PCjr temporarily freezes cyclically

General discussions on the PCjr

PCjr temporarily freezes cyclically

Postby monzamess » Wed Sep 26, 2018 6:53 pm

Every 30-ish seconds, my PCjr will freeze for about 5-10 seconds, then proceed as normal with no ill side effects (other than ticking me off), even when writing floppy disks.

This behavior just started in the last few hours of usage after the computer sat idle for about a month. It's never done this before and I have not changed the computer's configuration since before the problem started.

I have a lot of variables to consider: jrIDE with a small DOM, two parallel ports (with ethernet and 3.5" floppy connected), speech sidecar, internal modem, power side car.

If I boot with a booter floppy, the behavior doesn't seem to happen so I suppose it's related to one of my add-ons.

I know I should start troubleshooting by eliminating variables but wanted to put this out there for ideas--maybe there is an obvious cause? (just not obvious to me).
monzamess
 
Posts: 66
Joined: Sat Aug 14, 2010 7:16 am

Re: PCjr temporarily freezes cyclically

Postby Brutman » Wed Sep 26, 2018 8:21 pm

What DOS are you using?

The algorithm to determine how much free space is available on a hard drive is terrible on a slow machine like a PCjr. It can cause pauses like what you describe, especially if you are using larger partition sizes. (I notice it above 20 or 30MB.)

Undoubted it is software; hardware rarely does the kind of thing you are describing. Try working from a DOS 2.1 diskette with no device drivers installed except the standard DOS ones. Do not use the jrIDE ... if the machine works for you, then boot using a version of DOS that can see your DOS partitions on the jrIDE. I'm willing to bet you are having the problem with slow performance while computing free space.
Brutman
Site Admin
 
Posts: 1080
Joined: Sat Jun 21, 2008 5:03 pm

Re: PCjr temporarily freezes cyclically

Postby monzamess » Thu Sep 27, 2018 5:07 am

Thanks!

I'm using DOS 3.3.

I'm familiar with the free space delay and encounter it only when I do the first directory listing of a partition. That still happens as expected.

The new behavior pauses the system during any operation--typing at the command prompt, formatting a floppy, drawing in PCPaint, etc...

The only thing that has changed in the machine between "ok" and "not ok" is the passage of time and ticking of the RTC, so I am reluctant to think it's software.

When I get more time I'll systematically go through it and see what I can find.
monzamess
 
Posts: 66
Joined: Sat Aug 14, 2010 7:16 am

Re: PCjr temporarily freezes cyclically

Postby Chuckphd53 » Thu Sep 27, 2018 7:55 am

Try this as an experiment...

Take the top cover off the JR and put a small fan blowing on the Power Supply to cool it down...
just to remove the idea that the power supply needs new caps as they get leaky over the years...
it could be that the power rail(s) is getting noisy...

if at start up the system seems fine then begins to act up trying the fan may offer some understanding.

Is this the Short power supply or the later longer version you have installed in your Jr...

as a second task let the fan blow over the entire system to remove the idea you have a chip issue somewhere..


Chuck
(PCJR/JR-IDE-512DOM,TandyMod,V20-10Chip,BiDir,LPT2,3FlopBrd,
USBEmulator,ZIP100,PS2Keybrd,MouseSysMouse,InternalSwitcherPS)
Chuckphd53
 
Posts: 277
Joined: Sun May 13, 2018 9:15 am
Location: Florida, USA

Re: PCjr temporarily freezes cyclically

Postby KenG » Thu Sep 27, 2018 8:55 am

What is your Ethernet connected to? If the adapter is looking for something that is no longer there, it might cause this behavior.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
Posts: 213
Joined: Sat Jul 16, 2016 5:36 pm
Location: Cincinnati, Ohio

Re: PCjr temporarily freezes cyclically

Postby monzamess » Thu Sep 27, 2018 5:01 pm

Ding ding ding ding, we have a winner. It was the Xircom Ethernet adapter, and/or my ancient wifi router (configured as a switch) that it is plugged into. I can make the behavior come and go by plugging and unplugging the Ethernet cable. I have working Internet access through the router but the pausing keeps happening. I even rebooted and removed the other devices from the router (netbook, Apple II). Oh well, I feel a bit better having narrowed it down to (most likely) an external problem...
monzamess
 
Posts: 66
Joined: Sat Aug 14, 2010 7:16 am

Re: PCjr temporarily freezes cyclically

Postby Brutman » Thu Sep 27, 2018 8:25 pm

That makes no sense.

