usa2k
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NJRob
join:2002-05-20
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| »www.clifton.nl/bogomips.html
Great - how about a real benchmark...
3. The frequently asked questions about BogoMips
Several authors have contributed to my knowledge of BogoMips. In this place, I would like to thank them highly.
3.1. What are BogoMips
Quoted from the Internet, origin unknown but brought to the attention by Eric S Raymond esr@thyrsus.com, and Geoff Mackenzie freon@dialstart.net, there is an humourously illustrative definition of BogoMips as ''the number of million times per second a processor can do absolutely nothing.''
On a more precise basis, from Lars Wirzenius' wirzeniu@kruuna.Helsinki.FI mail of 9 September 1993, explaining Bogomips, with additional detailed information by Alessandro Rubini, rubini@morgana.systemy.it, and by howto-author Wim van Dorst:
`MIPS is short for Millions of Instructions Per Second. It is a measure for the computation speed of a program. Like most such measures, it is more often abused than used properly (it is very difficult to justly compare MIPS for different kinds of computers).
BogoMips are Linus's invention. The kernel (or was it a device driver?) needs a timing loop (the time is too short and/or needs to be too exact for a non-busy-loop method of waiting), which must be calibrated to the processor speed of the machine. Hence, the kernel measures at boot time how fast a certain kind of busy loop runs on a computer. "Bogo" comes from "bogus", i.e, something which is a fake. Hence, the BogoMips value gives some indication of the processor speed, but it is way too unscientific to be called anything but BogoMips.
The reasons (there are two) it is printed during boot-up is that a) it is slightly useful for debugging and for checking that the computers caches and turbo button work, and b) Linus loves to chuckle when he sees confused people on the news.'
BogoMips are being determined in /usr/src/linux/init/main.c (simple C algorithm, with a nice example of floating point arithmetic within the fully integer kernel), and the pertaining kernel variable loops_per_sec is used in several drivers for more serious purpose. The actual delay function udelay() is in assembler, and therefore each port has its own definition in /include/asm/delay.h. The loops_per_sec variable and the udelay() function are used in numerous drivers, see:
cd /usr/src/linux #or where else source is located
find . -name '*.[hcS]' -exec fgrep loops_per_sec {} /dev/null \;
find . -name '*.[hcS]' -exec fgrep udelay {} /dev/null \;
The BogoMips calculation loop for the non Intel CPUs is similar but not the same, because it is programmed in another assembler language. BogoMips is however the only portable way over the various CPUs (Intel-type and non Intel-type) for getting an indication of the CPU speed. Even CPU clock speed is not available on all CPUs. |
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usa2k
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| said by NJRob  : ... BogoMips is however the only portable way over the various CPUs (Intel-type and non Intel-type) for getting an indication of the CPU speed. ... If I take this part by itself, . . . is it out of context?
My AMD64 2800+ is getting 3563.52 bogomips now I have the clock right.
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TwoFrogs
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join:2002-01-20
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| reply to usa2k
foldy4serverprocessor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 8
model name : AMD Athlon(tm) XP 1800+
stepping : 0
cpu MHz : 1540.051
cache size : 256 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow
bogomips : 3073.63 blade 1processor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 8
model name : AMD Athlon(tm) XP 1900+
stepping : 0
cpu MHz : 1571.442
cache size : 256 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow
bogomips : 3132.62 --
"Scapegoat: The Secret to Success is Knowing Whom to Blame" -- Despair, Inc.
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PinHead
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join:2002-06-19
The Dungeon
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Been a while since I had to do anything with NOOPS, but it was simply an instruction that did nothing for 1 clock cycle.
Seems like a simple instruction on an Intel P3 takes 4 clock cycles. 1+1 similar to 4 NOOPS. And 8 clock cycles on a P4. 1+1 = 8 NOOPS.
Now the reason the Intel Math Coprocessor runs twice the speed of the core is because the instructs take twice the clock ticks. Which really means it runs at normal speed on a complex math calculation.
Bet you won't hear that in their advertisements!
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time nor tide wait for no man... |
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