• Please review our updated Terms and Rules here

Trash-80s

C

chuckcmagee

Veteran Member
Joined
Jul 28, 2006
Messages
1,992
Location
Nevada
My uncle purchased a "TRS-80 I" when they first came out. I have been a "geek" all my life so I was excited to spot it during a visit. I WAS NOT IMPRESSED. Because of that, looks like I really missed "the Tandy boat". Now that I am up to my elbows in M100s and M102s and CoCo2s and CCR-81s and CCR-82s and tapes and game cartridges and rca-to-coax cables and cassette cables and joysticks and FD 500/501s, I see that my first impression was incorrect! :satisfie:
 
what are you saying, you have a bunch of old TRS-80 stuff you want to get rid of? Becuase I can help you with that problem if you want :)
 
Get rid of em!! No way, I'm too embarrassed by how much I paid for them to sell them any time soon.
 
My dad when he was in college, dealt with "trash 80's", which he and his friends named them after he wrote a program, and the computer overloaded and basically exploded!!!:) He swears he never did any thing wrong, and I believe him! It's memory probably just couldn't take the heat!
 
Wasn't there a "halt and catch fire" instruction in the model II? It caused a malfunction in the video circuit.
 
There are quite a few undocumented instructions for the Z80, but I don't think any are Considered Harmful. Arguably, the best known 'HCF' instruction is the 6800-family's, which simply toggles the data bus at full CPU speed, and can cause the traces on the pc board to heat up due to bus arbritration issues, sometimes to the point of physical damage to the board.

http://computing-dictionary.thefreedictionary.com/Halt+and+Catch+Fire

--T
 
kb2syd said:
Wasn't there a "halt and catch fire" instruction in the model II? It caused a malfunction in the video circuit.
Click to expand...

Basically it was switching out the video ram that caused that. You could leave the ram 'out' for a maximum of three seconds, if I read the technical reference manual correctly.

Would this be a feature that needs emulating? :D

Aaron
 
AaronBrockbank said:
Basically it was switching out the video ram that caused that. You could leave the ram 'out' for a maximum of three seconds, if I read the technical reference manual correctly.

Would this be a feature that needs emulating? :D

Aaron
Click to expand...

Right, it wasn't a single instruction, but if you switched out the video ram for more than 3 seconds something would let some magic smoke out.

This is a real issue, and not just urban legend.
See:
http://groups.google.com/group/comp...q=model+ii+video+fire&rnum=1#bf36ec0cd2f1d0c6

reply #4 from NSM
 
kb2syd said:
Right, it wasn't a single instruction, but if you switched out the video ram for more than 3 seconds something would let some magic smoke out.

This is a real issue, and not just urban legend.
See:
http://groups.google.com/group/comp...q=model+ii+video+fire&rnum=1#bf36ec0cd2f1d0c6

reply #4 from NSM
Click to expand...

that quote from Neil
NSM said in comp.os.cpm said:
>> Don't forget the Mod II has, IIRC, a nasty video system that can smoke
>> if you misadjust it (which I think could be done in software).
> Yeah, I saw cautions about that.

Yes. It's the only one with the HCF function (Halt and Catch Fire).
Click to expand...

I think he was only kidding about an actual HCF function. There is a caveat somewhere in the Model II documentation about non-display for more than three seconds - I don't have it to hand though.
 
AaronBrockbank said:
that quote from Neil


I think he was only kidding about an actual HCF function. There is a caveat somewhere in the Model II documentation about non-display for more than three seconds - I don't have it to hand though.
Click to expand...

I know it wasn't an actual instruction, but the HCF did work. There are other examples of this with the model II. One is quite long, but I can't find it at the moment.

Kelly
 
I wonder how tempting it would be for a software publisher to include anti-piracy checking routines that end up in a such instruction if the program is not found to be pure? On one hand, it would be their revenge for you running illegal copies. On the other hand, if your computer has broken down, chance is about 0% that you will buy any software. On the third hand, if the cause of malfunction could be traced back to a particular program, the software house might be held responsible and at least lose their reputation, if not being forced to replace the damaged hardware. Or maybe it is the computer manufacturer's issue to prevent the computer not being possible to damage entirely through software.
 
Trust me when i say when the "magical blue smoke" comes out of a computer or any other circuit it ussualy never works again.If you added a CPU cooling fan and put very low resistors on the pins might be able toexted the 3 second period without going below the absalute minimun voltage.Try it it just might work.Let me know you results if you do.
 
something similar happened on the Compucolor. It was really easy to have a bug result in a runaway process and do this accidentally.
 
You must log in or register to reply here.
Back
Top