Overclocking on Asuswrt-Merlin 378.56_2 (RT-AC68U and RT-N66U)

joegreat

Very Senior Member

• Nov 6, 2015

• #1

First of all the simple observation from the RT-N66U device:
After update of the firmware the overclocking need to be set once via nvram set clkfreq=662,331,165 and nvram commit - and it will survive the restart (hard and soft - see below).
Otherwise the default values of clkfreq=600,300,150 are used.

Now the more complex (and important) behavior on the RT-AC68U device after the update to the version 378.56_2:
I have set the desired overclocking in the init-start script via nvram set clkfreq=1200,666 and nvram commit to overcome the lock-down of the current Asus firmware.

After a hard reset (power toggle) the settings force the CPU to the overclocking performance:

Code:

chief@RT-AC68U:/tmp/home/root# cat /proc/cpuinfo
Processor  : ARMv7 Processor rev 0 (v7l)
processor  : 0
BogoMIPS  : 2398.61
processor  : 1
BogoMIPS  : 2398.61

And the nvram show | grep clk shows: clkfreq=1200,666 - same as the web interface (reading the same value).

But after a soft reset (reboot button in web GUI for reboot command via telnet) the CPU performance is at default speed settings only:

Code:

chief@RT-AC68U:/tmp/home/root# cat /proc/cpuinfo
Processor  : ARMv7 Processor rev 0 (v7l)
processor  : 0
BogoMIPS  : 1599.07
processor  : 1
BogoMIPS  : 1599.07

But still the nvram show | grep clk shows: clkfreq=1200,666 - which is not the true speed!

Conclusion: if you want your router to run faster, do not forget to set the init-start values and always do a power toggle in case you need to restart it!

Update:
Over night the NVRAM variable was reset to clkfreq=800,666 - looks like something is re-reading the CFE values and updating the NVRAM settings...
But the good news is that BogoMIPS : 2398.61 shows that it's still overclocked.

With kind regards
Joe

 

Last edited: Nov 7, 2015

K

kvic

Part of the Furniture

• Nov 7, 2015

• #2

Ouch! Our previous conclusion that clkfreq is only overridden on startup is not valid then...

Could you try adding the same nvram statements also into /jffs/scripts/services-stop?

That's the same nvram statements in both /jffs/scripts/init-start and /jffs/scripts/services-stop.

 

RMerlin

Asuswrt-Merlin dev

• Nov 7, 2015

• #3

init-start might be too early, it's possible that the nvram gets overwritten only later on during the boot process. services-start might be a safer location.

 

joegreat

Very Senior Member

• Nov 7, 2015

• #4

RMerlin said:

init-start might be too early, it's possible that the nvram gets overwritten only later on during the boot process. services-start might be a safer location.

Click to expand...

Hi,

Adding the NVRAM settings to service-start does not change the behavior: Only cold start (power toggle) makes overclocking work.

On top: Something is changing the NVRAM clock settings after reboot: Over night it get reset to default. Is there a kind of watchdog who enforces the Bootloader (CFE) settings while the router is running?

With kind regards
Joe

 

joegreat

Very Senior Member

• Nov 7, 2015

• #5

kvic said:

Ouch! Our previous conclusion that clkfreq is only overridden on startup is not valid then...

Could you try adding the same nvram statements also into /jffs/scripts/services-stop?

Click to expand...

Hi,

Interesting: adding the NVRAM clock settings to the service-stop script does the trick:
Now the router is also overclocked when doing a soft boot. But why is this working now?
The init-start is running anyway after boot and set's the overclock values...

And: What makes the difference for overclocking between a hard reset and the soft one?

With kind regards
Joe

 

Last edited: Nov 7, 2015

amorak

Regular Contributor

• Nov 8, 2015

• #6

I have an RT-N66U and putty'ed in and set:

nvram set clkfreq=662,331,165
nvram commit

but after a while, on the sysinfo page (http://192.168.1.1/Tools_Sysinfo.asp) it resets the displayed speed to 600MHz... Is the router periodically resetting it's speed or?

 

joegreat

Very Senior Member

• Nov 9, 2015

• #7

amorak said:

...but after a while, on the sysinfo page (http://192.168.1.1/Tools_Sysinfo.asp) it resets the displayed speed to 600MHz... Is the router periodically resetting it's speed or?

Click to expand...

Check Bogo-MIPS for the speed - the NVRAM setting is reset.

 

R

ryzhov_al

Very Senior Member

• Nov 9, 2015

• #8

joegreat said:

looks like something is re-reading the CFE values and updating the NVRAM settings...

Click to expand...

Available pairs of CPU/RAM frequencies for RT-N66U is...

