No UHS-II port on any Surface so far; UHS-I support unclear

[RajeevT]

I was wondering whether the SP3 supports SDXC v4.0 specs i.e. the faster UHS-II MicroSD cards instead of only v3.01 i.e. UHS-I or slower cards, and wanted to share the results of my research.

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As you can see above UHS-II cards have a second row of pins, so they're backwards-compatible with UHS-I or SDHC/SDXC devices but will only run at UHS-I or lower speeds in such devices, since obviously the older ports won't be able to access the additional pins.

Microsoft is extremely evasive about this for some reason, only saying "Surface currently supports all MicroSD cards available in the market today", which is no answer at all. Thankfully the folks over at iFixit have torn down all the devices and we know that the Surface Pro and Pro 3 MicroSD ports (same goes for all the rest including the RT/2) cannot access the second row of pins necessary for UHS-II support:

Surface Pro MicroSD port
View attachment DTjaq5s.jpg
Surface Pro 3 MicroSD port (one on the right)
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Ok, so UHS-II is out of the picture. But what about UHS-I? Again no help from Microsoft and since UHS-I SDHC/SDXC cards are physically (externally at least) no different from non UHS-I cards, no way to tell really. Measured speeds seem to suggest UHS-I is supported, but shame on Microsoft for not providing a clear-cut answer or detailed technical specs on the hardware inside their devices.

A few quick points:

• SD cards - up to 4GB, SDHC - up to 32GB, SDXC - up to 2TB
• All ports are backwards-compatible, so SD cards can be used in SD, SDHC and SDXC ports
• Similarly SDHC cards can be used in SDHC and SDXC ports
• SDXC cards can be used only in SDXC ports
• SDHC and SDXC cards can additionally support the UHS-I and UHS-II bus for higher speeds
• SDHC and SDXC UHS-I/II cards can be used in non-UHS SDHC and SDXC ports
• Class ratings indicate minimum write speeds supported and thus far include Classes 2, 4, 6, 10, U1 (UHS Class 1) and U3 (UHS Class 3)

Finally, if anyone can locate detailed technical specs about the MicroSD port in the Surface devices to confirm UHS-I support that would be great.

 

[wertzius]

UHS-1 SDXC is available at the Surface Pro. It can read at max Speed (90 MB/s) from 600x Micro SDs with 64GB.

 

[RajeevT]

UHS-1 SDXC is available at the Surface Pro. It can read at max Speed (90 MB/s) from 600x Micro SDs with 64GB.

Yes, that's what I meant when I said "measured speeds seem to suggest UHS-I is supported". Also note that in the numerous threads I've seen about this on the net many people have reported they failed to observe those high speeds with new UHS-I cards on their Surface Pros. Still that's the closest we'll get I suppose to absolute proof unless some actual documentation is uncovered.

If someone is an SD card expert perhaps they could tell us if software exists to reliably detect whether UHS-I hardware support exists or not? I don't see why this wouldn't be technically possible, although no such program might have been written yet or it might only be available for internal use by a card manufacturer's employees.

BTW, what does "600x" mean anyway? The x ratings are obsolete and there's no standard on whether it refers to read or write speeds. Lexar (the only one that seems to sell "600x" cards) claims "600x = Up to 90MB/s guaranteed minimum sustained write speed", which is funny because if it's a "guaranteed minimum" how can it be "up to"? Also I don't quite believe them because 90MB/s write speeds would be well in excess of any of the class ratings I mentioned above (it's equivalent to thrice U3's speeds).

 

[Ruined]

Personally I wish they put a fast, full sized SD port in surface.

 

[RajeevT]

Personally I wish they put a fast, full sized SD port in surface.

The hardware will probably cost more and draw more power too. SD cards may be slightly cheaper but similarly speed class rated MicroSD ones should have equivalent performance so what will be the advantage? For photographers who swap SD cards frequently between their cameras and their tablets it would help, but many popular (video) cameras nowadays such as GoPro Hero3/3+ series take MicroSD cards. MicroSD cards can of course also be used with an adapter in devices that take SD cards.

 

[wertzius]

The max speed rating of 90 MB/s is always only the reading speed.

600x means 600 times the speed of a 1x CD drive (150Kb/s).
600x = 90 MB/s.

There are also some 633x Micro SDs available. The 600x/633x Label is the only way to recognize the fastest available cards.

The fastest Micro SDs are only in capacities up to 64GB available, SD Cards with up to 128GB. That is the main advantage of SD Cards.

There is no doubt that the Surface Pro 3 supports UHS-1. No proof needed.

 

[RajeevT]

The max speed rating of 90 MB/s is always only the reading speed.

Lexar seems to believe it refers to the write speed. They should correct their website if the info's wrong. Also, as I mentioned above the class ratings indicate minimum write speeds supported to record video. So it doesn't matter what read speed is claimed since that's apparently not a factor at all in the ratings. Further, the minimum write speed performance for both Class 10 and U1 is 10MB/s, so if you see the Surface writing at that speed or higher you cannot automatically conclude it supports UHS-I, because it could simply indicate Class 10 support.

The fastest Micro SDs are only in capacities up to 64GB available, SD Cards with up to 128GB. That is the main advantage of SD Cards.

True, since miniaturisation takes time and increases costs the higher speeds are available with SD cards first and with MicroSD ones later. Anyway, the decision to offer an SD or MicroSD slot rests solely with Microsoft. I'm comfortable with either option.

There is no doubt that the Surface Pro 3 supports UHS-1. No proof needed.

Given the issues mentioned above I'd say proof is still needed and would like to see some official confirmation. Why does Microsoft not clarify this point and clearly mention UHS-I on the port or at least the online/paper documentation? What's stopping them from doing so?