New Computer having connectivity problems

[starsprez]

Hi,

I purchased a new computer on Ebay. It is an HP 800 G1 SFF with an i5-4570, 4 GB RAM and a 128 GB SSD. The computer looks new and seems to run well....sort of.

I installed Linux Mint 17.1 on it. I have it connected by Ethernet cable to a Westell DSL modem/router. That same device has built in WIFI which is used for other computers and internet appliances through my home.

After the installation I started surfing the web. I noticed that internet connectivity goes away for a couple of minutes and then comes back for a couple of minutes. This keeps repeating and is quite annoying. I disabled all other appliances and computers in the house to check for duplicate IP addresses but the problem remained.

I did some testing and also noticed that if I reboot, about 1 time in 8 the system will lock up where the screen would stay black OR the screen would stay black and you could see and move the mouse cursor.

What is very strange is that both of these problems go away if I disable the WIFI within the router/modem. The computer works perfectly on the internet and boots up every time without incident.

I also noticed that if I disconnect the Ethernet cable, I can also boot up every time. So there seems to be some relationship of between the two.

I'd appreciate any help or suggestions anyone could give.

Thanks,
Paul

[Fornhamfred]

Hi

IMHO i would firstly try a different ethernet cable, try changing the port on the router and if neither of these works try another ethernet card. Also may be worth setting static IP addresses to your various appliances.

[starsprez]

Thanks Fornhamfred..

I haven't tried a different Ethernet cable but at the same time I am getting this computer up and running, I am also getting a Z230 HP workstation up and running. The 2 computers are extremely similar. Both were configured identically but the Z230 works flawlessly. As you might guess, I am doing this on the same desk so all I do is take cables out of one and put them into the other. For that reason, I don't think it is the cable.

I already tried a different port on the router as well as rebooting the router. All other computers on the network work fine.

I haven't tried a static IP address but that may be next. I did try forcing a DNS server (google's at 8.8.8. but that didn't help. I actually turned off all other appliancest be sure there wasn't duplicate IP addresses on the network. It seems that it is the actual router that is somehow making things go wrong.

I'd have to find an Ethernet card to try your other idea.

Paul

[starsprez]

This is the strangest problem that I have ever debugged. The problem is now RESOLVED.

The problem was that internet access would go away every couple of minutes and them come back. It was very annoying and certainly not acceptable. In addition the computer would lock up - either black screen OR black screen with movable mouse cursor every once in a while - usually when logging out or shutting down.

I had the computer connected directly by wire to my DSL modem / router. That same device also had a built in WIFI function which attached 6 or 8 computers and other internet appliances around my home. If I were to disable WIFI, both problems would completely go away. This was so strange.

As opportunity would have, I needed to connect my laptop to the monitor that I was using so I disconnected the DisplayPort wire from HP computer and connected it to my laptop so I could use the external display. Then I connected the analog VGA cable from the HP computer to the external display. This allowed me to use the built in multiplexer within the monitor to switch back and forth between the laptop (DisplayPort) a HP computer (Analog VGA).

It turns out that the problems completely went away! It was the DisplayPort (digital video cable) that was causing the HP computer to misbehave. There must be some sort of PCIe BW limitation or something. I am considering dropping in another 4 GB DIMM to operate the memory subsystem in the HP in dual channel mode to increase memory bandwidth. This may provide the necessary bandwidth to resolve the problem.

Extremely relieved!

Paul

[starsprez]

Hi,

And now the problem is completely RESOLVED. I just put in another 4 GB DIMM. The DisplayPort function was just tested and found to work perfectly. Apparently there was not enough PCIe Bandwidth and when that happens strange things happen!

Now the question is whether this is a Linux Mint thing or not. Could it be a display driver problem? This is as far as I will take it though.

Thanks,
Paul