There are official kernel V1.56 and non-official kernel for R4 Ultra / R4i Ultra. R4i Ultra 1.4.1 fw for NDSi 1.4.1 available on Sep 25th, 2010.
R4i Ultra kernel update is relative slow but it is still on hot sale, which is mainly coming from the third party kernel compatibility. Users can install modified kernels of their own.
Any kernel below will do for R4i Ultra or R4 Ultra card.
(1) R4i Ultra AKAIO 1.8.6a Kernel (Same as R4i Gold V2.0T AKAIO 1.8.6a)
(2) R4Uys and Patch (Chinese, AKAIO-1.7)Download both of them, then the unzipped are required to be installed into the root directory of memory card.
(3) Use R4i Gold V2.0T Kernel from www.r4ids.com
(4) R4i Ultra / R4 Ultra Kernel YSMENU 2013-10 (compatible with more latest games)
(5) R4i Ultra / R4 Ultra Kernel AKAIO 1.5.1
(6) DahongR4_v2.1 (This kernel is personally edited, download available after register at tvgame360, updated on Oct 10th, 2012 )
If you have any question about the use of R4 Ultra Kernel, pls feel free and send your e-mail to us. R4wood.com will respond wthin 24 hours.