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Re: [SOLVED]Re: Only 8 MB/sec write throughput with NetBSD 5.1 AMD64

On Sun, 9 Oct 2011, Tony Bourke wrote:

On 10/9/2011 3:31 PM, Hisashi T Fujinaka wrote:
On Sun, 9 Oct 2011, Thor Lancelot Simon wrote:
PCIe will handle full duplex 1 gigabit no problem.

The claim is true.

My day job is LAN netwwork performance. One lane of PCIe Gen 1 will
barely handle line rate, but it does handle line rate.

Yeah, PCIe x1 is 2 Gbits, which is just enough for full duplex. Since it's a serial bus (unlike PCI's shared/arbitrated bus) with dedicated bandwidth, you can count on the 2 Gbits at all times too.

The bandwidth is usually measured in Gigatransfers/sec, but remember
PCIe overhead. The maximum data transfer is probably  128 bytes and with
all the memory reads/writes/writebacks and 8b/10b encoding, you'll
likely hit max PCIe bus utilization at line rate.

Hisashi T Fujinaka -
BSEE(6/86) + BSChem(3/95) + BAEnglish(8/95) + MSCS(8/03) + $2.50 = latte

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