Re: tigon3: 2466 and bad performance at 32bits/33mhz ?

From: Ben Greear (greearb@candelatech.com)
Date: Tue Aug 06 2002 - 11:47:57 EST


Willy Tarreau wrote:
> On Tue, Aug 06, 2002 at 12:35:08AM -0500, Robert Latham wrote:
>
>>The fast curve is with the 3c996B-T in the 64/66 slot. It peaks out
>>around 850 Mbps. The slow curve is the same card in the 32/33 slot.
>>It peaks around 180 Mbps.
>
> [snip]
>
>>So, am i looking at a hardware limitation? driver quirk? I'm open to
>>any suggestions.
>
>
> on a 32/33 slot, with a quad fast ethernet card, I can reach 400 Mbps
> on good hardware. The *theorical* bandwidth limit is 1.06 Gbps for
> 32 bits/33 Mhz. Of course, there's some overhead, but you would need 80%
> overhead to get you numbers, not very likely...
>
> Perhaps this slot is on another bus, perhaps the latency timer is too
> low and the card receives small chunks at once, or perhaps this bus
> is shared with another hungry device ?
>
> Regards,
> willy

I'm pushing 650Mbps on a 32/33 PCI bus using a Netgear GA620 GigE
card (the card supports 64bit PCI). So, its not exactly a PCI bus
limitation you are hitting unless your PCI chipset somehow really
sucks.

Ben

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-- 
Ben Greear <greearb@candelatech.com>       <Ben_Greear AT excite.com>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear

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