NetGear R6400v2 overclocking not working properly

[Radek Strebl]

Using NetGear R6400v2 with 2020.8 K26ARM USB AIO-128K firmware. All nvram clkfreq values over 1000 lead to CPU running at 100MHz only ! Looks like only 800 and 1000 (default) values work, changing RAM speed from default 533 to 800 makes no noticeable difference and I do not know how to test/verify DRAM speed, but CPU speed indicated in the web gui seems to correspond to /proc/cpuinfo BogoMIPS values. With clkfreq=1200,800 or 1400,800 CPU runs at 100MHz only. CPU BCM4708C0 should support up 1400 MHz, I’ve expected at least 1200 like on the older R6400v1 with BCM4708A0 which was working with AdvancedTomato firmware for many years overclocked from default 800MHz.

[M_ars]

Hi

i checked with my RT-N18U

‌

nvram set clkfreq=800,533

nvram commit

reboot → showing correct

‌

nvram set clkfreq=1000,533

nvram commit

reboot → showing correct

‌

nvram set clkfreq=1200,533

nvram commit

reboot → showing correct

‌

What settings for cpu & ram did you test ?

[Radek Strebl]

As I have said I have tried multiple combinations, I was running my older R6400v1 overclocked to 1200/800, so I have tried that too. But everythink with CPU speed over 1000 leads to 100MHz of true speed. I believe that this is some limitation/bug in CFE, but I do not know if CFE is part of the freshtomato firmware update or if it can/must be updated separately, etc. . As I understand it, the value is stored correctly in NVRAM by freshtomato OS, but then it is not applied properly by CFE during boot.

[M_ars]

i checked - From what i can see: newer CFEs like for your R6400v2 use a default clock table (provided by broadcom SDK) and the CFE will restrict cpu & ram according to that table. FreshTomato does not touch the CFE.

→ In the end, the cfe can refuse your desired clock. Other routers like RT-AC68Uv3 should have the same problem, older router versions (like my RT-N18U) not

→ FreshTomato can not change that (You need to modify the CFE to get around the clock limits)

So in my opinion, this topic can be closed

[Radek Strebl]

Thank you for you analysis, and is there anything I could do about it ? For example some tool and manual how to modify CFE ?

[M_ars]

The (netgear) CFE is not open src. At least i do not know a modified CFE for that router. Maybe look at https://www.linksysinfo.org/index.php for help. Some people use AsusWRT on Linksys or Netgear router hardware …

[Radek Strebl]

Thanks, looks like no solution available. Flashing wrong CFE would make it irrecoverable using software solutions and I haven’t seen JTAG solution for Netgear recovery, so I would rather not try.