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Re: repaired games from bad tapes

Posted: Tue May 07, 2019 12:42 pm
by .mad.
while testing FLEX programs, i noticed Sherlock disk detective v2 (Orange) didn't work.
Not sure if it's a USER error or not. :P

i did manage to deprotect the file with a simple 1 byte HEX edit.
and copy it to a FLEX OS disk.

Dragon64 machine/config only.
type BOOT
enter date, then type SHERLOCK

Re: repaired games from bad tapes

Posted: Wed May 08, 2019 10:54 am
by .mad.
Fruity (Impsoft)
fixed 3 problems with this bad dump.
Loading Screen - fixed bad "R" graphic.
Instructions - fixed typo WELCOMBE = WELCOME.
Game - fixed corrupt Reel graphics.

Re: repaired games from bad tapes

Posted: Tue May 14, 2019 3:48 pm
by .mad.
repaired files on this music demo disk.
looks like Microvison put a auto boot loader on the disk after creation, which corrupted the CASCADES.BIN file.

The Pulser version is full of corrupted files and is missing the MENU.BAS and ENVELOPE.BIN.

This version is ok and has the boot loader intact.

Re: repaired games from bad tapes

Posted: Sun May 19, 2019 6:02 pm
by .mad.
Fix for MAME only (it works in Xroar and most likely on real Hardware).
the CAS will not work in MAME as it will not load a BASIC file without a name or header.
it stopped with IO error at the loading pic.

i just put a blank filename and leader gap to make it work.

Re: repaired games from bad tapes

Posted: Sun May 19, 2019 7:54 pm
by robcfg
I’m just wondering, does this one work on a real Dragon?

I think that the Dragon really don’t care that much about a lot of things, and maybe it’s due to a flaw on Mame’s side.

Re: repaired games from bad tapes

Posted: Mon May 20, 2019 11:03 am
by .mad.
robcfg wrote:
Sun May 19, 2019 7:54 pm
I think that the Dragon really don’t care that much about a lot of things, and maybe it’s due to a flaw on Mame’s side.
Yes, I would 100% say it's a MAME problem with the CAS reading routine.
i don't know how to fix / rewrite the MAME code to read the tape loader correctly.
but i know what it needs in the CAS file for MAME to load it. ;)

Re: repaired games from bad tapes

Posted: Mon May 20, 2019 11:44 am
by sixxie
Reading the source (at least, the comments at the top of the source - src/lib/formats/coco_cas.cpp) you can see it does indeed parse the block structure. In theory it's supposed to give up once it hits something that's "wrong", but if it were doing that properly I don't think you'd be seeing these issues...

Re: repaired games from bad tapes

Posted: Mon May 20, 2019 2:54 pm
by robcfg
I think it should just be passing bits to the dac and let the rom load routine take care of that.

Screaming Abdabs comes to mind. It has some standard blocks and then it switches to a custom loader with no standard block structure. Does it load on Mame?

Re: repaired games from bad tapes

Posted: Mon May 20, 2019 4:19 pm
by sixxie
robcfg wrote:
Mon May 20, 2019 2:54 pm
I think it should just be passing bits to the dac and let the rom load routine take care of that.

Screaming Abdabs comes to mind. It has some standard blocks and then it switches to a custom loader with no standard block structure. Does it load on Mame?
It seems to! And that corresponds with the comments - once MAME can't decode the block structure, it feeds them in as sine waves (or "just regular pulses", anyway).

Best guess is that the problem files are down to timing issues - maybe it doesn't back up to the very first bit after the last "proper" block? As in maybe it has already synced to the next block before it switches into "verbatim" mode, which means anything with a delay after MOTOR ON doesn't "see" enough leader before its custom format data begins?

Re: repaired games from bad tapes

Posted: Mon May 20, 2019 5:35 pm
by robcfg
Wouldn't it be having just the "verbatim" mode a good solution?