PicoDriveDS v1.5 - Genesis Emulator Port

**Sonny_Jim** · August 24th, 2006, 15:36

Originally Posted by iball

That may be due to the DS itself.
With recent discoveries in obtaining more RAM from the Supercards, if RyanB can harness that same 'supercard-RAM' code then it might be possible in future builds to run larger ROMs.
Of course, it's all up to the developer and I'm sure he's concentrating on speed and sound first.

I'm not a devver nor have I looked at the code, but I'm pretty sure that Picodrive would use the GBA ROM space as READ ONLY memory (this is easy to do) to store the cartridge, and you get 16M of that.

The whole Supercard RAM thing is about writing to it once you have loaded homebrew, reading from it is easy. See my post in the DSLinux expansion for more details.

If Picodrive needed more system ram, it is plausible, but tbh I don't think the megadrive had that much ram in the first place. 256K or something.

(Copied from Wikipedia)

Memory

Boot ROM: 2 KB

* Known as the "Trademark Security System" (TMSS)
* When console is started, it checks the game for certain code given to licensed developers
* Unlicensed games without the code are thus locked out
* If a game is properly licensed, the ROM will display "Produced by or under license from Sega Enterprises Ltd."
* Boot ROM is not present on earlier versions of the Mega Drive and Genesis
* Some earlier games not designed for the TMSS may not work in later consoles

Main RAM: 64 KBytes

* Part of M68000 address space

Video RAM: 64 KBytes

* Cannot be accessed directly by CPU, must be read and written via VDP (Video Display Processor - see below)

Secondary RAM: 8 KBytes

* Part of Z80 address space
* Used as main RAM in Master System compatibility mode

Audio RAM: 8 KBytes

Cartridge memory area: up to 4 MBytes (32 Megabits)

* Part of M68000 address space
* Game cartridges larger than 4 MBytes must use bank switching

**Ryan FB** · August 24th, 2006, 15:59

I'm not a devver nor have I looked at the code, but I'm pretty sure that Picodrive would use the GBA ROM space as READ ONLY memory (this is easy to do) to store the cartridge, and you get 16M of that.

That's planned for the next version, but only for pre-processed appended ROMs. The only reason certain larger ROMs don't work right now is because it has to read them in to main RAM to byteswap them and/or decode from SMD, to get to the internal format Picodrive uses. The plan is to write a PC-side tool which will do this, so ROMs which are preprocessed can be read directly from GBA ROM space without hitting main RAM. This should allow some of the 4MB ROMs to work.

**The Hombrew Hunter** · August 24th, 2006, 16:32

Awesome. I'll wait for the massive UMK3 hack to work, hehe.

Can't wait for next version!

**Deburner** · August 24th, 2006, 20:09

so much better than the last version

**nickmasterx** · August 25th, 2006, 02:51

Originally Posted by Talka1ot

Why are you people asking if it works. Just try it out yourselves.

I haven't yet, I really only want Gunstar and Sonic, maybe SF and MK. Thats it realy. So it may not be worth the hastle, yet.

Because I don't see .nds file for supercard. How do I go about making a .nds?

**Bonic** · August 25th, 2006, 05:30

Does this thing work of MMD yet? I cant get Sonic 1 working

**Aldrikh** · August 25th, 2006, 07:25

Added support for appended ROMs. This should allow users with carts not supported by gba_nds_fat to use PicoDriveDS.

unfortunately, it still doesn't work with ewin2 (either that, or i can't copy/paste a command line, but i think it's ok :-))

i just get some text (one line at the top of the bottom screen) and then black screen ... (and i've no idea what is written, 'cause the line just disapear almost instantly)