SDXC Slots with UHS support ?


Inqui

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Hi guys,

I can´t find somthing in this board or at the blog about the SD-Slots of the Pyra.

Only "2x SDXC" slots are mentioned at the blog.

I´m not in the material, but do´s SDXC supports definetly UHS-1 or 3 ?

Because I was thinking about the speed win with an PC when an harddrive changed to an SSD.

When the Pyra is working only with Class10 SDXC Cards, that only would mean definetly 10Mb/s read/write. or ?

Wouldn´t that be an bottleneck ?

Only my thoughts ´bout rising the systemspeed (standby and that)

Thanks
 
The class specified on an SD card is the *minimum* consistent write speed, assuming reading is faster (which is almost always is). IIRC the Pandora's SD cards top out at only slightly above that value, so there's room for improvement there.


But I have to ask what you need that speed for. Don't forget that 1x CD speed is 150KBps, and DVD 1x speed is barely three times that, so even a class 1 SD card is equal to over 6x CD (class 1 SD does 1MBps, not 1Mbps, note). The Pandora is already faster than the fastest optical drives out there.


Granted, we don't boot off DVD for good reason, and the Pandora is definitely slower than hard disc, but given its OS is...


Damn, post truncated by the boards. Don't have the time to write it all out again right now, but I'll just note I was talking about boot times, playing video and swap files.
 
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The OS doesn't go on the SD cards by default, so SD speed isnt the bottleneck for OS operations.
 
The OMAP5 has one UHS MMC port which is being used for the internal storage. You can get a UHS microSD card and use that, potentially getting up to 96MB/s transfer speeds, but it would have to remain inside.

The external SD slots operate at standard high speed, same as the Pandora, with a maximum theoretical speed of 24MB/s. There is some overhead which reduces the speed on the Pandora to about 16MB/s at best, the Pyra will probably be similar.

edit: also if your use case does require large and fast storage, you may be pleased to know that it is planned to have an eSATA port on the back which should be capable of operating at up to 3Gbps (375MB/s)
 
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The OMAP5 has one UHS MMC port which is being used for the internal storage. You can get a UHS microSD card and use that, potentially getting up to 96MB/s transfer speeds, but it would have to remain inside.


The external SD slots operate at standard high speed, same as the Pandora, with a maximum theoretical speed of 24MB/s. There is some overhead which reduces the speed on the Pandora to about 16MB/s at best, the Pyra will probably be similar.
Didn't know that.

That really sucks.

I thought they were all UHS-I
 
Thanks for these informations.


So I was though about booting from a SD.


Like Ubuntu 12.04 arm is not that small os, and booting from an standard SD is not the holy gral


Also looking into the future, when the Pyra is working for that time like the pandora is doing.
 
Yeah, booting from SD isn't a necessity, and if I can boot from internal micro SD even faster than that's all to the good. While I've not needed to make use of the fact I can corrupt my Pandora OS and easily get it back, I like that it's there.


FWIW, last I heard, we couldn't put a microSD and a SIM card into the slot at the same time - is that still correct?
 
FWIW, last I heard, we couldn't put a microSD and a SIM card into the slot at the same time - is that still correct?
From what I understand it's a dual socket allowing a SIM card and uSD card at the same time. What can't be used at the same time is the internal eMMC memory and the uSD as they share the same bus.
 
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The OMAP5 has one UHS MMC port which is being used for the internal storage. You can get a UHS microSD card and use that, potentially getting up to 96MB/s transfer speeds, but it would have to remain inside.


The external SD slots operate at standard high speed, same as the Pandora, with a maximum theoretical speed of 24MB/s. There is some overhead which reduces the speed on the Pandora to about 16MB/s at best, the Pyra will probably be similar.
Didn't know that.

That really sucks.

I thought they were all UHS-I
Are you sure, WizardStan? I was always assuming that all SD slots would have SDR104 speeds (UHS-I). It would really suck if there is no speed improvement at all for the external slots.
 
They might, the data manual doesn't explicitly say that they don't, but it does explicitly list several modes for each port, of which the eMMC/MMC1 interface have several standard and high speed modes, while the MMC3 and MMC4 ports have just standard and high speed (48Mhz) listed. MMC5 apparently supported SDR50 but was removed from the OMAP5432.

Wait wait, wait. My bad!

I knew there was a mistake somewhere. MMC1 is just an SD interface, that supports SDR104. I thought the document was listing the eMMC and SD interfaces separately but this was wrong; the eMMC is actually MMC2 and lists all features of SD and eMMC modes in the same section.

So to recap, the internal storage will be an internal eMMC and a microSD interface which will both physically connect to the same port, MMC2, meaning you can only use one or the other BUT they operating at SDR104 speeds allowing you to (not accounting for overhead) get up to 192MB/s on an eMMC and 96MB/s with a UHS microSD card.

There is also a pure SD interface, MMC1, that supports the same UHS speeds. ED will probably make this the left SD slot.

There are then 2 more SD interfaces that operate at standard speeds, one specifically designated WSDIO for wifi, the other will probably be the right SD slot.
 
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