Upgrade 3GS old bootrom from 4.1 to 4.2.1

[EmailGuy]

I have an iPhone 3GS with the old bootrom that is jailbroken on 4.1. I've started to find some apps that now require 4.2 and I'm considering upgrading and then jailbreaking with Greenpois0n.

What is the baseband version in 4.2.1? I'm currently on the 5.14.02 baseband. Does 4.2.1 use the same baseband or newer? I don't need an unlock right now because I'm on AT&T, but it would be nice to preserve the option to unlock. I don't believe there is an unlock for 5.14.02 now, but there may be in the future.

Since I have the old bootrom, I've had an untethered jailbreak available for some time now, but until apps in the app store have started requiring 4.2, I never had a reason to upgrade.

I upgraded my iPad to 4.2.1, but it is WiFi only and I wasn't worried about the baseband.

[Simon]

It is 5.15.04 on 4.2.1. No need to preserve though as both 5.14.02 and 5.15.04 cannot be unlocked (at least not without updating to the ipad baseband).