From: kelly@cliffhanger.com
Date: Sun Jun 10 2007 - 11:09:59 ART
Noel,
Thank you for your simplified and clear
explanation. I've not seen such an explanation up
to this point.
It's very helpful to those of us without this depth
of knowlegde in these areas.
--
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Impossible Triangle
M. C. Escher
Big riffs, massive grooves, and expansive improvisations
Quoting Noel Bourke <cros13@gmail.com>:
Core 2, no question. I'm simplifying a bit here
with my explanation of why, and glossing over
quite a few issues.
Core 2 is a "four wide" architecture, meaning that
it can issue four instructions per clock cycle.
All of AMD's products are "3 wide". Predictability
of instructions is crucial here to gain maximum
benefit.
Also due to the that emulation generates quite
predictable instructions, dynamips benefits from a
longer pipeline. This gives the core 2's 14-stage
an advantage over the AMD 12-stage. Its also the
reason why the 31-stage p4 (netburst) did so well
with binary patching (e.g. VMware) and
architecture emulation (e.g. PearPC).
The Core2's dynamically allocated shared cache
also helps. More cache can be used by a core
running a dynamips process which is under greater
load (e.g. emulating say a hub router, or a router
running more protocols than the others). AMD has
the hypertransport bus and onboard memory
controller which is not as decisive an advantage
as the core 2 cache.
A dynamips can also be aware of data loaded to the
cache by a process running on the other core which
with a static image file like the ios image You
are using with dynamips can reduce the amount of
times the process has to access the drastically
slower main memory.
So to simplify a bit further, say your dynamips
process on one core is running though the section
of the ios image to send an ospf hello. 1.3
seconds later another dynamips process running on
the other core has to send a hello too, your AMD
has to take a comparatively long commute to the
memory controller (yes even though the memory
controller is onboard its still further then the
cache), and then an epic transcontinental journey
to main memory. For all it cares your other cpu
cores cache could be in siberia instead of right
beside it on the die, its not even aware of its
existence let alone contents. The AMD will
probably have half or less cache then the core 2
regardless.
OK enough on the CPU. Core 2 it is then.
RAM....uhuh....ok....go for the fastest you can
get (PC5200+). no manufacturer or retailer i know
of tells you any more specifics, such as timings
so ignore the rest.
As to amount of RAM....errr i'm going to say this
later but any 32 bit OS is limited to 4GB of
memory (excluding PAE but that isent relevant as 4
GB 'aint the major barrier. On windows memory is
handled pretty awfully. what happen when you have4
gigs of memory is say for example on 32bit XP,
each process is essentially limited to 1.8 gb.
Last point, don't run dynamips on windows. Its
running not quite natively on an architecture
which bears little resemblence to the robust unix
box it was designed for, which happens to have
awful memory management, a bolted on network
stack, pitiful management of multiple processors
and multithreading that grinds to a halt when
under load. thats not microsoft-bashing, windows
is severely structurally flawed due to the bolting
on of not just features but entire concepts (like
multi-user and networking), both apply to
dynamips.
Linux will run daynamips with the same configs
10-20% faster on any processor. and it won't
become unusable at 100% cpu usage because
processes are pretty much forced to play nice.
If you are voluntarily using dynamips on vista i'd
call the nice doctors in the white coats or you
could get a job far enough away from computers
that you cant hurt them anymore.
Do
- use any 64bit distro of linux,
- do download the source code from the dynamips site,
- do compile using
gcc 3.2+ using cpu specific optimisation
and the -O3 option for threading,
- do set your idle-pc correctly.
I emulate up to 24 7200s simultaneously here on my
laptop (2.33Ghz Core 2, 4GB Ram).
Apologies for the quasi-religous ferver.
Regards,
Noel Bourke
On 6/9/07, Con Spathas <con@spathas.net> wrote:
>
> Check out http://7200emu.hacki.at/
>
> This question has been asked many times there!
>
> Cheers...
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> lalit gupta
> Sent: Saturday, 9 June 2007 08:19
> To: Cisco certification
> Subject: Maximum number of instances on dynamips/dynagen.u
> I am planning to buy a laptop for running maximum number of instances on
> dynamips/dynagen.
>
> Which configuration will you geniuses recommend.
>
> 1) AMD 64-bit process 2GHz
> 2 GB RAM
> or
> 2) Core 2 Duo processor 2 GHz
> 2 GB RAM
>
> Also will it help if I increase the RAM further more.
>
> Please if you can given any more information which will be useful please
> don't hesitate to reply.....
>
> Regards
> lalit
>
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