Difference between 32 and 64-bit gigabit ethernet cards?

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Postposted on Mon Feb 18, 2002 12:17 pm

We're going to be upgrading our network at work among a few of the higher end systems. We will be installing a gigabit network.

I'm currently in the process of building a new system which is a Dual Athlon MP 1900+ w/ the Asus A7M266-D motherboard. The board has 2 64-bit and 3 32-bit PCI slots.

I've been looking around at gigabit cards to put into the system and found that Linksys offers both 32 and 64-bit 10/100/1000 cards. My question is, what difference does it make between the two cards? How much of a performance or speed increase would I gain by utilizing a 64-bit card and a 64-bit PCI slot?
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Postposted on Mon Feb 18, 2002 1:02 pm

Don' the number of bits just describe the ethernet adress space. I'm not familiar with that card, but I don't think the number of bits will affect performance. Its more like do you want to have more than 32 bits worth of clients (unlikely), if so you'll need the 64 bit cards.
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Postposted on Mon Feb 18, 2002 1:09 pm

uhhh, no. The 32 vs. 64 bit question refers to the interface between the card and the host PCI bus. It really has nothing to do with "bits of ethernet address space". To answer the question, yes, technically the 64 bit PCI card can be faster than the 32 bit version. After all, it moves twice as much data per clock, and on top of that a lot of 64 bit PCI implementations run at 66 MHz instead of 33. So, the potential is definitely there, but in practice I wouldn't count on seeing 2 to 4 times the throughput. But hey, there's no way to know until you try it. Let us know how it turns out.
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Postposted on Tue Feb 19, 2002 5:03 am

If you're upgrading to GigE because you require the throughput you'll find PCI to become your bottleneck - go for the 64 bit card over the 32 bit card for this reason. The throughput isn't twice as much, but it is a worthwhile increase.

Bruce
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Postposted on Tue Mar 26, 2002 3:12 am

I think this will clarify things a little.

Gigabit ethernet 1000Mb/s = 125MB/s

So if you look at the following table on this page: http://www.pcguide.com/ref/mbsys/buses/ ... dth-c.html

You will see that 32-bit slots will only give you 127MB/s, and when you consider that your SCSI/IDE controller may be on the same bus, well... you are going to be bandwith limited.

64-bit slots double the bits, but also the clock speed to give you 508MB/s....

Now you have to really push yourself to reach that limit... One or two drive won't fill that fat pipe...

You may want to ask yourself... am I actually going to gain anything? or am I just eliminating one or many possible bottlenecks to the ultimate in performance...

You could look at teaming 10/100 nics and saving a considerable about of cost...
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