If it's the same as the GS605 I have, it's a simple unmanaged switch. There is nothing to configure in the switch, there is no DHCP server in the switch (or is that not what you were asking?).

In reply to a post by ggremlin:

you may even be able to leave xp to get a 169.254.x.y address on each machine, and its autodiscovery to resolve names.

That did work but the PCs couldn't talk to each other, even with the firewalls off, so I ended up assigning static IPs.

In reply to a post by MHC:

That is about what I would expect.

No being familiar with Netgear but is there a possibility you have put it in "Bridge Mode" which means it just acts as a bridge between the Router and remote devices and does not switch locally?

Probably teaching you to suck eggs - but is DHCP off in the Netgear? Are all ports set for Gbit, Full Duplex?

Certainly if PC to PC gives say 250Mbit or above - there could be limitations on disk access which would slow the connection, then you can be confident that the NICs are in reasonable condition.

What if you power off everything, power up the Netgear, wait a minute or two, plug in te two PCs and boot them. What IP addresses do they get? Can they communicate and at what speed.

The switch is a very simple 5 port home gigabit switch so there's no DHCP or bridge mode or any other sort of config, just pure "plug and play". With a direct connection from PC NIC to PC NIC, I copied a 1,164,853,580 byte file in 65 secs which I think equates to around 140 Mbps so the older computer's hard drive could be an issue.

In reply to a post by Anonymous:

Hmmm.

I have a GS605 too.

Or it would be more accurate to say "I had".

It replaced an FS108 8port 100Mbit switch and I had hoped it would increase the speed of large file copies on the LAN. Unfortunately I couldn't see any significant increase in speed, and did see a few unexplained oddities. I took the GS605 out and put the FS108 back, pending further investigation (which isn't likely to happen for a while).

Coincidence?

Given it's price, I'm now thinking that the GS605 isn't going to set the world alight with it's performance which is probably fine in a situtation where high speed is less important and I can get away with speeds of around 150Mbps for streaming media or sharing an internet connection, but if I get a NAS drive, I'm going to need the benefits of gigabit ethernet which means speeds in the order of 700-800Mbps as reported by other posters in this thread.

As has been said, either the switch is the weak link, or the NICs or the PC to which I'm copying the test files. Given that I've taken the switch out of the equation with the direct PC-PC lan link, I'm starting to think that older test PC is just too slow and that's affecting the results - the dedicated LAN Speed Test tool does create a file on the endpoint PC so there's no getting away from hard drive performance.

What I will do is run a test with the newer PC as the endpoint and check the results there.

Yes tests which involve hard disk access that can be a limiting factor, at least until SSDs are the norm, though stuff like iperf should indeed work, not had cause to try it myself so don't know about its options.

With newer NICs they can offload some of the work from the CPU. With older NICs a slower CPU could be tied up servicing the network card (this is where jumbo frames can help, up to a factor of 6 for the larger packets).

To do timed tests with files you could create RAMdisks on both machines (certainly with unix-like boxes some tmpfs sized 0.5 to 1GB would do) - duplicating various sizes of TBB test files makes a suitable collection for this purpose

Whereas to see if the packet rate is affecting the CPU on the older machine you could watch the appropriate tab in task manager / process explorer / system monitor / other utility of your choice throughout the tests.

In reply to a post by joconnell:

Given it's price, I'm now thinking that the GS605 isn't going to set the world alight with it's performance

I had nothing but trouble with my GS605.
Would regularly drop back to fast ethernet on my PC connection although the link to my NAS was OK at Gigabit.
When it was connected as Gigabit I never got more than around 300Mbps speeds.

I have now switched to a Cisco home switch which is rock solid and runs around 700Mbps.

Jumbo frames generally depends on the drivers for the network card - if the adapter properties has some kind of advanced tab or a separate utility (e.g. the Intel Pro stuff).

With a modern operating system there is a default MTU for the interface (usually 1500, but it can take into account if DHCP gives out a different value).
However MTUs to other destinations are reduced on the fly (by PMTUD) as long as the intervening routes allow ICMP (pings and such).

What this means is if all devices on the LAN can cope with jumbo frames you can try it and a modern OS should end up using the larger MTU on the LAN but a smaller value when talking to the internet (*).

You'll want the router to officially support jumbo frames on the LAN interface as it should by design fragment them for a smaller MTU on the WAN interface, even if a device mistakenly tries to send oversize packets towards the internet.

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There are at least 3 factors that might hamper automatic MTU detection / NIC performance:

- If the MTU has been manually tweaked in the past (if there was only a single compromise MTU) the automatic behaviour might have been turned off.

- If a destination site's network admins have block pings (misguided ideas about security) it might take longer to find a working MTU for that path.

- If you have ever used the Windows "detect and repair" network troubleshooter that turns off certain optimisations (favours conservative over speed).

You'll want the router to officially support jumbo frames on the LAN interface as it should by design fragment them for a smaller MTU on the WAN interface, even if a device mistakenly tries to send oversize packets towards the internet

Well the router is a Thomson TG585 v7 with 100Mbps ethernet ports, so jumbo frames don't apply do they? The Netgear GS605 switch (into which the router is plugged in order to share the internet connection) has no config options and the gigabit NICs have jumbo frames disabled (because there are also 100Mbps devices on the network)

Did that and got 88Mbps consistently so it looks like the gigabit switch might be the problem. Next step, try direct connection between PCs.

That sounds like the same problem I had with a GS608.
I replaced it with a cheap Zyxel 8 port switch & Win 7 consistently reports good speeds around 90 - 100MB/sec.

In reply to a post by Als:

That sounds like the same problem I had with a GS608.
I replaced it with a cheap Zyxel 8 port switch & Win 7 consistently reports good speeds around 90 - 100MB/sec.

I take it you mean 90-100 megabytes per sec...