Excuse me for my bad english.
Yesterday my Asus sabertooth z77 started to showing off 4GB of RAM instead of 8GB.
I checked every RAM DIMM and they works on every DIMM slots.
I downloaded the latest BIOS available for my mobo from official website and updated to version 2104 but the problem persist.
Today I noticied that on BIOS interface on "ME version" it says N/A. I tried searching online and reading this forum but I could figure out a proper step-to-step guide to fix it due to my noobiness regarding bios modding.

Resume:
1) MOBO: Sabertooth Z77 with latest bios 2104
2) ME version : N/A (it is corrupted right?)
3) Tried MEInfo and it says Error on communication with ME module
4) BIOS and Windows uses 4GB of RAM instead of 8GB installed (also it shows that ram are 1333Mhz when the proper frequency is 1866Mhz)

Right now the PC is unloaded of hard drive. I am open to install every Windows version (if there is a compatibility issue) or linux.

Thanks for your support.

I want to add that I am trying every Intel Managment Engine Interface + Intel ME Firmware Upgrade available on ASUS website but:
1) I am trying different O.S (Win7 to Win10) but all of them are unable to install the Intel ME Interface
2) Intel ME Firmware Upgrade tool can't be used without interface installed or due to corrupted ME can't fetch the current ME version installed (a pre-requesite of the upgrading tool is to have v8 installed)

@Pollo123 - If ME FW is corrupt you only have two options FPT with unlocked FD first either via programmer or pinmod, if a BIOS reflash does not fix it. Or you can use a hardware programmer such as CH341A. No ME Update or ME FW Update tools will work when ME FW is corrupted
Did you already try to reflash the BIOS? If not try that now, and once done load optimal default (This is standard procedure, not meant to affect ME FW)

Yes, when you see ME N/A or 0.0.0.0. it's corrupted. 4GB instead of 8GB ram is usually nothing to do with ME FW, but I suppose it's possible (I've never seen this as the cause in 10 years though)

Here is how to pinmod the board to unlock FD, see E1
[Guide] Unlock Intel Flash Descriptor Read/Write Access Permissions for SPI Servicing

Before you do that, get all this ready on your desktop or on a USB DOS Stick - download ME System Tools package V8 from section "C"
Intel Management Engine: Drivers, Firmware & System Tools

Inside you will find Flash Programming Tool folder, and inside that a Windows folder. Copy the ME.bin file from link below into this folder. Then select that Windows folder, hold shift and press right click, choose open command window here (Not power shell).
Then to flash the ME FW - FD must be unlocked first via pinmod, Command prompt must be Admin (hence the method to open above), and ME drivers must be installed first. At the command prompt type the following command to flash the ME region, >> FPTw.exe -me -f ME.bin

If using DOS Version, copy the ME.bin file to the root of a USB Bootable DOS stick (not in any folder) and then copy all files from the DOS folder (the one inside Flash Programming Tool folder) to the root of the USB also
Then at DOS Prompt >> FPT.exe -me -f me.bin

If you don't want to do the pinmod, you need to order CH341A flash programmer or other similar flash programing tool and a U Type Flat IC Chip puller / extractor

Or!! I can also make you mod BIOS, that may reflash the ME on BIOS update via USB Flashback, you may need to USB Flashback that BIOS and then afterward reflash it again via EZ Flash (Or also try FPT Flash then after this too, to see if the change I make allows FPT reflash)
Here is that BIOS - first, flash this via USB Flashback, then boot to BIOS, load optimal defaults, reboot back to BIOS and check ME version, if still ME N/A, go to EZ flash within the BIOS and update again to this BIOS again if EZ Flash will let you, if not reflash once again with USB Flashback.
Then reboot and check ME FW again on BIOS Main page, if still N/A, then try FPT flash from DOS or windows, if you get error that it's locked then this method will not work and you'll only be able to fix using the methods described above

Never mind mod BIOS, you can do it this way, to test the above method - see this guide (for an unrelated change) but will show you how to use and boot to grub - [GUIDE] Grub Fix Intel FPT Error 368 - BIOS Lock Asus/Other Mod BIOS Flash
You need to rename the .efi file to Shellx64.efi And your variable to change is 0x27A
So at grub prompt you will type the following >> setup_var 0x27A 0x1
Then control-Alt-Del to windows or DOS and try the FPT flash again.
If this fails, and you go back to grub and do it over again, and it's reset back to 0x0 then I'll have to make you BIOS mod, but this method doesn't always allow this anyway, so that's why I give you this way to change it first instead of mod BIOS flashing.

Here is that mod BIOS just in case you end up wanting to try it
http://s000.tinyupload.com/index.php?fil...205964051318137

I successfull installed your modded bios, but iI can't find the link for the ME.bin that you mentioned.
From the ME Thread, Should I download "Intel ME 8 1.5MB Firmware v8.1.70.1590" or "Intel ME 8 5MB Firmware v8.1.72.3002"
I don't know which size can contain the chip.

Thanks you.
I successfull rewritten the ME using your modded BIOS and using FPT.
I used the 1,5MB firmware.

The only issue is that the ram frequency isn't detectec automatically, I manually set it and it works fine.

Thanks again for your support!

@Pollo123 - you're welcome, and sorry about that! You should not use any random 1.5MB FW, even the ones provided here in the ME FW thread, you need to use the one extracted from the BIOS I sent since it has board specific things programmed into it, or use the BIOS file itself as source and tell FPT -me -f biosfile.bin
I can't believe I forgot to link the ME.bin I extracted for you Here it is now in case you want to redo things if you used stock/generic ME FW without board specific settings >> http://s000.tinyupload.com/index.php?fil...665112947970828
Glad you got it working now, but if you didn't use your BIOS as the ME source, then you should redo so it's working properly and does not cause you issues later.

Thanks again for your support.
I successfull installed the proper ME.
It has been a downgrade from latest ME available for my chipset to very old one!
Asus doesn't update things very often.

Just a bit of curiosity:
I am a Computer Sciente Universitary student and I would like to know how did you mod the bios to allow written permissions.
If I read well, my MOBO uses a special type of extension .CAP that should be protected (?)
Did you manually flip the flag that you mentioned in the grub method using Hex editing?

@Pollo123 - You can take your BIOS with old ME in it, update it via the clean/update ME guide here to latest version, then extract that from BIOS via UEFITool, then flash that in via FPT again.
Or, since ME is working now, you can download latest ME FW .UPD version from the main ME FW thread here, and use ME FW Update tool to update to that version.

Asus, and some other companies use .CAP (en/capsule/encapsulated file) as a security measure to protect the actual BIOS file itself, it's in front of BIOS (usually 2KB or 4KB) This is like a key to a zip archive as a cheap example, or a secure envelope.
This is processed at time of flashing, BIOS extracted and the capsule set aside/not used after that, it's not part of the actual BIOS. It is protected, if I give you a modified .cap file, the normal BIOS flashing method provided by Asus (EZ Flash or AI Tweaker, will not take that edited file due to broken security)
When you do FPT flashing, there is no capsule used, since we aren't using that BIOS with capsule, you're dumping from the actual onboard chip and or flashing to the onboard chip using BIOS or files that do not have a capsule on them (ie I removed capsule/extracted BIOS).

On the ME allowing, I simply changed the actual BIOS setting for "ME Re-Flash" to enabled, to allow ME Reflash via BIOS update processes or FPT flashing.
This is stored in two locations with in the BIOS, at NVRAM and at Setup module, changes made via AMIBCP BIOS tool for the NVRAM setting, setup module edited w/ UEFITool with IFR Extractor and hex edit