What does the "Memory Clear" functionality mean in ASUS motherboards?

Question

In my MB's UEFI settings, there's this option called Memory Clear, under North Bridge Settings. Possible values are Enabled and Disabled.

Some models featuring this option:

• ASUS CROSSHAIR V FORMULA-Z
• ASUS SABERTOOTH 990FX and newer
• ASUS M5A99FX PRO / EVO and newer

The following is a screenshot taken from the SABERTOOTH 990FX R2.0 motherboard:

What does it do exactly? The Motherboard's manual is not useful when it comes to details like these.

Solution 1

According to the user manual, Warm Boot RAM and Memory Clear have opposite effects. It is tough particularly with ASUS as usually the manuals are poorly translated to English.

Warm Boot RAM will maintain the data in memory on a warm boot (reboot).

Memory clear explicitly empties the data in RAM (zeroes it I would imagine).

Solution 2

Cold boot is when the computer it booted after it was completely shut down. Warm boot can only be initiated from Windows by doing Restart.

The differences between warm and cold boots are:

1. Warm boot does not do POST and is therefore faster.
2. Shutting down (cold boot) cuts the power to memory, which would clear the RAM (if Windows does not elect to do Hybrid sleep).

I agree that Memory Clear probably zeroes the memory so that there are no left-overs in RAM from the previous boot. This is a security measure to ensure that sensitive data, such as password, cannot be retrieved by a virus immediately after the boot terminates. It will of course slow down the boot in proportion to the amount of installed RAM.

Warm Boot RAM probably means "RAM contents are left as-are during boot".

This explains why the manual states that Warm Boot RAM and Memory Clear have opposite effects.

[EDIT]

The Asus manuals, for example the SABERTOOTH 990FX/GEN3 R2.0, describe these options as :

Warm Boot RAM [Enabled]
Allows you to enable or disable the re-use of data in the RAM after a warm boot to speed-up the boot process.
Configuration options: [Enabled] [Disabled]

Memory Clear [Disabled]
Allows you to enable or disable the Memory Clear function.
Configuration options: [Enabled] [Disabled]

This confirms my remarks concerning Warm Boot RAM.

For Memory Clear, I found this brief remark in the Asus forum (so admittedly it is not in the manual):

Memory clear is just the opposite of the warm boot option. power down Enabled allows the memory to shut it self down When ECC mode is enabled as an emergency feature

I believe that Memory Clear is "the opposite" as regarding boot-speed, slowing down the boot which Warm Boot RAM is supposed to speed-up. In any case, it destroys the RAM that Warm Boot RAM is supposed not to destroy (although preserving it is useless to anything other than a virus).

Comments

[Ƭᴇcʜιᴇ007]

Just for completeness, exactly which model of Asus motherboard are you using?

[Yorik]

I am making an educated guess (so I cannot directly answer) that this is a function that clears memory on boot. It is a security measure: it is plausible (but difficult) that a program can extract data from memory that was "set" during the previous session. See: "data remnance cold boot attack"

[Yorik]

See also: security.stackexchange.com/questions/10643/…

[Wouter]

This is my best bet: encyclopedia2.thefreedictionary.com/clear+memory And @Yorik has provided a possible reason why you would want to do this. But if you realy want to know, you will have to contact ASUS. Can't find anything about it online...

[Daniel B]

Wow, these two options sure are a load of bs. xD Speed up boot by leaving data in RAM, yeah right.

[Marc.2377]

Hi. For completeness, would you be willing to provide some citation? Thank you.

[Marc.2377]

Unfortunately the motherboard's manual doesn't actually seem to contain that statement...

[harrymc]

@Marc.2377: I found that statement in the manual of one of the motherboards mentioned in the post, just cannot remember which one or where.

[Marc.2377]

It would be awesome if you manage to find it and update us

[harrymc]

I added my findings in the answer.