yeah, I believe the bootloader (the black screen that handels the update) is never touched (which is a good thing, it should make it pretty much impossible for firmware updates to brick the devices since the bootloader will always be there to handle things).
Yea, I've dumped the bootloader before using a F2A adapter. Never got much farther than that because I couldn't use it to write the bootloader back*.
So the white cards only have a bootloader that can't read sdhc cards, but the 1.75+ kernels flashed onto it will be able to use them for ROM loading. That means that updating will always require a non-sdhc card while you can load roms from higher capacity SDHC cards.
Far as I can tell, there's a minimal of at least two versions of the bootloader. One can read SDHC and one can't. Also, the one that can read SDHC actually has a blue on yellow line at the bottom "fat initial 1" while flashing/upgrading. This later version is actually bad for one major reason: it'll erase your kernel before actually checking if there's an ezfla_up.bin there. So, yea, great way to temporarily brick it. :/
In any case, this is true even though I've got two EZ IVs with the same revision (bought at the same time): EZ402 2006.03. Not sure if that's when they changed over the bootloader or merely never updated the silk screening. In any case, the board that doesn't read SDHC in the bootloader also doesn't properly work with my Sandisk Extreme Plus 16GB card UHS-3 (has issues booting + can't seem to read the card). It's also slower to load games than my Kingston 2GB card. Although that's also just an across the board problem with later firmwares, it's true when I temporarily updated the kernel to 1.78. But back to 1.74 for that slightly faster speed.
On a somewhat unrelated note, I even got around to actually trying out the 2.x kernels. Looking at the .pat file and it's clear that it's not an actual patch file per se. It looks to be offsets into the rom (hard to be sure on that). Having said that, it really doesn't look like it's merely using a version of dwedit's/my fork of dwedit's sleephack patcher because it seems to reference a lot more addresses. Again, it's hard to be sure if that's the case on what's going on. It might be also do save patching for all I know. *shrug*
In any case, what would obviously be awesome in a future update would be IPS patch support. It has the advantage of being (1) very trivial or (2) covering ~16MB which should cover all the PSRAM games. Definitely, though, I don't see a way of overriding .pat in some fashion to make it IPS like or otherwise a general patcher. A shame, too, as I'd be a lot more tolerant of using the newer kernel if I could actually use clean ROMs.
A second suggestion (if IPS patch support was added) is some primitive symlink support (a specially named txt file pointing to the original ROM). That'd allow for ROM hacks without nearly as much wasted space.
* Some time ago I bricked my EZ IV (was trying to add LZ77 support) and was trying to recover it. I ended up buying two EZ IV replacements after I gave up on that endeavor. I'm not even sure if I still have the bricked one still around.
