intel D865GLC pci bus

[torledo]

Hi all

We've got a number of P4 machines that use the intel D865GLC motherboard, and we'd like to install intel 1000GT gigabit adapters in them. While the adapters are compatible the D865GLC doesn't appear to have any 64bit PCI slots....

i've read that could be a problem when using gigabit because of the risk of saturating the PCI bus. Don't know if that's true or whether 64bit vs 32bit PCI is an issue for gigabit to the desktop,

Any knowledge ?

[Geoff]

The bandwidth of the standard 32bit PCI bus is 1.1Gbit. So basically, it'll be fine as long as you weren't planning on doing anything else with the PCI bus as well.

[torledo]

does the usb connection also share the same bus as any PCI expansion cards, if so i'd imagine any usb or firewire activity could potentially affect performance of the gigabit adapter.

[Geoff]

Probably. It depends on how the chipset does it. Other candidates include your IDE/SATA bus, and any onboard sound/graphics/network.

If you go into device manager and 'view by connection' it'll tell you whats hanging off your PCI bus.

[torledo]

Thanks a lot geoff..

here's a screen grab of the device manager on the PC's with devices on the PCI bus.

PCI.jpg

I'm guessing the hard drive/CDROM drive are connected to a minimum at ATA66 so in theory that's 66 MB/s or half the PCI bus bandwidth for the internal hard disk alone!!!!, sound i'd have no idea what kind of badwidth that could be using, most worrying is the precense of AGP8x on the PCI bus - the geforce MX440 in therory could use 2133MB/s.

Have i got my maths all wrong and there is infact plenty of bandwidth for a gigabit network adapter, and have i misintepreted the presense of AGP8x. We've had to use a Geforce MX440 because one of our teaching apps won't work with the integrated adapter, but that's soon to be remedied so that we can actually use the integrated adapter instead. Would using an integrated grafx adapter ease the badnwidth worries.

It's a real shame that the PCI bus isn't 66mhz as that would give over 2gbps

Any ideas/suggestions, should i just stick with the 10/100 Pro VE adapter instead ?

[Geoff]

AGP uses DMA. DMA transfers do not impact your PCI bandwidth nearly as much as the CPU is not involved. The same is true for your HDD(s).

I'm wondering why you need 1Gbit in these machines? What's the use case for it? Why are 100mbit cards not sufficient?

[torledo]

AGP uses DMA. DMA transfers do not impact your PCI bandwidth nearly as much as the CPU is not involved. The same is true for your HDD(s).

I'm wondering why you need 1Gbit in these machines? What's the use case for it? Why are 100mbit cards not sufficient?

At the moment 100meg is sufficient, but i'm just thinking ahead for future proofing for applications such as OS streaming. Even then 1000mbps isn't a necessity but it'd be handy to know that if 1gbps is required we've got the hardware in the D865GLC pc's that can handle it.

[Michael]

Installing Gigabit network adapters into a 32Bit PCI slot will not improve performance that much in practice.

Most newer hardware come complete with onboard Gigabit adapters, so in the longterm it would be more beneficial to buy new systems/motherboards. All new motherboards come built on PCI-Express which is much faster than standard PCI.

Of course the other expense you have is ensuring you have Gigabit switches everywhere. They're a lot more affordable these days, but still need to be planned in your purchasing.

[Geoff]

At the moment 100meg is sufficient, but i'm just thinking ahead for future proofing for applications such as OS streaming. Even then 1000mbps isn't a necessity but it'd be handy to know that if 1gbps is required we've got the hardware in the D865GLC pc's that can handle it.

Ah I see. Well there is no harm in trying. Like I explain it really depends on the I/O load as to what degree it will work. Personally I've only seen issues on servers, where the system load is heavier/different.

If you are interested in future proofing, you might want to mandate onboard 1Gbit networking in all your new desktop pc purchases though. But if you're buying PCI Express based systems like we are (various HP AMD64 models) you'll get that as standard anyway.

[torledo]

Ah I see. Well there is no harm in trying. Like I explain it really depends on the I/O load as to what degree it will work. Personally I've only seen issues on servers, where the system load is heavier/different.

If you are interested in future proofing, you might want to mandate onboard 1Gbit networking in all your new desktop pc purchases though. But if you're buying PCI Express based systems like we are (various HP AMD64 models) you'll get that as standard anyway.

Good points geoff, any new PC's we have mandated onboard gigabit ethernet, and as you've said it's pretty much a standard nowadays.

The P4's have served us really well and it would be nice to bring them up-to-date with gigabit so that we can get two or three more years out of them. I'd imagine we would still get atleast another 18 months out of them if we did nothing.

@Michael - i'm not concerned about the cost of gigabit switches, or of migrating to gigabit overall. I agree that to get the best gigabit performance new PCIexpress based machines is definitely the way to go. But while the budget is there for gigabit switches it isn't for replacing dozens of P4's, so i'm hoping that i would see some improvement in network performance with 1gbps adapters on standard 1.1gbps PCI bus.

[Geoff]

I'm hoping that i would see some improvement in network performance with 1gbps adapters on standard 1.1gbps PCI bus.

While it's impossible for you to get the 'full' 1Gbit speed out of the NIC you will certainly get more than 100Mbit. Exactly how much depends on what the machine is doing and where the PCI bus bandwidth is being utilised at the time. So if you can justify the not-quite-but-not-far-off performance vs the cost then it's a reasonable upgrade despite the hardware limitations.

There is one slight gotcha that you may run into depending on the components in use. Some motherboards have a tendency to lock up when you max out the PCI bus, leading to a BSOD. You may wish to grab one of your P4's and test it to destruction with a 1Gbit card installed to check if this is the case with your machines.