GTROM/Cheapocabra mapper for Everdrive N8

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Broke Studio
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GTROM/Cheapocabra mapper for Everdrive N8

Post by Broke Studio » Mon May 13, 2019 12:13 pm

Hi everyone,

Inspired from NovaSquirrel's work here, I added GTROM support to the Everdrive N8.

It doesn't support self-flashing yet, I'll have to add it later.

Don't forget to update your MAPROUT.BIN file in your EDFC folder. (write 0x6F at offset 0x6F)
Attachments
111.zip
Mapper 111 RBF file
(14.12 KiB) Downloaded 514 times
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NOOPr
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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by NOOPr » Mon May 13, 2019 2:54 pm

It's awesome!!

By the way, there's such a implementation of mapper 30 (UNROM 512) out there?

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Memblers
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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by Memblers » Mon May 13, 2019 3:10 pm

That's great, thanks for making that! One day people will be able to release a mapper #111 ROM without fear of people saying "uh, how I do run this?". I think NEScape might might be the first game to use the 8 nametables.

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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by Banshaku » Mon May 13, 2019 5:19 pm

@Memblers

8 nametables? I guess I'm late on the news about mappers? ^^;; How does it work and what it the usage for? I guess there must be a thread on nesdev talking about it? I must have missed it.

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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by tepples » Mon May 13, 2019 6:01 pm

GTROM has two 8K banks of CHR RAM for pattern tables and two 7.75K banks of RAM for nametables. Each nametable bank consists of 4K at $2000 for a four-screen layout plus 3.75K of scratch space at $3000 that can be accessed during vblank or forced blank.

One four-screen layout in nametable bank 0 plus a second in nametable bank 1 equals eight screens.

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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by nesrocks » Mon May 13, 2019 7:23 pm

Yes I think this had been done before, but maybe there are differences in the implementation.
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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by Memblers » Mon May 13, 2019 7:41 pm

Banshaku wrote:@Memblers

8 nametables? I guess I'm late on the news about mappers? ^^;; How does it work and what it the usage for? I guess there must be a thread on nesdev talking about it? I must have missed it.
The main thread is kinda hidden in the Membler Industries section, it's all very disorganized:
https://forums.nesdev.com/viewtopic.php?f=4&t=12716

My original thinking with bankswitched nametables, is that it combines the advantage of 4-screen (being the PPU's native screen size) with the advantage of 1-screen mode (easier to scroll vertically with the status bar being in another bank).

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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by rainwarrior » Mon May 13, 2019 7:54 pm

It's documented on the Wiki too:
https://wiki.nesdev.com/w/index.php/GTROM

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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by Banshaku » Mon May 13, 2019 8:04 pm

@Memblers

Ha, it the specification of your board, wasn't aware of all those details ^^;; I see.

@rainwarrior

I will check the wiki then. Thanks!

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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by thanius » Mon Aug 26, 2019 10:22 am

Hi guys, just got NEScape in my mailbox and after adding the mapper to Everdrive, the screen turns yellow.
Anyone had any luck running NEScape with this mapper?

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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by Broke Studio » Mon Sep 09, 2019 5:05 am

What ROM version did you use ?
Did you dump the game yourself ?
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Re: GTROM/Cheapocabra mapper for Everdrive N8

Post by Bananmos » Tue Sep 10, 2019 3:38 pm

Broke Studio wrote: It doesn't support self-flashing yet, I'll have to add it later.
Feel free to re-purpose the code from my Powerpak mapper30 implementation if it makes things easier for you.

(if I understand the wiki correctly, the self-flashing sequence should be more or less the same on both)

Edit: Oops! You want the Everdrive version of course, and not the Powerpak one.

Though with the Everdrive N8, it might not be worth adding the flash ROM support - as you won't be able to get it to save the written ROM back to the memory card. That's where the easily downloadable and moddable source code of the Powerpak OS really shines.

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