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(GUIDE) Getting your Busratio


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Poll: Does Busratio=XX Help? (23 member(s) have cast votes)

Has adding a Busratio to the Boot Plist Helped you?

  1. YES! (13 votes [56.52%])

    Percentage of vote: 56.52%

  2. No. (3 votes [13.04%])

    Percentage of vote: 13.04%

  3. I am not sure. (7 votes [30.43%])

    Percentage of vote: 30.43%

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#1
Zman21295

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(GUIDE) Calculating your Bus Ratio

No more Guessing! Lets get the REAL bus ratio for your CPU!

  • What is Bus Ratio?


In computing, the clock multiplier (or CPU multiplier or bus/core ratio) 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 bold, 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!!!)


Attached File  cpuid.jpg   192.05KB   1483 downloads <- 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:

16.99248120300752 = 17

And if it was (2.40 GHz):

18.04511278195489 = 18

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 "17" and "18".

  • Checking your answer:


We can now check our answer to be 100% sure. It would look like this:

17 x 133 = 2261 or 2.26 GHz

  • You can find Processor Clock Speeds Here:


http://ark.intel.com/Default.aspx

  • 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 17 as our busratio (2.26 GHz Processor), you need to add/change in the Kernel Flags, "Busratio=XX".

<?xml version="1.0" encoding="UTF-8"?>
				 <!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
				 <plist version="1.0">
				 <dict>
					  <key>Kernel</key>
					  <string>mach_kernel</string>
					  <key>Kernel Flags</key>
					  <string>busratio=17</string>
				 <key>Quiet Boot</key>
					  <string>No</string>
					  <key>Timeout</key>
					  <string>5</string>
					  <key>GraphicsEnabler</key>
					  <string>Yes</string>
				 <key>Graphics Mode</key>
				 <string>1920x1080x32</string>
				 </dict>
				 </plist>

  • Please Note:

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....


Attached File  cpuid.jpg   192.05KB   1483 downloads <- 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.




#2
Gringo Vermelho

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Great post, many people seem to throw around completely random busratio= with no base in reality, hopefully this will help.

:D

#3
ludacrisvp

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Is there any need to set the busratio manually on a core 2 duo or is this just needed for the Core i5/i7 quad core based intel chips?

#4
Gringo Vermelho

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No, this is normally not needed on systems with a Core 2 Duo/Quad or a Core Microarchitecture Pentium.

My old Pentium 4 hack running 10.5.8 does not need it either.

#5
Zman21295

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Correct. This is normally only needed on Core i series CPU's.

It helps in Booting in 64 Bit Mode on all cores.

However, in some cases (when not using mach_kernel) this can increase performance on older CPU's such as Core 2 Duo and Core 2 Quad.

#6
rtrtrtrt

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Have a HP Microserver which has an AMD AthlonTM II NEO N36L 1.3. Having trouble getting past the grey apple screen.

Can't tell from the above - would I be recommended to use a bus ratio?

If yes could do with someone confirming pls- is it the 6.5 figure from here?

http://en.wikipedia....s#Athlon_II_Neo

#7
Gringo Vermelho

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No, 6.5 is the clock multiplier, not the busratio.

If you are trying to calculate the Busratio of Older or AMD CPU's, be sure to find the correct external clock.



#8
rtrtrtrt

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ok thanks for the quick reply - but now i'm confused. The OP says

What is Bus Ratio?

In computing, the clock multiplier (or CPU multiplier or bus/core ratio) measures the ratio of an internal CPU clock rate to the externally supplied clock.

doesn't that mean that clock multiplier = cpu multiplier = bus/core ratio = busratio?

late here - will do some more reading tomorrow when i'm not dog tired!

#9
Gringo Vermelho

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Dude..if it was that simple there wouldn't be a guide for it.

multiplier x external clock = CPU clock. Look at the example given:

(Zman21295 @ Dec 22 2010, 12:43 AM)
Most all new Intel CPU’s have an External Clock of 133 MHz

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


Like the guide says, you need to find your external clock (re: the quote in post #7) then divide it by your CPU clock. The resulting number is your busratio.


Sorry, I'm being retarded, YES, your bus ratio is the same as your clock multiplier.

Edited by Gringo Vermelho, 16 December 2011 - 08:04 PM.
inability to read


#10
Zman21295

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Hello and Welcome!

Gringo Vermelho is right, you need to find your correct external clock. I did a little research with little luck, can you confirm that this processor is a 1.3 GHz speed processor?

I believe that your Busratio is (on the dot) 6.5 so rounding to the nearest 1 (Because your clock is so low) you get 7. So try and boot with this command "-v cpus=1 busratio=7"

I am not entirely sure on this answer because there is no solid place for me to get your external or CPU clock. You may to do a bit more digging. :P

#11
Gringo Vermelho

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If his bus ratio is 6.5 and his CPU clock is 1300, then his external clock is 200.

It says here that the real CPU clock is 1339 MHz:
http://www.cpu-world...325LAV23GM.html

That makes his external clock 206...which of course also makes his bus ratio 6.5.

Why do I find it disturbing that his multiplier and his bus ratio are identical. :wacko:

Edited by Gringo Vermelho, 16 December 2011 - 08:05 PM.
And that's the sound of a coin dropping


#12
rtrtrtrt

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processor is 1.3 Ghz - can see it in the BIOS.

Managed to get the HP up and running using the step thro from elsewhere on the site so din't need to use the busratio.

thanks for you help in any case.

#13
Zman21295

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If his bus ratio is 6.5 and his CPU clock is 1300, then his external clock is 200.

It says here that the real CPU clock is 1339 MHz:
http://www.cpu-world...325LAV23GM.html

That makes his external clock 206...which of course also makes his bus ratio 6.5.

Why do I find it disturbing that his multiplier and his bus ratio are identical. style_emoticons/default/wacko.gif


Haha, Yes... I guess that is why we stick to Intel Products. :)

#14
Mr Props

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I have a AMD Phenom™ II X4 945 Processor with 3008.176 MHz and in my BIOS, the Busratio is setted to "Auto" .. should i set it to 15 (15*200=3000) ?

#15
Gringo Vermelho

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Try it and see if it makes any difference, you can always revert it.

#16
nyolc8

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I'm not really understand this... I searched for my cpu external clock and it says it's external clock is "1333mhz (333mhz*4)". 333mhz is my FSB. I don't know what is 4. (CPU multiplier is 8)
So I need to calculate 2660/1333=2? So my busratio is 2? Is this correct? :unsure:

#17
Gringo Vermelho

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I learned this up there in post #11 - bus ratio and CPU clock multiplier is the same thing.

Your FSB is "Quad pumped" - 4*333 = 1333.

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.


However, this doesn't change that your base clock is 333.

The maths are exactly like the first post says - CPU clock divided by FSB equals bus ratio.

2260/333=7.987987987987988 = 8

#18
nyolc8

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Thanks!

#19
marcussebe

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In my PC I have a CPU T8300 2.4 Ghz, but in the processor information work 2.21 Ghz :( why? Can you help me?

THanks

#20
seanz0rzftw

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I have an AMD Phenom II x4 635 at 2.9 Ghz. Where exactly can i find the external clock speed?





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