Overclocking RT-AC56U

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Sky1111

Senior Member
DISCLAIMER: if you are willing to experiment with overclocking, you assume full responsibility for your actions. You are risking to fry it, and unlike a PC, you cannot easily remove the battery and clear the CMOS to reset the setting should the router refuse to boot.
Luckily there is a recover procedure which helped me - the instructions will be provided below
REMEMBER: Overclocking may result in reduced stability AND PREMATURE DEATH of your router, especially if you are not providing sufficient cooling!

Please do check your CPU temperatures before attempting to overclock - if with the stock clocks you are at 70 degrees or more, DO NOT overclock - it may accelerate your router death!

Please change one clock at a time - default memory, find a safe limit for your CPU by increasing the clocks in increments, and once you determined CPU limit, clock it back to default value and repeat the same with memory. Pushing both at the same time may result in $200 brick


ADDITIONAL DISCLAIMER: I am not claiming I know all the answers. I am hoping that the community will contribute to this thread

REASONS WHY YOU MIGHT BE INTERESTED IN OVERCLOCKING YOUR ROUTER:
- improved performance while running OpenVPN client on the router itself
- improved performance if you found a way to overload the router's CPU
- just for fun of it :)

PREREQUISITES
- Latest Merlin FW for your router
- additional cooling to keep the system stable under the load. It is a must if you care for your router. AC56 has a big heatsink visible thru the holes of the read panel, you can use an external USB fan to directly blow air on the rear panel of the router. I am planning to install a small high grade quiet fan directly on the rear cover; once I get to actually implement that I will share pics and instructions (and yes, many of you can probably do a much better job :)
 
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Sky1111

Senior Member
HOW TO RECOVER IF YOUR ROUTER HANGS AFTER APPLYING NEW CLOCKS:

Option 1 - using WPS button
- power off the router
- press and hold WPS button on a side of the router
- power the router up (while NOT releasing WPS button)
- after ~10 seconds release the WPS button
- if you are lucky, this will clear NVRAM and you will be able to access 192.168.1.1 to re-configure the router

Option 2 - using reset button
- power down the router
- press and hold the reset button
- power up while still pressing the reset button
- wait until front power LED starts slowly blinking, release the reset button

Now the router is in recovery mode.

On hardwired PC change NIC Settings to static IP address 192.168.1.10, default subnet 255.255.255.0

In your browser go again to 192.168.1.1

You should see recovery console, with options to clear NVRaM and flash FW firmware

Clearing NVRAM will reset your router. Hence I suggest to save your router configuration before attempting to overclock - greatly speeds up the recovery
 
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Sky1111

Senior Member
HOW TO OVERCLOCK RT-AC56U

1. Navigate to http://192.168.1.1/Tools_RunCmd.asp

2. in the cmd window, copy paste/enter:
nvram set clkfreq=1200,800 - this will set CPU clock to 1200MHz and memory to 800 (for comparison - the stock is 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:
http://192.168.1.1/Tools_Sysinfo.asp

CPU
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
 
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Sky1111

Senior Member
Temperature check:

go back to http://192.168.1.1/Tools_RunCmd.asp

run: 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

So far I cannot find clear guidance on what are the safe temperatures for the CPU...
 

Sky1111

Senior Member
Next steps:

- figure out the CPU load per core (to check if VPN client is actually loading both cores or not)

- figure out the memory clocks and try to tweak them (often overlooked, but memory bandwidth is helping to improve performance)

- finally install the fan on the router itself :)
 

oversim

Regular Contributor
Great :) In N66U in nvram we have:
Code:
clkfreq=600,300,150

The first value are the Mhz of cpu core, but I don't know about 300 and 150 values.
Reduced speed value? Memory clock?

Now I'm trying 630,300,150...
 

primitivo

Senior Member
Finally! Thanks for the guide.

Questions:

1. Is there any reason why Asus deliberately underclocked the CPU to 800Mhz?
2. Would it be safe to assume that overclocking it to 1000Mhz should not require additional cooling?
3. Which temperatures were you getting before OC? Mine is running at 80 degrees all the time (even when there is not much traffic passing through), so the question remains what are the safe numbers to not fry the CPU.
 

Sky1111

Senior Member
The reasons why ASUS underclocked AC56 can be twofold (and this is just a guess):

- product positioning - AC68 is the king of the hill and our AC56 is meant to be a cheaper product (even though it is quite pricey!)

- thermals. lower clocks = lower TDP = less problems cooling it


If you are running at 80 degrees Celsius, I would be worried for thermal throttling - not sure if this specific CPU supports it, but it is definitely too high. I turned off the fan and I am checking how far my temps will go

Does your router placed in away from sources of heat and have enough natural airflow?
 

