No more Guessing! Lets get the REAL bus ratio for your CPU!
What is Bus Ratio?
In computing, the
) measures the ratio of an internal CPU clock rate to the externally supplied clock.
A CPU with a 10x multiplier will thus see 10 internal cycles for every external clock cycle.
For example, a system with an external clock of 133 MHz and a 10x clock multiplier will have an internal CPU clock of 1.33 GHz. Because, 10 x 133 = 1330 (1.33).
The external address and data buses of the CPU (often collectively termed front side bus or FSB in PC contexts) also use the external clock as a fundamental timing base; however, they could also employ a (small) multiple of this base frequency (typically two or four) in order to transfer data faster.
Why do you need to set the correct Busratio?: (Will this help or not?)
Ok so basically, the need for the proper busratio is this: It will help OS X to determine what the clock speed of your CPU is. Now, chameleon does this automatically, however does not always do a good job. I recommend injecting this number your self.
What are the downsides? No overclocking! You will most likely not be able to over clock using this, however, this is good because you will not ruin your cpu!
How to Determine Bus Ratio: (You will need a Calculator)
Now that we know what a Bus Ratio is, here is how we calculate it.
Note: Through out this guide, the Busratio Number used in OS X for all of our examples will be
, this will help in keeping track of the Busratio in the Equation.
Most all new Intel CPU’s have an External Clock of 133 MHz (If you are not sure what your External Clock is, you can download a program called CPUID for windows, run it and on the bottom left is a field that says "Bus Speed", this is your External Clock.
BE AWARE:::: CPUID
also has a field that has a multiplier number which is your Bus Ratio, DO NOT user this number in OS X as it is your Current Bus ratio of what ever speed the cpu is currently running, not the designed max!!!)
<- Click it, it will get bigger!
So let’s say you have a Core i5-430m 2.26 GHz (2260) Processor. You will need to change your Clock speed, 2.26 into 2260, just remove the Decimal and add “0”'s to the end to make it a 4 digit number (2.26 > 2260. 2.5 > 2500). So the Mathematical Equation will look like this:
2260 / 133 = 16.99248120300752
Now we are going to round our quotient (answer) number to the nearest ten. Like This:
And if it was (2.40 GHz):
So it’s (Clock Speed, divided by, 133, Equals. Then take our quotient (answer) and round to the nearest ten.)
Note: The rounded quotient (answer) is the number we need in OS X. In our example this number was "
" and "
Checking your answer:
We can now check our answer to be 100% sure. It would look like this:
x 133 = 2261 or 2.26 GHz
You can find Processor Clock Speeds Here:
Deviating from the plan:
You can in some situations, change your clock speed number, for instance, if you have a 2.26 GHz processor yet you only want it to run a max of 2.15 GHz, instead of a 17 bus-ratio number use 16, this will help keep your cpu cool on a full load while also decreasing performance.
BE CAREFUL!!!! YOU CAN FRY YOUR CPU IF YOU OVERCLOCK TO FAR, DO NOT CHANGE YOUR BUSRATIO NUMBER HIGHER THAN THE RECOMMENDED SPEED BY YOUR CPU MANUFACTURER!
Adding to the Boot Plist:
Now that we have our Bus ratio, we are going to add it to our com.apple.boot.plist in the Chameleon /Extra folder. In the case of the example, we are using
as our busratio (2.26 GHz Processor), you need to add/change in the Kernel Flags, "Busratio=XX".
Your external Clock may differ from that used in our example. As of now the only processors that NEED busratio=xx are the Core i Series, all of which have the same, 133 MHz, external clock. If you are trying to calculate the Busratio of Older or AMD CPU's, be sure to find the correct external clock. Like I said before, you can get your external clock from a windows program called CPUID....
<- Click it, it will get bigger!
Also Busratio is the Multiplier between the External Clock and Core clock. The Busratio=xx flag, in OS X, is only required with Multi-Core, Core i Series processors that not booting correctly.
You can, however, use the busratio=xx flag on older CPU's such as Core 2 Duo/Quad for increased performance, although this is normally not needed.