The recently released jailbreaks, Corona 5.0.1 Untethered and Redsn0w 9.10b1, are compatible with A4 devices like iPhone 4, iPhone 3GS, iPad, iPod Touch 4G and iPod Touch 3G. But both the jailbreaks don't have a bootrom-level exploit which could jailbreak the A5 devices.
There are two major differences between Apple's A4 and A5 processors. A4 processor was built upon ARM's Cortex A8 CPU which was a single core CPU, but the latest, A5 processor, is built upon ARM's Cortex A9 dual core CPU which is the biggest hurdle in finding the bootrom-level exploit in both the A5 devices.
The second biggest difference is the Graphics Processing Unit (GPU). In A5, the Cupertino-based tech giant used Imagination Technologies' PowerVR SGX543MP2 dual core graphic processor whereas it used PowerVR SGX535 single core of the same company in A4.
After releasing the untethered jailbreak for A4 devices, Chronic Dev-team's French member Pod2g has again indulged himself in finding the bootrom-level exploit for the A5 devices.
He had already achieved some success in his efforts as he found something related to A5 cache.
I'm close, but I can't figure out what happens. It certainly has something to do with the Cortex-A9 cache management, Pod2g said in his blog.
Before the release of the untethered jailbreak, Pod2g had given the testing responsibility to the Chronic Dev-team so he could focus on A5 jailbreak.
Pod2g in his post wrote: I read the comments on the blog, and I know that a lot of people are waiting for the A5 jailbreak. I gave all the details to the chronic dev team so that can finish, test, integrate and release the A4 JB ASAP. I'll put all my energy from now on the A5.
However, the untethered jailbreak is out and people using A4 devices can go ahead and enjoy the exciting new applications available on Cydia.
Before running the latest untethered jailbreak from both the Dev-teams, you should know some facts about the jailbreaks, which can help you have a silky jailbreaking experience.
1) The latest jailbreaks, Corona 5.0.1 Untethered and Redsn0w 9.10b1, work on iOS 5.0.1. So update your devices to iOS 5.0.1 if you are still stuck with iOS 5.0.
2) This untethered jailbreak will work only if the device is powered by A4 processor. iPhone 4, iPhone 3GS, iPad, iPod Touch 4G and iPod Touch 3G are the devices which can be jailbroken with Corona or Redsn0w 9.10b1. This jailbreak will not work on A5 devices like iPad 2 and iPhone 4S because a bootrom-level exploit is yet to be discovered by any of the hackers.
3) If you have an already tethered jailbroken A4 device, then you do not have to go for iPhone Dev-team member MuscleNerd's Redsn0w 9.10b1. All you need to do is just go to Cydia in your jailbroken device, search for the jailbreak released by the Chronic Dev-team's French member, Pod2g, by typing Corona.
Once you find Corona, download it and run it after installing and your device is untethered jailbroken now.
4) If you are jailbreaking your device for the first time, then you need not to go for a tethered one. You can directly download Redsn0w 9.10b1 and run it in your device to jailbreak it. Redsn0w 9.10b1 has Corona packaged inside, so you don't have to go for two different procedures to get the untethered jailbreak.
5) There are many reports of the jailbreaking going wrong and if you are not familiar with jailbreaking, then we advise you to back-up all your data before going for the jailbreak. It saves your valuable data in case the jailbreaking goes wrong and your device needs a restore.