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Clock frequencies for WRT54G v4 discovered - are different

Discussion in 'Cisco/Linksys Wireless Routers' started by dbcch, May 31, 2006.

  1. dbcch

    dbcch LI Guru Member

    Some of you may have noticed that trying to overclock a WRT54G v4 or v5 to 252mhz or above will result in the processor really running at its default speed of 200mhz.

    DD-WRT and some other firmwares will show in the web UI that the processor is running at whatever speed you tried to overclock at because it is pulling the speed from the nvram variables. Many users mistakenly believe they are running at 252mhz or above when they are not.

    To determine the true speed of your processor, use 'cat /proc/cpuinfo' or 'dmesg'.

    I did some digging and discovered that the WRT54G v4.0 and v5.0 hasve a BCM3302 r0.8 instead of BCM3302 r0.7 found in previous models. This CPU uses a different frequency table in the sbmips.c than do previous versions of the WRT54G and GS.

    The CPU and SB clock ratio is fixed to 2:1, so the SB clock value (second part of clkfreq) is always ignored for these versions.

    For the WRT54Gv4 and WRT54Gv5, the highest valid clock frequency of the CPU is 250mhz, which means 125mhz for the SB clock.

    Therefore, to set the highest possible clock frequency on your WRT54G v4 or WRT54G v5:

    WARNING: DO NOT TRY TO SET PREVIOUS VERSIONS TO 250MHZ AS IT MAY BRICK YOUR ROUTER! THIS IS FOR VERSION 4 AND 5 ONLY!

    Code:
    nvram set clkfreq=250
    nvram commit
    reboot
    
    The CFEs (v3.6 instead of v3.4) also contain some protection against bad clock frequencies, making them more difficult to brick by overclocking. For instance, if you give an invalid frequency below the maximum of 250, it will find the next closest match. And as already described, if you give an invalid frequency above 250mhz, it'll simply default to 200mhz.

    I have a heatsink (though not a great one) and an internal fan on my WRT54G v4, but it's been running 250mhz stable for quite some time. I've been running my WRT54G v5 at 240mhz stable with only a heatsink for a few weeks. I believe either will run ok at 250mhz without any additional cooling, but they will run quite hot and therefore should not also be using an aggressive TX power setting than the default, for this will generate even more heat.

    I posted all this new information on the OpenWRT WRT54G Wiki.
     
  2. Toxic

    Toxic Administrator Staff Member

    since you wish to overclock your WRT54G, can you give us some performance gains in doing such a thing?

    there are benchmark databases for CPUs that are overclocked so perhaps you'd like to set a standard in benchmarking the standard and overclocked differences in overclocking.

    note: overlcocking your router can in some circumstance, render your router inoperable.
     
  3. 22bsti

    22bsti LI Guru Member

    maybe i missed this but how do you oc a WRT54G v5 i thought it ran vxworks and therefore alt fw wont run on it(well without a jtag and some work) ??
     

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