How to increase SD card read speed on rooted HTC EVO 4G

Evo-sd-read-fix

Noticed something strange when you tested the transfer speeds of your HTC EVO’s microSD card? The write speed was probably fine, but I bet your read speed was capped at 5 MB/s, a far cry from the capabilities of your Class 6 or Class 10 card.

The problem isn’t your card; it’s the EVO. Just as the handset used to have that 30 fps cap on graphics performance and currently has a cap of sorts on 3G speeds, it’s also got a limit enforced upon its SD card read speeds.

Fortunately, there’s an easy way to break through the barrier and significantly increase those read speeds if your EVO is rooted (yet another benefit of rooting) and you’ve got a root file manager.

My favorite file manager and one of G&E must-have root apps is Root Explorer, so that’s what the following tutorial is based on. Other root file manager will work just fine too, but the exact steps may be a little different.

1. Download Root Explorer (£2.50) from Android Market or scan the QR code below.

Evo-rootexp
Evo-sd-bdi 2. Open the app, scroll to the bottom, and tap the sys folder.

3. Then tap devices > virtual > bdi > 179:0.

4. Long press read_ahead_kb and select Open in Text Editor from the options menu that appears (it should be the second to the last item listed).

5. You should see a lot of white space and a single number in the first line. If the value is 4, replace it with 128. If the value is already 128 (some devs bake it into their custom ROMs), then you don’t need this fix.

6. Press the Menu button on your EVO and tap Save & Exit (or just Exit if you didn’t have to make any changes in the previous step).

7. Test your card’s transfer speeds and thank sibere, frankoid, and lahma69 from the xda-developers forum for discovering/sharing the fix.

IMPORTANT: Rebooting your EVO will reset the read_ahead_kb value back to 4. If you don’t want to re-do this fix after every reboot and you’re not running a rooted stock ROM, Beknatok and akazabam have a flashable .zip solution for you here.

Thanks, Raymond & Joshua!

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Jenn K. Lee

Jenn K. Lee is the founder of Pocketables. She loves gadgets the way most women love shoes and purses. The pieces in her tech wardrobe that go with everything are currently the Samsung Galaxy Note II, Sony Tablet P, and Nexus 7, but there are still a couple of vintage UMPCs/MIDs in the back of her closet.

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