast" (directly connected to CPU) ones!

The another 2 slots are again under GPU (one filled with wifi/bt card), and only last 2 are far away from other hot components and get its own heatsink. but those are not directly connected to CPU

I don't think this would be a factor. Some PCI-E 4.0 SSDs already come with metal heatsinks out of the box. If future SSDs needs addtitional cooling, this will be communicated to the buyer.

I think that the bigger question is whether 25W can be phisically supplied to the drives by contemporary motherboards. What is the power limit for the m.2 ports?

At least according to wikipedia each pin is rated up to 0.5A with I think nine 3.3v pins so technically just around ~15W peak

Technically that's what U.2 (2.5 inch form factor for SSDs) would be for.

They get 5V/12V and thicker connector, I severely doubt M.2 could swing 25W as it only has 3.3V on it

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