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RE: [avr-gcc-list] Trouble with division

From: Dean Ferreyra
Subject: RE: [avr-gcc-list] Trouble with division
Date: Sun, 15 Jun 2003 08:47:57 -0700


Larry has it right when he writes "relative times".

You can look at a version of the old source for my program here


to give you an idea of where these number came from.  For example, the test
for addition looks like this

  volatile uint8_t x_u8 = 67;
  volatile uint8_t y_u8 = 3;
  volatile uint8_t z_u8 = 0;
  TEST("x+y", z_u8 = x_u8 + y_u8);

where TEST is a macro that runs the second argument in a tight loop.  So the
"Cycles" number you see includes reading the bytes out of memory, adding
them, and assigning the result back into memory.


-----Original Message-----
From: address@hidden
[mailto:address@hidden Behalf Of Ulrich Schweitzer
Sent: Sunday, June 15, 2003 7:50 AM
To: avr-gcc List
Subject: Re: [avr-gcc-list] Trouble with division

On Sunday 15 June 2003 15:42, Larry Barello wrote:
> Here is an old email with relative times for various math operations in
> avr-gcc.

Thanks a lot, the list is very helpful.
I'm a bit confused though. Doesn't Atmel brag about "Up to x MIPS
throughput at x MHz" for all of their AVRs? How can this be when a simple
add operation takes 7 cycles?

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