MicroSD Speed? (UHS?)
#1
Does the Rock64 support UHS speeds for the MicroSD card? 

Usually the answer is no (requires switching to a lower voltage AFAIK). USB 3.0 is a welcome addition, but given how cheap high speed MicroSD cards are, it would be nice to finally have an SBC that can take advantage of them. To have to use a USB 3.0 MicroSD adapter though... that would be uncool.

And yes, I understand eMMC is faster. That just tells me the BUS can handle it.

Thanks.
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#2
Good question.
But given that there is reasonably priced eMMC available for the Rock64 (which has much better performance than just about any SD) I cant see it being super relevant. That said, I will try to find out Smile
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#3
Relevancy: When you need more than 64 GB of capacity and don't want to bottleneck the eMMC (or have a hard drive dangling out). MicroSD cards come in 256 GB today, and 512's soon.
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#4
From what I can interpret out of the RK3328 datasheet, it probably supports UHS-I (up to 104MB/s bus rate), but not any higher class.

As Luke already said however the eMMC is faster. That interface can handle up to 200MB/s transfer.
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#5
I read the RK3328 datasheet MicroSD iCompatible with SD 3.0  this mean maybe faster than pinea64 the pinea64 is used SD 2.0?
If I am wrong please correct my content , thank !



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#6
(07-04-2017, 05:59 PM)PoV Wrote: Relevancy: When you need more than 64 GB of capacity and don't want to bottleneck the eMMC (or have a hard drive dangling out). MicroSD cards come in 256 GB today, and 512's soon.

And not to mention more SSD-like IOPS  (A1 Rated cards are capable of 1500 read I/O operations per second and 500 write ones.  A2 rated cards look/act more like NVMe cards...)- and some of the hottest SD cards in 64/128/256 weigh in at UHS-I speed grade 3 and A1 applications performance grade.  This means it's just like taking a USB HD and plugging it in.

Can the controller interface cope with and leverage these new SD cards?
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#7
(07-05-2017, 08:02 AM)joe Wrote: I read the RK3328 datasheet MicroSD iCompatible with SD 3.0  this mean maybe faster than pinea64 the pinea64 is used SD 2.0

"Compatible" is slightly differing than "uses".  UHS-I is effectively the SD 3.0 specification for all intents and purposes.  All 3.0 devices are "compatible" with the 2.0 interface, they just are able to run faster on a 3.0 bus.

As an aside to all- when you're talking <X>MBps on a given specification, that is the signalling rate of the interface.  There are NO assurances that any given device, including the eMMC cards, will leverage all of that speed.  You must take into account number of lanes (bits) for the data, how many I/O operations per second the device will provide, etc.  If the eMMC does only 500 IOPS for the read, for example, an A1 SD card will VAPORIZE it on read (1500 IOPS minimum on read to make an A1 cert...) if you're operating in 4 bit mode against 4 or 8-bit mode on the eMMC.  This is because it can address 3 times the requests, saturating the SD/MMC bus where the eMMC in this example can't even get there.

Empirical (measured) analysis of both interfaces is in order, to be honest.
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#8
The SD card interface is fixed at 3.3V I/O. To support high speed modes (using clocks beyond 50Mhz) you need 1.8V I/O voltage like on the eMMC interface. You could switch the SD card interface to 1.8V on a design but that removes backwards compatibility with slower/older cards that can only do 3.3V I/O. You could implement a dual level I/O scheme supporting both 1.8V and 3.3V but I haven't seen anyone going through with that on a cheap SBC design. If you want high(er) speed storage on Rock64 you need to go with the USB3 port.
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#9
Depending on manufacturer and card, you can cheat a bit and eke out 40-ish MBytes/sec out of the interface (You can do it on the Pi3's where they have a similar story on the MMC controller. As for cheap designs...that's a depends thing. It might run the price up another 10-ish to do the dual voltage design- because they do it pretty easily with the USB MSD card readers and Cypress does it out of box with their FX3's if you use their ref implementations.

Well, then...that kind of settles it. With a UHS-1 capable card, of the right type, you can cheat and push the thing a bit at the 3.3v levels (Doing it now on a couple of PI-3's) and see the card crank out 40-ish MB/s on the interface. It's still semi-viable with stock or slight overclock- you will need a U-1 or U-3 card, preferably rated A1 or better for it to matter. eMMC's...anyone know what they benchmark out at?
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#10
I posted iozone results for the eMMC I have in my Pinebook a while back, Rock64 uses the same eMMC modules, but I havent run iozone on one yet....

https://forum.pine64.org/showthread.php?...8#pid28248
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