Different broadband speeds - same network?

[TonyGT]

I have 4 PC's connected to the net through the same router. (Billion BiPAC 7300NX)
They are all connected by cable.

All 4 are running Windows 7.

Line: Telkom adsl line - speed is 6mbs.
Data: Web Africa fastest adsl - uncapped.

One PC (quadcore 2.33, 4GB ram, 4 years old) is constantly getting speeds of around 5mbs but the rest vary between 0.6 and 1.3mbs. (Win 7, 64 bit)
The PC with the fastest connection is connected to the router with a 15 meter long network cable. The rest all have cables shorter than 3 meters.

The other Pc's are all newer (less than a year old), with I5 and I7 processors, also with 4GB ram. (Win 7, 32 bit)

Where do I start looking for the cause?

I have tried disconnecting some pc's and have tested with just one pc connected - same results

 

[jc2k-ak]

I have 4 PC's connected to the net through the same router. (Billion BiPAC 7300NX)
They are all connected by cable.

All 4 are running Windows 7.

Line: Telkom adsl line - speed is 6mbs.
Data: Web Africa fastest adsl - uncapped.

One PC (quadcore 2.33, 4GB ram, 4 years old) is constantly getting speeds of around 5mbs but the rest vary between 0.6 and 1.3mbs. (Win 7, 64 bit)
The PC with the fastest connection is connected to the router with a 15 meter long network cable. The rest all have cables shorter than 3 meters.

The other Pc's are all newer (less than a year old), with I5 and I7 processors, also with 4GB ram. (Win 7, 32 bit)

Where do I start looking for the cause?

I have tried disconnecting some pc's and have tested with just one pc connected - same results

I think its your network cards in the PC. Try getting a USB Wifi device, plug it in and test the connection speed. If you notice faster speeds, buy new network cards. I hope it helps.

 

[@udiS3]

I have 4 PC's connected to the net through the same router. (Billion BiPAC 7300NX)
They are all connected by cable.

All 4 are running Windows 7.

Line: Telkom adsl line - speed is 6mbs.
Data: Web Africa fastest adsl - uncapped.

One PC (quadcore 2.33, 4GB ram, 4 years old) is constantly getting speeds of around 5mbs but the rest vary between 0.6 and 1.3mbs. (Win 7, 64 bit)
The PC with the fastest connection is connected to the router with a 15 meter long network cable. The rest all have cables shorter than 3 meters.

The other Pc's are all newer (less than a year old), with I5 and I7 processors, also with 4GB ram. (Win 7, 32 bit)

Where do I start looking for the cause?

I have tried disconnecting some pc's and have tested with just one pc connected - same results

Are your IP addresses statically assigned or is this handled by DHCP?

When you performed the test(s) on the two under-performing machines did you disconnect all other devices from the router? I would try this and see if it makes a difference...

It could also possibly be incorrect MTU settings on one of the router interfaces or the PC Lan interfaces. These should be set to 1500 for ethernet LAN, if not you could find packet fragmentation which will degrade network performance.

 

[dtj]

I have 4 PC's connected to the net through the same router. (Billion BiPAC 7300NX)
They are all connected by cable.

All 4 are running Windows 7.

Line: Telkom adsl line - speed is 6mbs.
Data: Web Africa fastest adsl - uncapped.

One PC (quadcore 2.33, 4GB ram, 4 years old) is constantly getting speeds of around 5mbs but the rest vary between 0.6 and 1.3mbs. (Win 7, 64 bit)
The PC with the fastest connection is connected to the router with a 15 meter long network cable. The rest all have cables shorter than 3 meters.

The other Pc's are all newer (less than a year old), with I5 and I7 processors, also with 4GB ram. (Win 7, 32 bit)

Where do I start looking for the cause?

I have tried disconnecting some pc's and have tested with just one pc connected - same results

Also check if there is any IP entered on the DMZ host option on your router, if so remove it and check the speeds again. The MTU can also make a difference.