Roman Checkers doesn't work anymore!

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pser1
Posts: 1351
Joined: Sun Mar 25, 2012 7:32 pm
Location: Barcelona (SPAIN)

Re: Roman Checkers doesn't work anymore!

Post by pser1 » Fri Oct 18, 2019 8:20 am

Hi,
I am pretty sure it is a problem related to the fact that the game doesn't like the DOS installed when it starts.
The game has a routine that sets to zero all the RAM to be used for graphics from $400 on, so it is using the
working area occupied by the DOS and its buffers. The only way to start the game properly is with the DOS disabled
or not started. I attach here the source of the Switcher I put in my VDK that works falwlessly on my Tano reading the
virtual file from the Drivewire server.
I think that probably using Stephen Woolham DosDetach it should work too.
I will try that later today and will let you know.
regards
pere

Pd for sure this is not a protection scheme, I was wrong while looking for a reason to the problem :-(
Switcher.ZIP
(727 Bytes) Downloaded 53 times

pser1
Posts: 1351
Joined: Sun Mar 25, 2012 7:32 pm
Location: Barcelona (SPAIN)

Re: Roman Checkers doesn't work anymore!

Post by pser1 » Fri Oct 18, 2019 12:16 pm

Hello,
after some tries with the DosMate from Steve Evans/Stephen J Woolham I am just getting
the error you had first found, even on XRoar!
By now, I am unable to start the ROM in an automatic way from inside the 'copier' program.
It seems that there are signs of the DOS as no restart has been done :-(
I think it is not too much trouble having to write EXEC $c000 to start the loaded ROM, so I will
stick to the VDK I loaded that works both on XRoar and on the real Tano
cheers
pere

Pd in case of a succesful try I might try along this weekend, I will let you know
Have a nice weekend!

pser1
Posts: 1351
Joined: Sun Mar 25, 2012 7:32 pm
Location: Barcelona (SPAIN)

Re: Roman Checkers doesn't work anymore!

Post by pser1 » Fri Oct 18, 2019 2:11 pm

well, finally I have had good luck on that subject.
Looking at the cold reset code in the Basic ROM, I have found the place where it calls the interpreter and shows the OK prompt.
So I have modified two bytes more in the Switcher so that now the basic calls the loaded ROM for free, you don't need to issue
any command.
The disk contains:
- ROMAN.BIN this is the ROM (modified by Rolo) with a header to load it at $4000
- SWITCH.BIN is the ml program that switches to MAP1 then patches Basic and makes a cold start
- ROMAN.BAS is a small Basic program that loads the files and execs the switcher
In the attached zip you will find the VDK file and the assembler source code for the Switcher

cheers
pere
RomanCheckers from Disk.ZIP
(6.72 KiB) Downloaded 52 times

fridgemagnet
Posts: 89
Joined: Mon Nov 24, 2014 8:33 pm

Re: Roman Checkers doesn't work anymore!

Post by fridgemagnet » Wed Oct 23, 2019 5:49 pm

Ah, great I shall download it and have a play. Thanks for your efforts, wasn't actually expecting anyone to "fix" it was more pointing out the anomolous behaviour!

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