It is apparently possible to revert your PS4 to its previous firmware version, without any backup

This is probably one of those “so obvious nobody talks about it” things on the PS4 scene, but it’s only come to my attention right now. And to me, it is a big deal, but maybe I’m just late to the party.

TL,DR: Your PS4 keeps a working copy of its previous firmware (for emergency backup reasons) and it is possible (but difficult, as in, hardware sills required) to go back to it, without any other kind of backup or preparatory work. In other words, if you’re running e.g. on firmware 9.03, and your firmware before that was 9.00, it might be possible for you to come back to 9.00.

PS4 Downgrade to previous revision – The context

We recently wrote an article about Modded Warfare’s lengthy and detailed tutorial on how to “Downgrade”* a PS4. The process is very heavy as it requires hardware skills, and, more critically, preparatory work while you’re at the desired firmware. A typical situation would be to prepare a backup while you are on a jailbroken firmware (e.g. 9.00), then intentionally upgrade to the latest firmware (at the time of this writing, 10.01) in order to play online, and then go back to 9.00 (for which you had prepared the backup) later on.

Bottom line, most people looking for a PS4 Downgrade online will not have prepared such a backup, and are most likely already stuck on a high firmware by the time the learn about this technique.

Modded Warfare’s video re-kindled discussions on PS4 downgrades in the scene, and it came to my attention (thank to @Mohamme80484363) that a method to revert back to one’s previous firmware is basically possible with the same technique, except without the need for a backup.

Here’s why:

When you install a firmware upgrade on your PS4, the PS4 has a mechanism to “revert” (here’s that word again) to the previous firmware, in case anything goes wrong. For example, if I’m on 9.60 and attempt to install 10.01, but then the power goes off in the middle of installation, the PS4 can easily go back to firmware 9.60 (actually, it probably never went to 10.01 in that scenario, but you get the idea).

(I’m assuming a similar mechanism is used when reverting from a Beta Firmware to your previous firmware, by the way)

Modded Warfare touched on this in this video (and he credits Centrinouk  LightningMods for the explanations on that): The PS4 constantly keeps 2 firmwares stored in different locations of the hard drive, and the syscon chip has a pointer to your current version.

This is a very abstract view, don’t quote me on this picture

By overwriting some specific values in the Syscon chip, it appears to be possible to revert to your previous firmware. This of course only works for that one specific previous firmware, for which your console kept an “emergency” backup. And it requires writing on the syscon chip as well, which requires pretty much the same hardware and skills as the technique described by Modded Warfare.

Modded Warfare described this partition mechanism in his video

BetterWayElectronics, whose tool PS4 NOR Validator is used in the process, also mentioned:

This is done much easier with the help of my latest software. With it you can patch the Syscon and NOR to downgrade to the previous CoreOS slot, so whatever firmware you had prior to updating you can flip back to it. This also allows Service Mode switching and other neat tricks. You can also repair LoadBios errors. I think this guide is quite a useful thing for repairers to learn from, but I must say that my methodology to dump/patch/write the Syscon is infinitely easier and quicker, no need to edit/trim any files etc. I will be making a guide soon enough but I doubt I could ever make it to the same quality as this one. I really should learn… Anyways, you can dump the syscon on board if you simply want a backup and nothing else. As for programming the new syscon you can do it with TTL but you have to remember to remove the security that was originally in place, otherwise your new chip will be just as locked as the original. My program will validate the syscon, patch it and remove the security all in one. We are also working on removing the need for a new chip also, so the entire thing can be done without removing the chip eventually (hopefully). So in my opinion I would hold off on using this guide as it is very superfluous and intimidating for those new to this whole thing.

Hacker Darknesmonk on Russian scene website 4pda.to shared very specific details: (based on research from vlab.su)

All revisions with A0X-COLX chip are available for downgrade: (X any number)
(FAT 10,11,12; SLIM 20,21,22*; PRO 70,71,72*)
SLIM 22XX with SAF-003 and PRO 72XX board chip “SIE INC” WITHOUT A0X-COLX inscriptions cannot be downgraded.

How to find out your previous version of the software:

•  In notifications, see the update history (if you did not clear the log)
• There are cases where the second firmware slot is already occupied by a pending firmware, in which case you won’t be able to downgrade

The downgrade itself is similar to what is done in Modded Warfare’s revert, in that you have to either overwrite the syscon, or replace it. Where it’s different is that you only have to replace a few values, instead of work with a full backup. The hard drive, also, remains untouched.

Although the hardware skills needed remain quite high, the obvious benefit of this technique is that it doesn’t require to have prepared a backup beforehand. It might be useful to people who mistakenly updated from 9.00 to a higher firmware.

I however remain convinced that (today) a much safer (and in many cases, cheaper) way to get a Jailbroken PS4 is to buy one. Which is not to say this isn’t super interesting information!

As you can see this thread on 4pda.to is already several months old, and according to Darknesmonk, it has been an open secret since Fail0verflow revealed their syscon hack back in 2018. Did I just miss this entirely? It’s likely (let me know in the comments if I’ve just been blind to something that’s very well known in the scene!)

All the details are here (in russian but google translate is your friend)

* Some folks on the scene really, really don’t like to call it a Downgrade, and prefer the word “Revert”, to really emphasize that you can only go back to a state that your console has been in before.