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

  • I did this trick a few days ago and it has worked like a champ. It’s important to test different sizes and see what works best for you. Lower numbers are better for small files and random reads (most normal usage). Bigger numbers are better for large sequential reads like music and video. 64, 128 or 256 is probably a good setting for most, I’ve found 256 to work best for me.

    Reply
  • I just tested mine and I haven’t done the changes and my speed was already at 9mb. I guess mine is not capped since I have a custom rom. Either way its good to have this option but unless the test was wrong my phone is reading at over 5mb already.

    Reply
  • I put mine at 128 (from 4), before it was 1mb read, 2mb write, now it’s at 1mb read, 1mb write.

    Oh well. It’s an 8GB card with about 600MB free, so maybe that’s the problem; you have to have several gigs of free space for real speed. I didn’t think it would actually slow down though, but still, I like the sd speed app—very interesting.

    I visit this site every day, love it.

    Reply
  • Correction.

    When I put in the 128 value and save and exit, it apparently does nothing—–when I go back to view the same file, it once again reads “4.”

    Any idea why that wouldn’t work? Sure sounds easy, and was easy enough to do, but it didn’t change anything?

    Reply
  • Question I’m new to all this so how do you know if ur phone is rooted or not

    Reply
  • running stock and mine is already 128.

    Reply
  • Avatar of Jeremy

    If you haven’t rooted your phone, it’s not rooted. The don’t come stock-rooted.

    Reply
  • Avatar of Jeremy

    Class 4 16GB card. Now at 5MB Write and 14MB Read. I have a lot of pics and they pull up very fast now in the Gallery.

    Reply
  • Holy crap. That sped things up immensely…looking at my gallery is not painful anymore!

    Question….why do they cripple things like this and make it frustrating? I can’t see any technical reason why setting that low would be a good idea.

    Reply
  • What file explorer are you using? Astro won’t edit system files. You’ll need root explorer.

    Reply
  • What’s with HTC arbitrarily capping everything on this phone? They seem to be clueless.

    Reply
  • Ok, I have an 8GB Class 6 card. My results are as follows:

    4 – Write: 4MB/s, Read: 4MB/s
    128 – Write: 2MB/s, Read: 14MB/s

    No noticeable differences in speed.

    Reply
  • Avatar of weehooherod

    The number you reverts when you restart your phone. If you use CyanogenMod 6 or 7 then the value is changed to 128 and always stays there.

    Reply
  • Avatar of Trent

    Sweet! I think this fixed my horrendous music playback issue of constant stuttering. I nearly went back to my iPod (and had a Verizon iPhone in my future) because of this. This is a big enough black eye on HTC, in my opinion, to make me think really hard about whether my next smartphone is even from HTC at all, but I’m glad some ingenious hacker found this fix. Thank you, thank you, thank you. My music was unlistenable, and I had no idea why.

    Reply
  • Avatar of MildlyDisturbed

    You can also just install any of the Netarchy 4.3.2 kernels, fix is built in, or the newest Sprintlovers ROM, several other roms have it built in I’ve read

    Reply
  • ES Explorer won’t work either. Seems like Root Explorer is the only one that works.

    Reply
  • Of course I’m using Root Explorer.
    It works now, but my 16GB card (brand new) and my 8GB cards have nowhere near the gain other members are seeing. Weird. Oh well. Google doesn’t support Apps business partners either, so, welcome to Android.

    Reply
  • Avatar of Coiledwire

    Sweet. Running a stock, rooted EVO with a 16GB class 2 SD. Got a large jump in read speed based on the SD speed app.

    with 4: write = 6MB/s, read = 5MB/s
    with 128: write = 6MB/s, read = 14MB/s

    Not sure on real-world gains, but the numbers make me happy anyways. Too bad I need to remember this every time I reboot the phone.

    Reply
  • Using a Class 4 SD card, read speeds went from 5 to13mb. Thank you devs for the tip!

    Reply
  • Avatar of mildlydisturbed

    I honestly think when they were writing this they were writing everything for stability and to get it out the door asap with the expectation of putting speed and battery life in later.

    Reply
  • Avatar of mildlydisturbed

    You’ll only notice it on loading things from the SD card (gallery, pictures, applications you moved to the sd card)

    Reply
  • I am rooted but have not loaded any new Roms so I’m still running the stock HTC Rom and my Write speed is 2mb and my Read speed is 8-9mb. I’m using the stock 8gig microsd card, class 2.

    screenshot: http://cl.ly/2r3a1X2r3a1c1l0I2g1O

    Reply
  • I haven’t done this mod yet, and my read speed is 9.2mb/sec, that’s great but my write speed is only 2.2 on a stock rooted rom. Are this numbers right? I’m using the card that came with phone.

    Reply
  • Avatar of scholarlv

    ES File Explorer works only if you change the permissions on the file first. What i’ve done is use SuperManager with root permissions of course and changed the permissions to r/w owner/user/group. Then use ES File Explorer to edit the file.

    Reply
  • Avatar of mranderson

    file explorer works and its free, and it does the same if not more than root explorer. the best part, besides being free is that there are no ads, and you can edit any file you want, just be careful you don’t brick your phone.

    Reply
  • Avatar of mranderson

    its file expert, not file explorer.

    Reply
  • If I’m buying a new SD card … should I get class 4? 6? 10?
    What does the Evo hardware actually support?

    Reply
  • i’m using san disk 16 card think they are rated 4…..i already knew of this from xda but my write speed is 7.1 and my read is 18.2. At present time i’m running 73 nightly cm7 with tia 4.002 kernel. i’ve got a 32 san disk card that is formatted and clean but to be honest i’ve found that 16gb is ALOT. If you fill one up odds are you got alot of stuff you don’t use. My 16 has like 10 or 12 roms and tons of kernels and such and i very seldom use alot of em now. I do keep my nandroid from amon ra cleared off pretty good though. Most anytime i upload anything i clean off my backups. Those things take up a ton of room.

    Reply

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