Code:

$ cat ./asuswrt/release/src-rt/shared/hndmips.c
...
/* cpu, ddr, axi, proc_PLL, */

{ 200,100,50 0xc0011080, },
{ 300,150,75 0xc00110c0, },
{ 400,200,100 0xc0011100, },
{ 500,250,125 0xc0011140, },
{ 600,300,150 0xc0011180, }, default
{ 632,316,158 0xc00157e8, },
{ 650,325,162 0xc00111a0, },
{ 662,331,165 0xc00111a8, },

 

R

ryzhov_al

Very Senior Member

• Nov 9, 2015

• #9

amorak said:

but after a while, on the sysinfo page (http://192.168.1.1/Tools_Sysinfo.asp) it resets the displayed speed to 600MHz... Is the router periodically resetting it's speed or?

Click to expand...

Too old CFE?

 

joegreat

Very Senior Member

• Nov 9, 2015

• #10

ryzhov_al said:

Too old CFE?

Click to expand...

The NVRAM reset happens also on the latest Bootloader (CFE) 1.0.1.9 - but the Bogo MIPS show that it stays overclocked.

 

R

ryzhov_al

Very Senior Member

• Nov 9, 2015

• #11

May be it's an overclocking glitch then. Anyway, better to lower CPU/RAM frequencies to avoid it.

 

ASAT

Senior Member

• Nov 12, 2015

• #12

Is it wrong to edit the CFE 1.0.2.1 of my RT-AC68U with the Vortex CFE Editor and then flash the updated CFE back to the router?

Example:
Change "clkfreq=800,666" to "clkfreq=1200,800" in the CFE?

Seems like this would persist the clkfreq setting. Will it brick the router? I am not brave enough to try it.

Currently, I'm on 378.55 with clkfreq=1400,800, cpu temp is 57C.

nvram get model
RT-AC68U

nvram get clkfreq
1400,800

nvram get bl_version
1.0.2.1

cat /proc/cpuinfo
Processor : ARMv7 Processor rev 0 (v7l)
processor : 0
BogoMIPS : 2798.38

processor : 1
BogoMIPS : 2798.38

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

 

Last edited: Nov 12, 2015

RMerlin

Asuswrt-Merlin dev

• Nov 12, 2015

• #13

Overclocking at the CFE level is a really bad idea. If your router becomes unstable with the new clock settings as it ages, you will have no way of recovering your router.

 

ASAT

Senior Member

• Nov 12, 2015

• #14

RMerlin said:

If your router becomes unstable with the new clock settings as it ages, you will have no way of recovering your router.

Click to expand...

Anyone successfully re-flash the CFE via the JTAG port? I think we'd just need to know the JTAG pinouts, and the location of the CFE in flash memory?
http://wiki.openwrt.org/toh/asus/rt-ac68u

 

RMerlin

Asuswrt-Merlin dev

• Nov 12, 2015

• #15

ASAT said:

Anyone successfully re-flash the CFE via the JTAG port? I think we'd just need to know the JTAG pinouts, and the location of the CFE in flash memory?
http://wiki.openwrt.org/toh/asus/rt-ac68u

Click to expand...

I don't remember if the bcm4708 is supported yet. Ask @hggomes , he's done some JTAG tinkering.

 

F

fearz

Senior Member

• Nov 12, 2015

• #16

Hi,

Is it safe overclocking the 66u? what are the risks? worst case scenarios?

Also is there any really noticeable increase in performance?

Lastly, would it differ if its overclocked to 630 from 666? is there any noticeable difference? / What is the max overclock one could go with that router?

 

J

jsmiddleton4

Very Senior Member

• Nov 12, 2015

• #17

"Change "clkfreq=800,666" to "clkfreq=1200,800" in the CFE?"

The 68U I just bought is at 1000 already. Having played around with OC the performance increase going for 1000 to 1200 was not that great. Fun? Sure. Real world improvement? I saw none.

 

J

jsmiddleton4

Very Senior Member

• Nov 12, 2015

• #18

All the steps to d/l, edit, upload and then install a new CFE is in the threads regarding converting a TMOBILE tweaked router back into an ASUS router. No JTAG required.

 

ASAT

Senior Member

• Nov 12, 2015

• #19

jsmiddleton4 said:

No JTAG required?

Click to expand...

Sure, you can set "clkfreq=1400,800" in the CFE and then use mtd-write to flash it. However, if this change causes instability and prevents the router from booting, then a JTAG recovery is the only option.

Currently, I am not aware of any "officially endorsed" JTAG recovery method for the RT-AC68U. When you mess with the factory defaults of the router, you can permanently brick it.

 

mstombs

Very Senior Member

• Nov 13, 2015

• #20

The JTAG thread is here (still not sure about AC68):-

http://www.snbforums.com/threads/how-to-asus-routers-jtag-recovery.19077/

But you really need to get this working before you have a problem!

I expect clkfreq only takes effect in CFE boot, for example in the source for some device CFE

https://github.com/RMerl/asuswrt-me...arm/board/bcm947xx/src/bcm947xx_machdep.c#L52

If overclocking note that some memory timings are stored in the nvram header, not plain nvram vars, mucking with these seems dangerous

https://github.com/RMerl/asuswrt-me...ab2/release/src-rt-6.x/include/bcmnvram.h#L29