Mega 1 - four bombs when booting with disk in drive

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jd
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Mega 1 - four bombs when booting with disk in drive

Postby jd » Tue Jun 11, 2019 10:42 am

Hi All,

Was wondering whether anyone could point me in the right direction with troubleshooting the following.

Mega 1 original TOS 1.02 being used as a games machine only with original floppies. This has been working fine, as forever, only this week the following behaviour has been seen.

Switch on machine/reset button with any disk in drive (all working disks as have other ST's to test them on) nearly straight away 4 bombs then flash on screen then 4 bombs again - FREEZE

Switch on machine/reset button with no disk in drive machine eventually boots to desktop where everything is fine, I can run programs/games on same disks that would give 4 bombs if present on restart!!

My problem now is I can't play games that will only boot from disk (i.e. won't start via GEM desktop) so has anyone seen this weird issue with booting with disk in drive. Thanks in advance.

joska
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Re: Mega 1 - four bombs when booting with disk in drive

Postby joska » Tue Jun 11, 2019 11:05 am

Do you have a spare floppy disk? Of so, try formatting it from the desktop and boot with this disk inserted. Does the problem still occur?

Four bombs means that an illegal instruction was encountered. Most games usually boots directly from the boot sector, i.e. TOS will load the bootsector, execute the code in the bootsector which then loads the actual game. If there's a problem with the disk drive there could be read errors when loading the boot sector, and TOS will attempt to execute broken code. Try with a different drive and see what happens. Or there could be a problem with RAM, the loaded bootsector is corrupted. Try a RAM-tester.
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jd
Captain Atari
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Posts: 355
Joined: Thu Nov 09, 2006 12:38 pm
Location: Ruislip, UK

Re: Mega 1 - four bombs when booting with disk in drive

Postby jd » Tue Jun 11, 2019 1:21 pm

Thanks Joska, was about to try your suggestion then I thought about trying a floppy that has an executable bootsector, DBUG's Gauntlet 2 (patched) has a anti-virus bootsector (fcopy one i think), anyways the bootsector did indeed run, displayed its message then DBUG intro came up but then onto GEM Desktop (should've loaded gauntlet).

Switched it all off left it a few moments, now it all works again with no 4 bombs!

Surely a executable bootsector couldn't 'fix' this type of issue as it's been happening for days.

Unless of course it's one of those random 'did nothing' just works for now type thing......

p.s. RAM tester (YART) worked fine, so did GEMBENCH 6 (all when I was getting the 4 bombs with disk in drive). I wonder if the PSU is dying this would be the sort of behaviour expected?

joska
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Re: Mega 1 - four bombs when booting with disk in drive

Postby joska » Tue Jun 11, 2019 1:33 pm

Could it be a random/intermittent problem with the floppy drive? It's 30+ year old mechanical device, at some point it has to stop working.
Jo Even

VanillaMiNT - Firebee - Falcon060 - Milan060 - Falcon040 - MIST - Mega ST - STM - STE - Amiga 600 - Sharp MZ700 - MSX - Amstrad CPC - C64


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