If you are actively running a networking problem then things like packet loss will make a noticeable glitch in the system. If you are not actively using the Ethernet adapter then it should not be causing any problems; the adapter might try to signal the packet driver that there is an incoming packet, but without a program to intercept it the packet will just be thrown on the floor.

Do you even have the packet driver loaded? What is the minimal number of steps it takes to recreate this? I have a Xircom PE3 on my machine with jrIDE as well and I've never seen what you are describing.
Brutman
Site Admin
 
Posts: 1080
Joined: Sat Jun 21, 2008 5:03 pm

Re: PCjr temporarily freezes cyclically

Postby monzamess » Fri Sep 28, 2018 5:48 am

I get that (mostly, for a guy who doesn't work at the driver-and-below layers).

I have the packet driver in my autoexec; guess I anticipated doing more networking on the jr. Regardless, it's always been loaded when I've used the jr over the last couple of years, but was not a problem until now.

To find the problem, I started with a blank config and autoexec, rebooted, recreated conditions to observe the problem, observed none, then repeated, adding drivers back to config and autoexec one by one. My test was actually to repeatedly dump a text file to the screen and watch for pauses/hang-ups.

In this troubleshooting process, I added the packet driver last based on KenG's suspicion. Then I further narrowed it down to having the Ethernet cable plugged in.

Empirically, I can show that if I load the packet driver but take no further actions to use the network, then while running the text dump loop (or doing anything really), plugging in the network cable introduces irregular pauses to the machine. I did swap out my main router since the last time I used the jr for more than playing booter games... ?
monzamess
 
Posts: 66
Joined: Sat Aug 14, 2010 7:16 am

Re: PCjr temporarily freezes cyclically

Postby Brutman » Fri Sep 28, 2018 7:14 am

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?

What parameters did you use on the packet driver? And what is the exact version number or date string on the packet driver? What DOS and what other device drivers/TSRs do you have loaded?

I'd like to try to recreate this, but it should not be happening. If a packet comes in the Xircom buffers it and then interrupts the machine to get the packet driver's attention. The packet driver then tries to notify software that a packet is available, but if no TCP/IP networking software is running the packet gets dropped on the floor. (Programs like mTCP have to explicitly find and register with the packet driver to get packets, so if you never ran a networking program the packet driver has never been told to pass the packets elsewhere.)

This could be a bug in the specific version of the packet driver you are using. If yours is different than mine then you can try mine.
Brutman
Site Admin
 
Posts: 1080
Joined: Sat Jun 21, 2008 5:03 pm

Re: PCjr temporarily freezes cyclically

Postby Trixter » Fri Sep 28, 2018 7:17 am

Brutman wrote:If a packet comes in the Xircom buffers it and then interrupts the machine to get the packet driver's attention. The packet driver then tries to notify software that a packet is available, but if no TCP/IP networking software is running the packet gets dropped on the floor.


I think his network is sending large regular bursts of traffic to the PCjr, likely some broadcast noise. Even though the packets get dropped to the floor, the driver still has to wake up. This is essentially an unintentional DDOS of the PCjr.

I suggest he run NC to sniff what the PCjr is seeing, and figure out why the Xircom is getting flooded with regular bursts of traffic.
You're all insane and trying to steal my magic bag!
Trixter
 
Posts: 605
Joined: Mon Sep 01, 2008 12:00 am
Location: Illinois, USA

Next

Return to PCjr General Discussion

Who is online

Users browsing this forum: No registered users and 1 guest

cron