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Old 09 June 2020, 13:00   #1
amigatime
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Noob Question on Booting an Amiga Game from Floppy

Hi guys,

Okay, this is probably going to sound very silly, but as someone who's never booted an Amiga game in his life, I want to make sure I've understood this correctly:

My wife surprised me yesterday by buying Bart Vs. The Space Mutants on disk; clearly she'd been paying attention to the Amiga TV adverts I'd been watching on YouTube! However, Disk A had the write tab closed and booting it (A600) goes straight to AmigaDOS with a '1>' prompt. Am I correct in thinking that this game has been overwritten with something else? Should it just boot straight into the game normally?
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Old 09 June 2020, 13:27   #2
DamienD
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Yup, the game should just boot.

...and I just tested in WinUAE using an A600 config to mnake sure this isn't the issue.
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Old 09 June 2020, 14:37   #3
amigatime
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Quote:
Originally Posted by DamienD View Post
Yup, the game should just boot.

...and I just tested in WinUAE using an A600 config to mnake sure this isn't the issue.
Thanks for confirming, Damien. That's a shame.
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Old 09 June 2020, 14:49   #4
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perhaps you can overwrite such disk with the original game image using powercopy
I don't remember which type of protection have this game
the member dlfrsilver is the expert in this and can tell you if possible
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Old 09 June 2020, 15:09   #5
Fastdruid
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Very common problem was for a virus to overwrite the custom bootcode with a generic AmigaDOS one.

You should always write protect any game unless you need it to be writable and if it needs to be writable it's good practice to leave the Amiga off for at least 30 seconds to ensure there isn't a virus in memory still.

Obviously you should virus check every disk you get as well but by doing things this way it means that even if you _do_ have an infected disk it's unlikely to spread.
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Old 09 June 2020, 21:46   #6
Arnie
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Isn't disk A just the anim disk?
Disk B should boot the game IIRC.
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Old 09 June 2020, 22:09   #7
amigatime
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Isn't disk A just the anim disk?
Disk B should boot the game IIRC.
Hah, it works! And I'm terrible at the game!
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Old 09 June 2020, 23:08   #8
DamienD
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Isn't disk A just the anim disk?
Good point, yes

...but this should still boot automatically.
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Old 10 June 2020, 22:03   #9
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Be aware that Disk A might have a virus on it, and any non-write-protected disk you insert might get infected after you've booted from Disk A. The virus stays resident in memory even during reboots/resets -- you have to physically power off the system long enough for memory to be emptied to stop it from spreading.
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Old 13 June 2020, 18:54   #10
amigatime
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Quote:
Originally Posted by DamienD View Post
Good point, yes

...but this should still boot automatically.
Oh, so Disk A still has an issue of some sort?

Quote:
Originally Posted by AmigaHope View Post
Be aware that Disk A might have a virus on it, and any non-write-protected disk you insert might get infected after you've booted from Disk A. The virus stays resident in memory even during reboots/resets -- you have to physically power off the system long enough for memory to be emptied to stop it from spreading.
Wow, that's some sneaky stuff. Thanks for the warning!
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Old 29 June 2020, 19:38   #11
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Quote:
Originally Posted by amigatime View Post
Oh, so Disk A still has an issue of some sort?



Wow, that's some sneaky stuff. Thanks for the warning!

Yeah, the earliest viruses on the Amiga were bootblock viruses. They'd mimic a normal AmigaOS bootblock, but insert the virus into memory (like TSR programs on MS-DOS) that would periodically run the code. If a writeable device was mounted, it would then try to replicate itself to the bootblock on that device. It would also set itself into the reset vectors so that if you reset the computer it would run the code again, thus surviving reboots.

Many viruses were destructive and would, on triggering some condition, destroy your data. Others were non-destructive and just spread for the entertainment of the author, and not have any bad effects other than displaying a cheeky message after 5 reboots or something.

The problem was that games would often use custom disk formats that used a non-standard bootblock to launch the game code, instead of going into the normal AmigaOS startup sequence. Since the virus writes an altered version of the normal Amiga bootblock to the disk, it overwrites the custom one the game needs to start, thus ruining the disk. This effectively made even "harmless" viruses destructive. The only way to fix a game damaged like this was to find another copy of the game and copy just its bootblock over (and JUST its bootblock, because other parts of the disk often had copy protection).

Of course viruses evolved and there were many later kinds like file viruses (install themselves into executables and spread that way). One widespread and insidious kind were disk-validator viruses which took advantage of the fact that each device could have a copy of its own filesystem integrity checker, which autoran on mounting (kind of like Windows 95 autorun). On those just inserting a disk was enough to load the virus. Fortunately AmigaOS 2.0 and up got rid of this feature.

Anyway if you want to check your disk for a virus, there are numerous Amiga antivirus programs out there on Aminet, like VirusZ and VirusExecutor (most programs use the xvs.library for virus definitions)
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