These models do not work with OS6, because they have 32bit processors, and OS6 is only 64bit.
Instructions courtesy of AMRivlin and chirpa
For more detail, please see the following forum threads;
A ready made downgrade image (RAIDiator-x86-4.2.xx-downgrade) is now available: https://mega.nz/#!STgTGCBK!FmxBsvQeJTr6qQ0mBRH1AFRQg87TQlCN_roCM3ZqZzk
If you want to make your own image basically you will need to download an old RAIDiator release, and modify the header, such that the currently installed OS thinks it is newer, or it will not allow a downgrade.
Instructions (to be run from a Linux system, or directly on the NAS itself).
$ wget -q http://www.downloads.netgear.com/files/GDC/RNDU2000/RAIDiator-x86-4.2.24.zip $ unzip RAIDiator-x86-4.2.24.zip Archive: RAIDiator-x86-4.2.24.zip inflating: RAIDiator-x86-4.2.24 inflating: RAIDiator-x86-V4.2.24_ReleaseNote.html $ head -n1 RAIDiator-x86-4.2.24 $ echo -n 'info::name=ReadyNASOS,version=6.2.0,time=1372729316,size=56387584,md5sum=5a29e74205983247ba50358a453c9ef2,arch=x86_64,descr=ReadyNAS Final Release,release_notes=http://www.readynas.com/RAIDiator_x86_4_2_24_Notes' > newhead $ dd if=newhead of=RAIDiator-x86-4.2.24 conv=notrunc 0+1 records in 0+1 records out 209 bytes (209 B) copied, 0.000162523 s, 1.3 MB/s
So basically what we have done, is modify the header, which is only used by the installed OS version to verify if the image is valid, to make it think it is installing a newer version of itself. The fields we have changed are name, version and arch.
You now upload the image to FrontView on ReadyNAS OS6, and it should accept it. After update and a reboot, you need to do factory default in boot menu. A few minutes afterwards, you will be running RAIDiator 4.2 again and you can recreate your storage.
Retrieved from http://netgear.nas-central.org/wiki/OS6_on_Legacy_x86