Lenovo A806 ROM flash readback

The phone arrived from China with a buggy altered firmware:
Hardware : MT6592
Model : Lenovo A806
Build number : VIBEUI_V2.0_9432_ST_A806
Build date UTC : 20140807-112632
Android  v : 4.4.2
Baseband v: A806.V30, 2014/07/31 14:53
Kernel v : 3.4.67 (buildslave@xmws58) (gcc version 4.7 (GCC) ) #1 SMP  Thu Aug 7 19:24:27 CST 2014

To backup the original firmware you need:

1) Preloader driver for MTK
2) MTK droid tools
3) SP flash tool

Backup process:
1) Get scatter file with MTK droid tool and phone switched on, debugging enabled
2) Eject the cable, power off the phone, eject the battery
3) Open SP flash tool, select the scatter file, go to the "Readback" tab, add new, put the number from the "Cache" partition start into the "Size" field.
4) Press "start readback", insert the battery, attach the cable.

I got a 1.4GB ROM file in 32 minutes.

http://www.theandroidhow.com/2014/05/how-to-backup-rom-dump-mtk-android.html
http://forum.xda-developers.com/showpost.php?p=44509214&postcount=407