800XL Black Screen of Death! Help??!!

[dr. kwack]

Two nights ago I was playing some games on my Atari 800XL. I have a 1050 drive hooked up. Played for an hour or so and when I shut off to change games I got a black screen- not booting of the disk, no ready prompt, but the red power light on the keyboard was on. Tried turning on and off a few times- nothing.

 

I turned off for about 20 minutes or so to look up possible problems on line. I came back in and turned it on one last time and voila! It brought up the ready prompt and worked great.

 

Same thing happened again last night. Works great for awhile until it's shut off and then quits. If I let it sit for awhile it comes back on. What gives? Do I need a new power pack? Should I just pick up a new 800XL?

 

Any input would be appreciated!

[andylama]

My 800XL does this too, but I never gave it much thought. I just switch it off, count to 10 slowly, and switch it back on. Works 90% of the time, which seems pretty acceptable to me. Dunno why the XL does this. Considering how cheaply the XLs were engineered (compared to the 400/800 I mean), this doesn't seem surprising.

 

OTOH, My plain old 800 never had this problem. Switch off, exhale, switch on...it boots.

 

In general, it is not a good thing to rapidly cycle power (turn off and back on) on any kind of electronic equipment. It it good to get into the habit of giving the device a moment to cool off, meaning: discharge the capacitors (condensers) etc. Heck, if you're playing with an 8-bit machine, you've already learned lessons in patience...so here's another one.

 

If your XL performs normally in every other respect, most likely, your powerpack is fine and there's really nothing wrong. Just give it a moment to breathe.

[Bryan]

It depends on wether it takes 10 seconds to reboot or several minutes.

 

10 seconds is normal, and it's because of changes Atari made between the 400/800 and the XL/XE. Originally RESET was connected to a pin on Antic, and it triggered an NMI (interrupt signal to the CPU) when it was pressed. In this way, the OS could tell the difference between a "cold" start and a "warm" start.

 

(just so you know... a cold start is where the system is being initialized for the 1st time since being turned off. The system assumes nothing in RAM is valid, and it boots up from scratch. A warm start is where the system assumes that the contents of RAM are valid, and the user simply needed to recover from some sort of non-response situation.)

 

The problem is... if the CPU completely locks-up, then it also stops responding to NMI's, so the Antic method of generating resets was unreliable.

 

Now, on the XL/XE machines, pressing RESET pulls the CPU's reset pin low, causing a power-on condition. The OS now has to determine if the contents of RAM are valid by a different method. It does this by examining 3 "magic" numbers in RAM. These are located at $33D-33F. If these locations contain their post-startup values, then the OS assumes that RESET was pressed, and performs a warm-start. Otherwise, a cold-start is performed.*

 

The next problem is... RAM doesn't always die the instant power is turned off. Some RAM actually takes quite a while to lose it's contents completely, which is why the wait can be fairly long to cold-start an XL/XE machine properly. Sometimes the OS finds the values it's looking for in those 3 locations, while much of RAM has already begun to lose its contents.

 

Anyway, back to the issue at hand... It's normal to have to wait 5-15 seconds. It's not normal to have to wait several minutes. This usually indicates a heat-related malfunction of some sort. My advice would be to reseat the IC's in the machine if they're socketed, and see what happens (or try lifting the computer 8-10 inches above a flat surface and dropping it flat on it's feet for the poor-man's version - this is how many an ST was brought back to life.)

 

-Bry

 

* there's actually a 4th value at location $08 called WARMST which is set to zero during start-up, then set to 255 once the system has started.

[Marius]

The best thing you could do is:

 

Add a 'cold-boot' reset key to your atari 8bit computer. I hear you think: how to do this. At this moment I can not say exactly, but it is very easy to make such a thing by yourself, perhaps another member of this list could explain it.

 

Another thing you could do (this is perhaps more work...) install another OS in your atari... I have changed the atari OS by myself, and with my own OS the atari does a cold-boot when I press shift + reset. This is much BETTER for the health of the atari. My atari is almost never turned off. When I need a coldboot, I simply press start + reset. The fun is: I use a ramdisk very much. When I'm programming my source, assembler, and compiled .obj files are in the ramdisk. When my program causes a 100% computer hangup, I normally had to switch off the computer... and then my ramdisk is cleared ofcourse! Now with this fantastic shift+reset button, my ramdisk is still ok when I reboot the computer.

 

Last option:

 

I really can not guarantee this is a safe way, but this was what I did before, when I had such troubles you wrote about. I turned on the computer. The screen = black as you told me (or the computer is not functionating well, hanging etc.) I insterted a cartridge in the computer (the computer is turned on now). Press reset. Release the cart, press reset again. The computer should reboot now. I really think this is a bad way... and I still think it could damage your computer (some people told me this is not bad... but ok). But it should work.

 

Marius

[dr. kwack]

Thanks everyone! I followed Andylama's advice of switch off and wait and haven't had problems since.

 

A few days ago I received a copy of the 800XL manual in the mail and it actually gave the same advice- Give the machine several seconds before you turn it back on.

 

Thanks again!

[Marius]

That is indeed a good way to do it, but please give the 'cold-boot'-ResetButton a thought too.

 

Once you have this, you'll love it!

 

And it definately saves your equipment.

 

Marius