[Galaxy Tab 7.7 Q&A, Help & Troubleshooting] Milan Kerslager:
There seems to be TRIM (or flash handling) bug in official firmware [SOLVED]

I had official ICS 4.0.2 firmware on my Galaxy Tab 7.7 phone (GT-P6800), but it becomes slow and sluggish and I was unable to do anything. Even popping up screen to accept phone call was so slow, the caller hang before I was able to do. Also writing on touch keyboard was really slow and unusable.

I tryed to reflash, I tryed Slim version of official firmware too with no luck. The system was faster, but even no apps were added (just system update through Google Play), the responsibility of the system become sluggish again (and even worse than before).

Then I recognized that even I pick firmware reset from CWM or from Settings (in Android system), my internal flash memory is not deleted and many (hidden) files remains there (one may think that internal flash was empty, because hidden files are not normally shown). As I had some applications making A LOT of (hidden) files (maps, geocaching, etc), the clues become visible to me. [I tryed to do factory reset from system and from CMW too, so there could be bug too]

To make story short, I manually deleted all files in internal memory (by running "My files", tap on Menu, and pick "Show hidden files"). This takes LOOONG and then the system become more usable, but still not enough.

And yes. There is legendary TRIM command which makes flash memory to know what portion of the flash memory is free to use. Without that even one deletes files, the flash itself does not know that the place is really free and keep data on it. When TRIM command is used, the internal FTL (Flash Translation Level) system in flash chip can use place marked by TRIM to spread writes and wear level writes to not destroy some parts of flash with excessive number of writes (they are limited to 10-100 thousands times or so). The TRIM allows FTL to breath. So what now? Android officially support TRIM since 4.3, but there is no 4.3 version of Android for Galaxy Tab 7.7 at all, only 4.1.2 (but only for East Asia officially). But this is better than nothing. Maybe Samsung put some support to 4.1 (backport?) as Samsung do for other features or (maybe) fix some other issues related to flash support? I don't know...

Then I decided to go to 4.1.2 from from here and wrote some info to the Wiki. And I reflashed, deleted cache, Dalvik cache (from CWM), then I fill up space in internal flash memory and then deleted all files from "My files". And viola! The speed is incredible again :)

To the end - maybe it is not necessary to go to 4.1.2, maybe just make sure you delete all files (including hidden ones). But I does not care about it. I have KIES_HOME_P6800DXMD3_P6800OLBMD3_1157844_REV00_user_low_ship.tar from URL mentioned above (no M3D DEODEXED was put on top of it). This is East region stock firmware and I happily use it in central Europe (SMS, normal call works, MMS was not tested yet). The only thing that seems to not work is support for 5GHz Wi-Fi (I don't see it in Wifi Analyzer) but I do not care and I'm enjoying full speed of my 7.7 again :) Sorry for long post. Just FYI.

---------- Post added at 12:22 PM ---------- Previous post was at 12:14 PM ----------

This happens when Dalvik cache contains data about more recent applications (ie. you install one with older time mark than was before). You have to go to CWM and delete Dalvik cache (in Advanced menu). As I wrote below, there could be bug even in CWM so you may want to try 6.0.3.0 (I have this now) see link.