[Kindle Fire HDX 7" & 8.9" Q&A, Help & Troubleshoot] draxie:
First brick!

Interesting, thanks!

That's an odd and potentially fatal glitch.

Just for curiosity, was there any other disk-intensive activity going on

or other connected USB devices in heavy use at the same time?

That's pure gold actually. The device entered 'download mode'.

You should be able to "flash" (i.e. directly overwrite) *any* partition.

This is exactly how we managed to fix those 2 devices recently...

BUT: care must be taken! I've just produced what I believe is my

very first brick yesterday... Amazingly, I still keep learning new tidbits;

sometimes the hard way.

The HDX in 'download mode' is NOT visible _at_all_ under MacOS.

The 'dd' command under Linux needs 'oflag=direct' to get data

*correctly* written to the EMMC. I've tried several times without

that and always ended up back in download mode, but I knew

this had to work (since we've managed to do this from Windows);

so, I kept trying. [Unfortunately for me, I got lazy and only flashed

'aboot' and not 'recovery' with the right option...]

Power+VolDn to enter 'fastboot' mode only works with *unlocked*

bootloader. I had thought that the vulnerable version supported

that even when locked, but NOPE. Now, I have an Apollo with the

vulnerable bootloader that I just cannot get into 'fastboot' mode.

(It gets stuck at the gray logo [probably trying to load the old kernel

and/or recovery, which are likely both there]; nothing on USB.

I'll need to find that post about HW-hacking to access the EMMC;

otherwise I just got a really expensive new battery for my trusty

old Apollo... --- if you happen to know about a better way to

recover from this, do let me know! ;^P)

I tested the procedure "the right way" with my other(Thor) test device,

and it worked as expected. (I also got confirmation from ONYXs.)

Contrary to one of my earlier posts, I ended up using 'adb sideload'

to get the ROM flashed from TWRP. [BT W, I've also learned that

contrary to the stated prerequisite in the OP for CM14.1, you don't

need an unlocked bootloader, it suffices that a vulnerable version

is installed (they probably cube-sign their boot.img).]

Expect a post with the new method "sometime soon". (-;

Lucky you! Your bootloader had, of course, been unlocked...

AND, the glitch didn't affect it. Which seems to indicate that

-reassuringly- '[emergency] download mode' is triggered not

only by a missing or damaged bootloader, but possibly other

severe error conditions as well...

BTW, did you have to press Power+VolDn to get into fastboot?

Right, that's nice when you have an unlocked bootloader,

or a vulnerable bootloader and a "fake-signed" TWRP;

won't work otherwise...

I agree. Flashing CM-style ROM:s shouldn't touch recovery;

so, even with the glitch (some alpha particle, perhaps), that

"should" be intact.

Strange, indeed!

---------- Post added at 08:29 ---------- Previous post was at 08:22 ----------

Actually, the "new" streamlined method I mentioned

doesn't need root and doesn't care about the version

of FireOS installed. All you need is a 'fastboot' prompt

(which you can easily get from 'adb') and dd for Windows.

[MENTION=8087953]bluecoyote[/MENTION]: PM me if you want to test-drive...