PCjr temporarily freezes cyclically

[Brutman]

I had thought about packet floods too, but I honestly don't think they are going to be noticeable. My home network is *extremely* noisy and I've never had this kind of problem before. To give you an idea, I packet sniff once in a while and I see all sorts of garbage on the network. Windows 10, a network enabled printer, two Google Home devices, two Chromecast devices, two routers, a PlayStation 4, and more phones and tablets than I can count are all bombarding my network.

The path to service the hardware interrupt and drop the packets is tiny:

• Take the hardware interrupt.
• Scan the list of registered packet handling programs. (Will be 0 in this case.)
• Possibly write to the hardware to tell it to discard the packet.

Anything is possible; the packet driver might be doing more work under the interrupt, including doing things it should not be trying to do. But I've got at least 10 years of experience using these things developing networking code and I've never seen one do this.

[Trixter]

Until the user sniffs and captures traffic, we may never know. "...my ancient wifi router (configured as a switch) that it is plugged into" contributed to my theory.

My theory can be tested by blasting the PCjr with directed traffic and seeing what it does, but I'm at work right now.

[monzamess]

So just to summarize - load the packet driver, but never use a networking problem. Having the Ethernet cable plugged in will cause irregular pauses? And just to be clear, you did not actually run any networking related code except for loading the packet driver?

Yes, exactly.

What parameters did you use on the packet driver? (Etc)

I'll look this weekend and report back.

...figure out why the Xircom is getting flooded with regular bursts of traffic

I do have a surveillance NVR on the network... and a crapton of personal devices (6 people in household with full complement of computers, tablets, game systems, etc). Another thing I will look into.

[monzamess]

Packet driver is "Xircom Pocket Ethernet Adapter III Packet Driver, V.3.08 (940920)"

Confirmed that the computer operates normally plugged into my "local" repurposed switch IF the uplink is unplugged; i.e. errant behavior is due to traffic on the main home network segment hitting the local switch and the PCjr.

I've just started playing with Wireshark. I haven't used this since it was called Ethereal so I'm relearning a few things.

[Brutman]

I just ran a test here and could not reproduce the problem.

I fired up the machine (DOS 3.3), loaded the packet driver, and even ran some programs so the other machines on the network would have the MAC address of the Xircom in their ARP caches. Then I setup a Linux machine to ping at a rate of 100 pings per second. Running the netcat program and just having it wait for an incoming connection, it was able to keep up with the Linux machine for 571 seconds (9.5 minutes) without dropping a single packet. Actual packets sent and received were 48299, which makes it a rate of 75 packets per second (not the desired 100 per second), but that is still amazing.

Then I exited that program, dropped into BASIC, and wrote just a small loop to print increasing numbers on the screen figuring that it would be obvious if the machine paused. The Linux machine was still pinging at 100 packets per second, but now it was not getting responses as no mTCP code was running. No glitches in the BASIC program for 4.5 minutes, so I got bored and gave up.

Perhaps you have some very strange traffic on your network? Or bad hardware.

[Trixter]

icmp ping is only 74 bytes; it's possible he's getting sent MTU maximum. Try larger ping spamming.

[Brutman]

Larger packets would simulate traffic, but I was going for interrupts per second which is the hard part of the test. (There is very little difference between handling an ICMP packet and a larger packet, especially if it is just a matter of dropping the packet on the floor.)

[jscrow]

I'm having the same problem on a jr I just put together with two sidecars.. a jrIDE and bidirectional parallel with a Xircom PE3-10BT. I start getting the temp freezes after loading the packet driver. I've tried changing the driver settings from int=7 to int=0 with same results. I also ran the PE3TEST and the adapter passes everything. I have no issues on my other jr using a Xircom PE3-10BC using the same ethernet cable.

[Brutman]

Ok, two reports now ... I'd still like to see the version of DOS and the exact config.sys, autoexec.bat and PE3 command line parameters that you are both using.

My system machines jscrow's system - a jrIDE and a bi-directional parallel port. I used DOS 3.3 for the test; I'll try DOS 5 next.

[jscrow]

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