# The reading speed of SD card is too slow, only 1.4mb/s. How to improve the reading speed of SD card

**URL:** <https://forums.developer.nvidia.com/t/the-reading-speed-of-sd-card-is-too-slow-only-1-4mb-s-how-to-improve-the-reading-speed-of-sd-card/186787>\
**Category:** Jetson Nano\
**Tags:** board-design\
**Created:** [August 17, 2021, 11:31am UTC](https://forums.developer.nvidia.com/t/the-reading-speed-of-sd-card-is-too-slow-only-1-4mb-s-how-to-improve-the-reading-speed-of-sd-card/186787 "2021-08-17T11:31:24Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![WayneWWW](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/waynewww/32/14043_2.png) [@WayneWWW](https://forums.developer.nvidia.com/u/WayneWWW)\
**Post date:** [August 18, 2021, 2:21am UTC](https://forums.developer.nvidia.com/t/the-reading-speed-of-sd-card-is-too-slow-only-1-4mb-s-how-to-improve-the-reading-speed-of-sd-card/186787/3 "2021-08-18T02:21:58Z")

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What is the release version you are using? I remember max-clk-limit has already been removed from Nano dts for quite long.

The device tree is also wrong. Lacking of cd-gpio and vmmc-supply. That makes you not able to remove the max-clk-limit.

For old release \<=32.2. Below thread includes the need.

> [@Jetson nano SD card can use,but kernel prompt error](https://forums.developer.nvidia.com/t/jetson-nano-sd-card-can-use-but-kernel-prompt-error/154587/3):
>
> Hello, The basic device tree change for enabling sdmmc3 [https://forums.developer.nvidia.com/t/microsd-card-not-detected-on-jetson-nano-production-module/80776/14](https://forums.developer.nvidia.com/t/microsd-card-not-detected-on-jetson-nano-production-module/80776/14) If you notice the mmc speed is slow, please try this patch. [https://forums.developer.nvidia.com/t/slow-sd-card-access-speed-read-write-with-jetson-nano-production-module/111749/31](https://forums.developer.nvidia.com/t/slow-sd-card-access-speed-read-write-with-jetson-nano-production-module/111749/31) Some other forum users notice if tring warm boot, the speed becomes slow again. Turns out this patch is also needed in kernel [https://forums.devel…](https://forums.developer.nvidia.com/t/jetson-nano-sd-card-enters-back-to-high-speed-mode-instead-of-uhs-mode-after-soft-reboot/119041/4)

And this thread is for rel-32.5.1 that was just done last week.

> [@Micro-SD card on custom jetson nano](https://forums.developer.nvidia.com/t/micro-sd-card-on-custom-jetson-nano/184294/74):
>
> Ok, the last dtb: sdhci@700b0400 { compatible = "nvidia,tegra210-sdhci"; reg = \<0x0 0x700b0400 0x0 0x200\>; interrupts = \<0x0 0x13 0x4\>; aux-device-name = "sdhci-tegra.2"; iommus = \<0x30 0x1b\>; nvidia,runtime-pm-type = \<0x0\>; clocks = \<0x26 0x45 0x26 0xf3 0x26 0x136 0x26 0xc1\>; clock-names = "sdmmc", "pll\_p", "pll\_c4\_out2", "sdmmc\_legacy\_tm"; resets = \<0x26 0x45\>; reset-names = "sdhci"; status = "okay"; tap-delay = \<0x3\>; trim-delay = \<0x3\>; mmc-ocr-mask = \<0x3\>; ma…

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