Date: Thu, 10 Jul 1997 23:17:29 -0700 From: David Greenman <dg@root.com> To: dennis <dennis@etinc.com> Cc: rcramer@sytex.net, isp@FreeBSD.ORG Subject: Re: T1/T3 Upgrade Options? Message-ID: <199707110617.XAA05228@implode.root.com> In-Reply-To: Your message of "Thu, 10 Jul 1997 17:57:33 EDT." <3.0.32.19970710175730.00b07380@etinc.com>
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>A major factor to consider is that its very difficult to do 86Mbs (T3 is >full duplex) >with an addon card on the PCI bus because the sustained throughput rate >is often pretty low. Other bus masters (ethernets, for example) will futhur >reduce the burst capability. While PCI bursts to 128MB/s, very few PC >products have sustained throughput rates over 100Mb/s. If you have a >100Mbs ethernet card on the same bus (you'd have to) the number is >cut in half. plus bus masters can't be controlled so you have contention >issues. You're mixing bits and bytes, Dennis. The PCI bus is capable of 132 MBytes/sec which is 1.056 Gbits/secs. There are no problems at all with the PCI bus being fast enough to handle 2 fast ethernet cards and a few full duplex T3 interfaces. In fact most memory subsystems wouldn't be limiting factor, either. There are problems with having enough CPU power to queue small packets at full rate, however. Just one fast ethernet is capable of about 140,000 packets per second, and you can't even get a third of that rate with a PPro/200. So unless your average packet sizes are large, you won't be able to keep the wire saturated. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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