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Asus RT-AC56U - Overclocking ARM CPU

Rating: 15 votes, 4.47 average.

1. Navigate to

2. OverClock: run in the cmd window, copy paste/enter:
nvram set clkfreq=1200,800
nvram commit && reboot
- this will set CPU clock to 1200MHz and memory to 800 (for comparison - the stock is 800/533)

nvram set clkfreq=800,533
nvram commit && reboot
Warning: your router may hang at this point. Let it stay for couple minutes, if it does not come back, power cycle.
If you cannot get the router back after power cycling, follow to restore procedure outlined above.

3. After successful reboot, you can check the clocks in the UI:

CPU Model 	ARMv7 Processor rev 0 (v7l)  -  (Cores: 2)
CPU Frequency 	1200 MHz
CPU Load Average (1, 5, 15 mins) 	0.09,  0.07,  0.05

# cat /proc/cpuinfo

Processor	: ARMv7 Processor rev 0 (v7l)
processor	: 0
BogoMIPS	: 2398.61

processor	: 1
BogoMIPS	: 2398.61

Features	: swp half thumb fastmult edsp 
CPU implementer	: 0x41
CPU architecture: 7
CPU variant	: 0x3
CPU part	: 0xc09
CPU revision	: 0

Hardware	: Northstar Prototype
Revision	: 0000
Serial		: 0000000000000000
4. openssl speed:
# openssl speed aes-256-cbc

Doing aes-256 cbc for 3s on 16 size blocks: 5298660 aes-256 cbc's in 2.98s
Doing aes-256 cbc for 3s on 64 size blocks: 1473282 aes-256 cbc's in 3.01s
Doing aes-256 cbc for 3s on 256 size blocks: 380765 aes-256 cbc's in 3.00s
Doing aes-256 cbc for 3s on 1024 size blocks: 95997 aes-256 cbc's in 3.00s
Doing aes-256 cbc for 3s on 8192 size blocks: 12042 aes-256 cbc's in 3.00s

OpenSSL 1.0.0j 10 May 2012 built on: Sat Aug 24 22:13:38 EDT 2013
options:bn(64,32) rc4(ptr,char) des(idx,cisc,16,long) aes(partial) idea(int) blowfish(ptr) 
compiler: arm-brcm-linux-uclibcgnueabi-gcc -fPIC -DOPENSSL_PIC -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -ffunction

The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes     256 bytes    1024 bytes   8192 bytes
aes-256 cbc      28449.18k    31325.60k    32491.95k    32766.98k    32882.69k
5. Temperature check: go back to
# cat /proc/dmu/temperature
I am seeing 58 degrees (that's with the cooling) BCM4708A is officially rated for 1000 MHz, so ASUS seems to deliberately
underclocking it for AC56U at 800MHz; my guess is that they are keeping full clocks for AC68
nvram set clkfreq=1000,667
nvram commit && reboot
So far I cannot find clear guidance on what are the safe temperatures for the CPU
You just re-affirmed my suspicion - your router is simply overheating (at 80 degrees).
AC56U does not have internal fan, so the only hope convection cooling (right, with those tiny holes) or add-on cooling.

My suggestion: if you can, remove the rear cover (no one sees it in the closet anyway, right?) and you can use standard
80mm case fan just standing few inch away from the router connected to 5-7 volt DC power source (does not have to be USB).
Lower than 12V power will reduce the RPM and noise while still providing sufficient cooling.

Before any overclocking, try to cool off your router to sub-60 and measure performance with VPN on - see if there is any improvement...

6. Memory: used in Asus RT-AC56U - 256 MB (ESMT M15F2G16128A) which is according to M15F2G16128A.pdf
is DDR3 capable of 667/800Mhz! I am going to try 667MHz now. so I applied 1200,667 and... it still works!

The memory in the router is rated for 667 at CL9 or 800 at CL11. Honestly I do not know which one would be more beneficial,
BUT definitely 667 is a lot better than stock 533... and for any real performance difference, we should compare stock memory
speed with maximum - that should yield something.

I would not go anywhere beyond 800 - this is not a PC, and I cannot increase any voltages... Let me try to set 800MHz... and it booted!!!!

7. VPN: So I measure the internet speed using 200Mb file download at and this is highest ever on VPN: 22.5 Mbps
Turning VPN off, the same site: 24.5 Mbps This is, ladies and gentlemen, reason I overclock

Updated 03-09-2013 at 10:07 by Omega (fixed)