LPC1788 MIPS?

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LPC1788 MIPS?

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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by Mori_64 on Wed Mar 25 01:06:27 MST 2015
Hello

I can't find the mips of lpc1788 on  neither  data sheet nor user manual ?

any one know about it ?

Thanks
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by starblue on Thu Mar 26 01:38:25 MST 2015

Quote: Mori_64

Quote: starblue

The reference for MIPS is the VAX 11/780, a machine from DEC in the early eighties. So it just means that an ARM Cortex M4 can do about 1.25 times as much computation per clock as that machine.



Actually the reference to clocks is wrong as the VAX ran at 5MHz clock rate.

Rather an ARM Cortex-M4 can do in one clock cycle the amount of computation that corresponds to 1.25 VAX 11/780 instructions. Since the ARM does somewhat less than one instructions per clock (most instructions take one cycle and they aren't executed in parallel), one ARM instruction can do more work than one VAX instruction.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by Mori_64 on Thu Mar 26 00:57:05 MST 2015

Quote: starblue

Quote: Mori_64
125 MIPS at 100 MHz

what does it mean (i know it means million instructions per second) but 1.25  instruction per clock ??!!


The reference for MIPS is the VAX 11/780, a machine from DEC in the early eighties. So it just means that an ARM Cortex M4 can do about 1.25 times as much computation per clock as that machine.



then as i see here   their performance rated against the VAX 11/780 that was marketed as a 1 MIPS machine.

So VAX was 1 Mips and 125Mips= 125*(Vax=1Mps)
it's still 125 Millions of instructions per second !
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by starblue on Wed Mar 25 09:08:22 MST 2015

Quote: Mori_64
125 MIPS at 100 MHz

what does it mean (i know it means million instructions per second) but 1.25  instruction per clock ??!!


The reference for MIPS is the VAX 11/780, a machine from DEC in the early eighties. So it just means that an ARM Cortex M4 can do about 1.25 times as much computation per clock as that machine.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by Mori_64 on Wed Mar 25 08:45:28 MST 2015
Thanks Mike

But the other mcu like ST has this :

"Core: ARM® 32-bit Cortex®-M4 CPU with FPU, Adaptive real-time accelerator (ART Accelerator™) allowing 0-wait state execution from Flash memory, frequency up to 180 MHz, MPU, 225 DMIPS/1.25 DMIPS/MHz (Dhrystone 2.1), and DSP instructions"

and in wikipedia  there is this :

125 MIPS at 100 MHz

what does it mean (i know it means million instructions per second) but 1.25  instruction per clock ??!!
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by MikeSimmonds on Wed Mar 25 04:11:14 MST 2015
It (obviously) depends at what cpu clock speed is set.

Also, although most instruction opcodes take a single cycle, some take more. Memory (and flash) reads/write
can have wait states added. MIPS is pretty meaningless.

But if you are in marketting, just quote the clock speed you are running at. I.e. 72MHz is 72,000,000 (one cycle) instructions per second.

If you are more honest, check the ARM docs to see how may cycles individual instructions take and analyze your code
statisically for a weighted average of instruction count * cycle count. [Not trivial].

Alternative ...

I think I remember a (real world)benchmarks video on the nxp site but I can't remember where after all this time; search for it.

Mike.

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