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From: krw on 28 Mar 2010 20:22
On Sun, 28 Mar 2010 16:29:21 -0700, Jon Kirwan <jonk(a)infinitefactors.org>
wrote:

>On Sun, 28 Mar 2010 16:06:04 -0700,
>"JosephKK"<quiettechblue(a)yahoo.com> wrote:
>
>><snip>
>>It all starts with Amdahl's Law. Double the speed of one thing and if none
>>of the rest of the system can use the speed increase you get nothing.
>>(slightly overstated)
>
>Sounds like the famous "weakest link" phrase, "A chain is no
>stronger than its weakest link," which apparently traces back
>to the English clergyman Charles Kingley's letter, dated
>December 1, 1856, where he wrote "The devil is very busy, and
>no one knows better than he, that 'nothing is stronger than
>its weakest part.'"
>
>Others have also written similarly, since. See very near the
>bottom of page 433 here, for example:
>http://www.archive.org/stream/workslife10bageuoft#page/432/mode/2up
>
>I guess we can add Amdahl to a long list of many stating the
>exact same thing in slightly different words.

Ahmdahl's Law is more quantitative than that:
http://www.search.com/reference/Amdahl%27s_law


From: Jon Kirwan on 28 Mar 2010 22:04
On Sun, 28 Mar 2010 19:22:10 -0500, "krw(a)att.bizzzzzzzzzzzz"
<krw(a)att.bizzzzzzzzzzzz> wrote:

>On Sun, 28 Mar 2010 16:29:21 -0700, Jon Kirwan <jonk(a)infinitefactors.org>
>wrote:
>
>>On Sun, 28 Mar 2010 16:06:04 -0700,
>>"JosephKK"<quiettechblue(a)yahoo.com> wrote:
>>
>>><snip>
>>>It all starts with Amdahl's Law. Double the speed of one thing and if none
>>>of the rest of the system can use the speed increase you get nothing.
>>>(slightly overstated)
>>
>>Sounds like the famous "weakest link" phrase, "A chain is no
>>stronger than its weakest link," which apparently traces back
>>to the English clergyman Charles Kingley's letter, dated
>>December 1, 1856, where he wrote "The devil is very busy, and
>>no one knows better than he, that 'nothing is stronger than
>>its weakest part.'"
>>
>>Others have also written similarly, since. See very near the
>>bottom of page 433 here, for example:
>>http://www.archive.org/stream/workslife10bageuoft#page/432/mode/2up
>>
>>I guess we can add Amdahl to a long list of many stating the
>>exact same thing in slightly different words.
>
>Ahmdahl's Law is more quantitative than that:
>http://www.search.com/reference/Amdahl%27s_law

Nice!

Jon
From: Anders.Montonen on 29 Mar 2010 06:57
In comp.arch.embedded Nico Coesel <nico(a)puntnl.niks> wrote:
> "TheM" <DontNeedSpam(a)test.com> wrote:
>>Do NPX ARM come with on-chip FLASH?
> Yes, all of them have 128 bit wide flash that allows zero waitstate
> execution at the maximum CPU clock.

The LP17xx series require flash wait states when run at speeds over 20
MHz. When running at full speed four wait states must be inserted (see the
description of the FLASHCFG register, p. 71 in the user manual). The chips
do have a flash accelerator (a tiny, simple cache really) to help hide the
latency.

-a
From: Ulf Samuelsson on 29 Mar 2010 18:55
Anders.Montonen(a)kapsi.spam.stop.fi.invalid skrev:
> In comp.arch.embedded Nico Coesel <nico(a)puntnl.niks> wrote:
>> "TheM" <DontNeedSpam(a)test.com> wrote:
>>> Do NPX ARM come with on-chip FLASH?
>> Yes, all of them have 128 bit wide flash that allows zero waitstate
>> execution at the maximum CPU clock.
>
> The LP17xx series require flash wait states when run at speeds over 20
> MHz. When running at full speed four wait states must be inserted (see the
> description of the FLASHCFG register, p. 71 in the user manual). The chips
> do have a flash accelerator (a tiny, simple cache really) to help hide the
> latency.
>
> -a

I have done some measurements on CM3 using Dhrystone 2.1 & Keil,
and you get the following Dhrystone 2.1 MIPS / MHz.

64 bit 128 bit
0 waitstate 1,223 1,223
1 waitstate 1,068 1,107
2 waitstate 0,915 0,998
3 waitstate 0,774 0,861
4 waitstate 0,660 0,749

based on this,
an LPC17xxx running at 100 Mhz w 4 waitstates
on non-sequential fetch would run around 75 MIPS
or ~61 % of the performance of the zero waitstate
memory.

Adding one waitstate extra latency on non-sequential fetch
removes about 10-15% of the performance from the
otherwise zero waitstate.

BR
Ulf Samuelsson
From: JosephKK on 29 Mar 2010 23:31
On Sun, 28 Mar 2010 19:22:10 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote:

>On Sun, 28 Mar 2010 16:29:21 -0700, Jon Kirwan <jonk(a)infinitefactors.org>
>wrote:
>
>>On Sun, 28 Mar 2010 16:06:04 -0700,
>>"JosephKK"<quiettechblue(a)yahoo.com> wrote:
>>
>>><snip>
>>>It all starts with Amdahl's Law. Double the speed of one thing and if none
>>>of the rest of the system can use the speed increase you get nothing.
>>>(slightly overstated)
>>
>>Sounds like the famous "weakest link" phrase, "A chain is no
>>stronger than its weakest link," which apparently traces back
>>to the English clergyman Charles Kingley's letter, dated
>>December 1, 1856, where he wrote "The devil is very busy, and
>>no one knows better than he, that 'nothing is stronger than
>>its weakest part.'"
>>
>>Others have also written similarly, since. See very near the
>>bottom of page 433 here, for example:
>>http://www.archive.org/stream/workslife10bageuoft#page/432/mode/2up
>>
>>I guess we can add Amdahl to a long list of many stating the
>>exact same thing in slightly different words.
>
>Ahmdahl's Law is more quantitative than that:
>http://www.search.com/reference/Amdahl%27s_law
>
Thanks. If i weren't distracted i might have provided a similar link.
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