DragonFly BSD
DragonFly users List (threaded) for 2005-03
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Re: Differences between AMD and Intel CPUs [was: Re: Dragonfly andHyperthreading....]

From: "Thomas Edward Spanjaard" <t.e.spanjaard@xxxxxxxxxxxxxxxxxx>
Date: Thu, 10 Mar 2005 15:52:12 +0100

<EM1897@xxxxxxx> wrote in message news:02FB1A9B.3D7CFFE9.000424FF@xxxxxxxxxx
I'd much rather hear why you don't think that the bus
speed of the network adapter is a worthy criteria for
hardware selection than your opinion on my conduct.
Your reasoning is what gives you credibility; not your
name. It seems implausible that you don't understand
what a bottleneck a standard PCI bus is.

Just as a sidenote, I've been able to get 12.3MiBps each out of two standard 3c905ctx-m over a single PCI bus, with concurrent disk access (the controller where network data was flowing to was also on the same bus, old peecee). It just pays to investigate the options the hardware has for you, and busmastering PCI with DMA certainly ups the average attained speed on the 'slow' PCI bus. Of course, for Gigabit you are limited even by the theoretical maximum transfer rate, but there's PCI-X out there, as you mentioned, to alleviate that. When it comes to PCI-X, *all* boards are relatively expensive, not just the AMD-powered ones. For instance, take a look at the Tyan catalogue, it gives you a fairly good impression of server mainboard price differences accross the three (four including the Athlon MP) x86 server platforms.

Knowing that, it sounds ridiculous to claim that you can get a 3.2GHz P4 with a motherboard with PCI-X for under 300$. Unless it's a special deal ofcourse, but special deals are not to be relied on when making proper cost estimates.

On the point of MP performance, everyone knows that only multithreaded applications can really take advantage of it, and network stacks aren't usually MP compatible. Knowing that high traffic means lots of interrupts, it's also easy to see why an MP machine with non-MP-compatible network stack performs worse than a UP machine.

Of course, to the 'dumb' manager who needs to get a set amount of performance, this all doesn't matter as long as he gets it for a reasonable price. Maybe it's here where we're shifting: the bulk of the list users tend to go for the best solution, whereas said manager goes for the solution that solves his problems the quickest at the lowest cost.

Now as a personal note to 'EM1897', please fix your client to properly support message threads :).

-- Thomas E. Spanjaard

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