That thing with the blue and magenta ladders (OUT)

[sn3j]

It's not just OUT or CLOSE #4. It's more than that.
This screen is from a bad PRINT #1 with a simple 48K rom:



I recorded it some time ago and can't exactly remember what happened, but I was testing the print routine on #1 with bad AT positions.

[equinox]

but 100% of telling the forum.
See also: KB on Pouet.
Yeah I'm fairly well established.

[equinox]

It's not just OUT or CLOSE #4. It's more than that.
This screen is from a bad PRINT #1 with a simple 48K rom:



I recorded it some time ago and can't exactly remember what happened, but I was testing the print routine on #1 with bad AT positions.

Thanks, that's EXACTLY the thing that I meant (can you see the ladders?). I hope all Speccy nerds recognise it. But seriously.

[sn3j]

There seems to be some 'sweet spot' around the ROM drawing routines that may cause this (and similar looking) crash screen.
I also noticed it's often blue/magenta-ish patterns.
Could definitely trip you up as a kid.

[AndyC]

When playing around with these things, RAM is usually mostly zero. And zero is NOP, so a jump almost anywhere has a high chance of hitting empty space and just running into the data structures up near RAMTOP. I'd hazard a guess that interpreting that as code leads to the sequence of instructions that generates a pattern like this.

[equinox]

There seems to be some 'sweet spot' around the ROM drawing routines that may cause this (and similar looking) crash screen.
I also noticed it's often blue/magenta-ish patterns.
Could definitely trip you up as a kid.

I want to hear more about this. is there just some big fkking NOP park leading to the ROM routine that says "draw magenta and blue ladders".
- Why did they put that there in anyway Ted?
- What Dougal?
- I mean -- you know -- we're priests and all. There's that God and all that, hhahaha.. so why is there the blue and magenta, Ted?
- STUDIO LAUGHTER

[ZXDunny]

I said the hardware can't trigger something like that from a single OUT, but changing a paging register probably causes the machine to crash and display what you remember. Which sounds right to me.

Yeah but the BASIC can and well... it did, y'know? With a single OUT.

[AndyC]

Yeah but the BASIC can and well... it did, y'know? With a single OUT.

Which is why I followed it with a paragraph about what probably happened....

[equinox]

I did get a bit drunk and wild didn't I?
It's okay, this thread has *actual photographic proof* of the Loch Ness OUT-ster. although I'm still not sure why it is blue, magenta, and full of ladders. (I was hoping for something like "due to XYZ reasons, the alternating 0 and 255 ladder patterns are generated blah blah.)
Let us archive this for future Speccy historians. Thanks all.

[equinox]

I want to know why it's ladders -- bytes 0 255 0 255

[MustardTiger]

It looks like a stack crash, some code got caught in an infinite loop and is PUSHing the same six bytes onto the stack over and over.

[equinox]

It looks like a stack crash, some code got caught in an infinite loop and is PUSHing the same six bytes onto the stack over and over.

Why is it blue and magenta and ladders? If someone hired me (like when I used to be a black woman) "please poke a lot of values into tht screen". Even if I just wanted blue and magenta PAPER that would be some work. Ladders seem to be alterate 0 and 255. Why hoW? If I wrote "poke alternately 0, 255, 0, 255, 0, 255.. "that would be ladder.. but why does this happen from teh ROM?

Remember, this isn't one madness, but a real genuine problem that often happened.

[equinox]

Just another bit of fun: how did you first become aware of the existence of 128 PAGES?
Well, I had the crappy stuff that came with the +2 bundle, including the "128K" adventure Blizzard Pass (I could say a lot abuot this weird game, it's harder to run it than a damn demo -- and it really wants USR0 but)
If you cancelled out, or quit, you could sometimes get into 48K paged-out mode. So you could type but you couldn't see what you were typing. The only possible command is BORDER x. Truly, it took me a long time to understand what was going on, back the, when i was about 8 year old. Now i'm 43 and I understand "OK the screen memory is paged out" ohhh boy oh boy

[AndyC]

It looks like a stack crash, some code got caught in an infinite loop and is PUSHing the same six bytes onto the stack over and over.

It's not quite the same six bytes, there looks to be 8 bytes before it repeats in the screen data, but they're different on different lines which is curious. Also the spacing between pink and blue squares doesn't seem to entirely line up with that. I wonder if it's infinitely looping over part of the print string function but pointing at the wrong font and ignoring screen bounds, this spilling out over the attributes?

Would require fiddling around in a debugger and disassembling what happens when you cause a crash to actually make sense of it though and I'm not sure I can be bothered.

Just another bit of fun: how did you first become aware of the existence of 128 PAGES?

Once I read Chapter 8, Part 24 of the +2A manual. Which was not long after opening the box (probably whilst loading one of those crappy Bond light gun games). But then I'm weird like that and was interested in how the extra memory worked, given I knew the Z80 was capped at 64K.

[equinox]

Once I read Chapter 8, Part 24 of the +2A manual. Which was not long after opening the box (probably whilst loading one of those crappy Bond light gun games). But then I'm weird like that and was interested in how the extra memory worked, given I knew the Z80 was capped at 64K.

I was taking the I-Ching program seriously.

I hate the ****ing +2a! What a train wreck!
We should have a puzzle game like Professor Layton.
OK THANKS EQUINOX YOU CAN BACK OFF. sniff... sniff...