# Regarding SD card max speed on FU-540 board

**URL:** https://forums.sifive.com/t/regarding-sd-card-max-speed-on-fu-540-board/4963
**Category:** HiFive Unleashed
**Created:** [July 12, 2021, 6:02am UTC](https://forums.sifive.com/t/regarding-sd-card-max-speed-on-fu-540-board/4963 "2021-07-12T06:02:17Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![Bharath29](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@Bharath29](https://forums.sifive.com/u/Bharath29)
#### Post date: [July 12, 2021, 6:02am UTC](https://forums.sifive.com/t/regarding-sd-card-max-speed-on-fu-540-board/4963/1 "2021-07-12T06:02:17Z")

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Hi all,  
Can anyone tell me, what is the maximum speed which support by MMC IP on Hifive Unleashed (U540) board?

```
Now as default it is working with 20Mhz. Is there possible to change the speed (25Mhz, 50Mhz and 104Mhz) configuration in dts file?

```

Thanks & Regards,  
Bharath T

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### Author: ![jimw](https://avatars.discourse-cdn.com/v4/letter/j/f14d63/32.png) [@jimw](https://forums.sifive.com/u/jimw)
#### Post date: [July 12, 2021, 6:48pm UTC](https://forums.sifive.com/t/regarding-sd-card-max-speed-on-fu-540-board/4963/2 "2021-07-12T18:48:02Z")

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I doubt that the SDcard can run faster than it already does. The solution to the SDcard problem is to avoid using it. An NFS filesystem will be faster than an SDcard filesystem. Fedora has support for an NBD root file system which is also faster than an SDcard root, though an NBD root can be tricky to set up.

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### Author: ![bruce](https://sea2.discourse-cdn.com/flex020/user_avatar/forums.sifive.com/bruce/32/452_2.png) [@bruce](https://forums.sifive.com/u/bruce)
#### Post date: [July 13, 2021, 1:26am UTC](https://forums.sifive.com/t/regarding-sd-card-max-speed-on-fu-540-board/4963/3 "2021-07-13T01:26:02Z")

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SD cards are never fast at the best of times. This is compounded on the FU-540 by the chip only supporting SPI mode not SD mode.

It’s probably possible to change the SPI clock, but it’s never going to be fast.

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### Author: ![Bharath29](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@Bharath29](https://forums.sifive.com/u/Bharath29)
#### Post date: [July 22, 2021, 6:10am UTC](https://forums.sifive.com/t/regarding-sd-card-max-speed-on-fu-540-board/4963/4 "2021-07-22T06:10:04Z")

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Hi guys,

Thanks for your responses and i got the information.

Thanks & regards,  
Bharath T