Sky1111

Senior Member
with the fan off, the temperature quickly went from 58 degrees to 65 in a matter of few minutes...
 

primitivo

Senior Member
[...]
Does your router placed in away from sources of heat and have enough natural airflow?

My router is placed in a storage box where all fibre / wires and electrical switches are placed. There is not much natural airflow I would say and because it is placed outside of of entrance doors, the temperature there is approx. 30celsius. I will see if adding USB cooling fan will help.

with the fan off, the temperature quickly went from 58 degrees to 65 in a matter of few minutes...

How can I check whether fans are working properly or not?

Edit: you probably meant the external fan off. How to check if the internal cooling works properly then :)
 

Sky1111

Senior Member
My router is placed in a storage box where all fibre / wires and electrical switches are placed. There is not much natural airflow I would say and because it is placed outside of of entrance doors, the temperature there is approx. 30celsius. I will see if adding USB cooling fan will help.



How can I check whether fans are working properly or not?

Edit: you probably meant the external fan off. How to check if the internal cooling works properly then :)

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...
 

Sky1111

Senior Member
Great :) In N66U in nvram we have:
Code:
clkfreq=600,300,150

The first value are the Mhz of cpu core, but I don't know about 300 and 150 values.
Reduced speed value? Memory clock?

Now I'm trying 630,300,150...

How do I get the current values - Merlin?
For example, what are the memory clocks for AC56U? I only know the CPU default clocks - 800MHz...
 

primitivo

Senior Member
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...

I think I prefer USB cooling solution for the time being.
It is also hard to say if it is overheating or not, since it works very stable and there are no official guidelines at what temps it should run.

What is a little bit strange is that CPU temp stay at 80-81 all the time (I have never seen other than these two values), regardless if there is any activity or if there is VPN running at max speeds with one of the CPU hitting close to 100% load. It works stable at all times though.

If you want to check CPU load per core do the following:
1. ssh [email protected]
2. enter password
3. type: top
4. press 1

VPN doesn't use multi-cores unfortunately which I thought it will and that's why I was disappointed at first with lower than expected VPN speeds.
 

RMerlin

Asuswrt-Merlin dev
The correct default values for the RT-AC56U is:

Code:
clkfreq=800,533

First number is CPU, second number is RAM.

I think the CFE version used in retail products wasn't properly filling these default values (I use a newer CFE on mine).
 

RMerlin

Asuswrt-Merlin dev
What is a little bit strange is that CPU temp stay at 80-81 all the time (I have never seen other than these two values), regardless if there is any activity or if there is VPN running at max speeds with one of the CPU hitting close to 100% load. It works stable at all times though.

AFAIK, there is no dynamic clock functionality in the firmware. No idea if it would be technically possible to implement, chances are it would not be such a good idea for latency reasons.

If you guys want to know the nominal temperature for this chip, you will have to pay a few thousand $$$ for the Broadcom SDK. (and before you ask, I don't have access to that information either :) )
 

Sky1111

Senior Member
so I applied 1200,667 and... it still works!

Merlin, is there any way to check what the clocks are? the sysinfo page only shows CPU clock, but not memory clock... in other words, I have no idea what the memory is running now...
 

RMerlin

Asuswrt-Merlin dev
so I applied 1200,667 and... it still works!

Merlin, is there any way to check what the clocks are? the sysinfo page only shows CPU clock, but not memory clock... in other words, I have no idea what the memory is running now...

Not that I know, no. This is a proprietary SoC (Broadcom), no idea how to access its registers to see how it's configured.

Keep in mind that the clock is just part of the equation. Asus might be running it at a slower clock, but using tighter timings, which means there's no guarantee it will run stable with an increased clock rate. Timings might need to be increased too.

This is similar to your typical DDR3 1333 RAM running at CL10, but it will also run at 1600 with CL11.
 

Sky1111

Senior Member
Not that I know, no. This is a proprietary SoC (Broadcom), no idea how to access its registers to see how it's configured.

Keep in mind that the clock is just part of the equation. Asus might be running it at a slower clock, but using tighter timings, which means there's no guarantee it will run stable with an increased clock rate. Timings might need to be increased too.

This is similar to your typical DDR3 1333 RAM running at CL10, but it will also run at 1600 with CL11.

absolutely correct. 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...
 

Sky1111

Senior Member
... and it booted!!!!

So I measure the internet speed using 200Mb file download at testmy.net 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 :cool:
 

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