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Two wired computers, one gets full speed, the other does not

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  • Internet Service Providers
  • Computers
Last response: in Networking
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September 17, 2014 11:09:47 AM

We have two computers connected to a Virgin Media Superhub 2, both wired, both cat5 cables. Across the LAN they both achieve a full 1Gbps (we tested with several movie files) and this computer can achieve the full speed (152 down, 12 up) our ISP promise us. However, the 2nd PC, which is a new build, has struggled to break 40Mbps. The first day I tested it, it managed around 15Mbps down, then 20 with a few config changes. At one point it did manage 60Mbps but very quickly went back below 40 and today it hasn't broken 20.

We have tried different cables, different ports on the modem, changing every config setting we can, re-installing network drivers, a separate network card (which achieved 1Gbps across the LAN again, but the same speeds on speedtest), setting a static IP for the machine in question, turning this one off and testing again but still no change. I've asked our ISP if it could be the modem but they can't find anything wrong with it. We haven't reinstalled Windows as it'd be a pain to set everything up again and it might not even solve the problem. We now suspect it could be the motherboard itself having a physical defect as there are no bios network settings we can find that would cause this.

Specs:

MSI A78M-E35 AMD A78 Socket FM2 micro-ATX with Realtek PCIe GBE family controller
Corsair Vengeance 8GB DDR3 2133MHz Dual Channel
AMD APU A8 - 7600 Socket FM2+ Quad Core
Intel 320 160GB SSD
Windows 7 Enterprise 64-bit

More about : wired computers full speed

September 17, 2014 11:33:05 AM

Tilaron said:
We have two computers connected to a Virgin Media Superhub 2, both wired, both cat5 cables. Across the LAN they both achieve a full 1Gbps (we tested with several movie files) and this computer can achieve the full speed (152 down, 12 up) our ISP promise us. However, the 2nd PC, which is a new build, has struggled to break 40Mbps. The first day I tested it, it managed around 15Mbps down, then 20 with a few config changes. At one point it did manage 60Mbps but very quickly went back below 40 and today it hasn't broken 20.

We have tried different cables, different ports on the modem, changing every config setting we can, re-installing network drivers, a separate network card (which achieved 1Gbps across the LAN again, but the same speeds on speedtest), setting a static IP for the machine in question, turning this one off and testing again but still no change. I've asked our ISP if it could be the modem but they can't find anything wrong with it. We haven't reinstalled Windows as it'd be a pain to set everything up again and it might not even solve the problem. We now suspect it could be the motherboard itself having a physical defect as there are no bios network settings we can find that would cause this.

Specs:

MSI A78M-E35 AMD A78 Socket FM2 micro-ATX with Realtek PCIe GBE family controller
Corsair Vengeance 8GB DDR3 2133MHz Dual Channel
AMD APU A8 - 7600 Socket FM2+ Quad Core
Intel 320 160GB SSD
Windows 7 Enterprise 64-bit


You might try running TCP Optimizer on both machines. It makes it easy to see what the network stack tuning is. Maybe the one machine has had the buffer sizes expanded or something. The forums over at speedguide.net have lots of threads that might be useful.
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September 20, 2014 12:17:47 PM

kanewolf said:
You might try running TCP Optimizer on both machines. It makes it easy to see what the network stack tuning is. Maybe the one machine has had the buffer sizes expanded or something. The forums over at speedguide.net have lots of threads that might be useful.


Sorry for the slow reply: Tried that, it made the problem worse. Now won't go higher than 5Mbps. Resetting it to 'optimal' and windows default both haven't changed it.

What the hell is going on. :( 
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September 20, 2014 5:02:05 PM

Do you have a gigabit Pci card in the new computer? The other computer could use a higher tier card that the new build,
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September 21, 2014 5:38:03 AM

... yes ...
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!