EDIT: I am now using this with JM2.
With this fix you should get Quadrant benchmark results of 1400+ (depending on the SD card used). It is an alternative to the NAND fix and, apart from the speed increase, you can determine the space available for application memory yourself:
This is how i did it:
Part 1: Prerequisites
1. If not already rooted, do so before starting:
2. Make sure ADB is working on PC. [Install using these instructions if you don't already have it:
2. Make sure BusyBox is installed.
Part 2: SDHC card
1. Inserted my class 6 micro SDHC card into PC [u can use any size/speed SDHC]
2. Downloaded Paragon Hard Disk Manager [NB: Trial version didn't work for me]
3. Using my PC and Paragon, i created a 1GB EXT4 partition on my card [you can also use EXT3]. THIS MUST BE THE SECOND PARTITION; THE FIRST SHOULD BE FAT32.
Part 3: Flash the kernel
1. Downloaded the v4 (ext4) .tar file from the above link (on my PC)
2. Started up Odin3
3. Inserted SDHC card into phone (and removed SIM).
4. Put phone in 'downloading mode' [volume down + home + power]
5. Connected phone to PC [you should now see one of the COM's in Odin]
6. Chose only the PDA part and attached the downloaded v4 tar [NB: do NOT touch any of the other options]
7. Hit 'start' and waited ca. 15 secs for process to complete.
Part 3: Create symlink to the ext3/4 partition on the sdcard
1. Put phone into debugging mode [Settings -> Applications -> Development -> USB debugging]
2. Connected phone to PC
3. In CMD, typed:
su [NB: may need to accept superuser request on phone]
busybox cp -rp /data/data /disk/
busybox mv /data/data /data/data.bak
busybox ln -s /disk/data /data/data
busybox mv /system/media /disk/
busybox ln -s /disk/media /system/media
2. Installed Quadrant Standard and did a speed test (see attached pics):
NB: IF ANYTHING GOES WRONG AFTER APPLYING THIS FIX OR YOU SIMPLY WANT TO UNDO IT, JUST REFLASH FIRMWARE. i myself tried removing the sd card to test what would happen. stupid me, lol!