Cartridge games on floppy!

Software related questions

Re: Cartridge games on floppy!

Postby alanh » Sun Nov 04, 2018 9:53 pm

Jeff, What exactly did you have to hack? Were the cart images specifically referencing D/E segments? I would (hope) they just used a single flat segment for TEXT (default CS) and placed RAM down in some scratch area in the lower 4-64K range.
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Re: Cartridge games on floppy!

Postby jscrow » Tue Nov 06, 2018 4:11 pm

I didn't see this thread before...Thanks for doing this Hargle! I burned the image to a floppy and was playing Microsurgeon for the first time ever! :D Microsurgeon is my white whale I've been chasing to complete my PCjr cart collection and had no idea what to expect. Great graphics!
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Re: Cartridge games on floppy!

Postby Hargle » Wed Nov 07, 2018 7:20 am

Jeff, What exactly did you have to hack?

There may be specific details in the threads here or the txt file in the archive itself, but it's been a bit too long to really remember. I know a couple of the titles had a minor copy protection mechanism where it overwrote a piece of itself in memory. Since it's a ROM normally, this would be harmless, but once it's sitting in RAM, the game nuked itself. Otherwise a couple minor segment tweaks to get them started and most of them took right off.

jscrow, glad to get that white whale caught!
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Re: Cartridge games on floppy!

Postby adrianblack » Sat Nov 17, 2018 10:15 pm

Hi gents, I was excited to find this disk image to test out on my new PCjr -- but upon trying to load any of the carts from the menu, the computer locks up after a few seconds of loading. (While still displaying the cartridge selection list.)

My PCjr is a 128k Model B -- I wasn't able to find any mention of how much RAM is required for this disk.
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Re: Cartridge games on floppy!

Postby GHiero » Sat Nov 24, 2018 6:55 pm

adrianblack wrote:Hi gents, I was excited to find this disk image to test out on my new PCjr -- but upon trying to load any of the carts from the menu, the computer locks up after a few seconds of loading. (While still displaying the cartridge selection list.)

My PCjr is a 128k Model B -- I wasn't able to find any mention of how much RAM is required for this disk.


I'm pretty sure the disk requires 256KB, which makes sense if you think about how the PCjr works. These games were originally contained on a ROM cartridge that didn't have any slowdown when accessed by the CPU. The floppy loads these games into RAM, so it needs some free RAM to put them into. But it needs RAM that isn't hobbled by slow memory access, so the ROM has to be loaded in RAM above the 128KB mark.
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Re: Cartridge games on floppy!

Postby Hargle » Mon Nov 26, 2018 7:48 am

It would not be difficult at all to create another version of the floppy that uses 0x1000 for the starting segment instead of 0x2000. No idea if there will be a performance hit or if it'll even work, but it's super easy to change- it's 1 line of code in the boot sector. While in there, it would also make sense to do a memory size check and display an error message if it's not going to work. I'll try to get to this in the next few days.
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Re: Cartridge games on floppy!

Postby jscrow » Tue Jan 15, 2019 7:10 pm

It would not be difficult at all to create another version of the floppy that uses 0x1000 for the starting segment instead of 0x2000.


Did you ever get to this Hargle? I would like to test on a 256K PCjr I just setup. When I run the disk on this machine I can't get past the menu.

Thanks
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Re: Cartridge games on floppy!

Postby Hargle » Wed Jan 16, 2019 5:13 pm

Here ya go:

http://www.waste.org/~winkles/jrcartsv5.zip

I have not tested this, all I did was hack the .img file directly to modify the loader address from 2000 to 1000. (a single byte change)
Which means the loader.asm is now out of sync with the .img file for anyone who dares tread in there.

Good luck! If bombs out I'll delete this zip completely so it doesn't spread.
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Re: Cartridge games on floppy!

Postby jscrow » Thu Jan 17, 2019 1:17 pm

I just tested and it did not work. The menu comes up and when I select a game, the drive spins and then nothing happens. I tested on a stock PCjr with a 128KB memory sidecar.

Thanks for creating this version to test. It was worth a try!
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