Homebrew 3DNES - NES Emulator

[DiscostewSM]

Nice!

I wonder if using a function pointer table over a big switch will improve speed much, though. Compilers generally turn big switch statements into jump tables.

However, something that could give you more speed would be storing the 6502 registers in ARM registers rather than in RAM. lolSnes/blargSnes do it this way, and I think SNemulDS goes even further but I haven't looked into it much. But the overall idea is to do the least RAM accesses possible. I don't know how slow the 3DS RAM is, but on the DS the main RAM is slow as shit, so yeah.

DS RAM is pretty bad. Memory and I/O accesses are delayed to 33Mhz as opposed to 66Mhz (which is only with cache and tcm), and it's further dropped by a hardware glitch that adds 3 wait cycles to all non-sequential access on the NDS9 side, resulting in the bus clock to about 8Mhz.

 

[Abcdfv]

DS RAM is pretty bad. Memory and I/O accesses are delayed to 33Mhz as opposed to 66Mhz (which is only with cache and tcm), and it's further dropped by a hardware glitch that adds 3 wait cycles to all non-sequential access on the NDS9 side, resulting in the bus clock to about 8Mhz.

That actually made me laugh. Though given the constraints of the hardware, I must say the DS devs did a damn fine job.

 

[VMM]

DS RAM is pretty bad. Memory and I/O accesses are delayed to 33Mhz as opposed to 66Mhz (which is only with cache and tcm), and it's further dropped by a hardware glitch that adds 3 wait cycles to all non-sequential access on the NDS9 side, resulting in the bus clock to about 8Mhz.

Is there a benefit for delaying the DS memory frequency?

 

[DiscostewSM]

Is there a benefit for delaying the DS memory frequency?

I don't have the exact details on it, but my belief is that the ARM7 was originally meant to act as the primary CPU, and that the ARM9 was thrown in very late into the R&D phase. Whether this means the DS was to have 2 ARM7s or just one, I don't know, but we do know the ARM7 operates at 33Mhz as the bus does, and from what I understand, the ARM7 isn't affected by the hardware glitch. The DS was meant to be a 3rd pillar, according to Nintendo, so I wouldn't be surprised if their R&D wasn't as "structured" for this project as it has with their other hardware developments.

Anyways, I'm going off-topic here. This thread is about the 3DNES. My apologies.

 

[st4rk]

Nice!

I wonder if using a function pointer table over a big switch will improve speed much, though. Compilers generally turn big switch statements into jump tables.

However, something that could give you more speed would be storing the 6502 registers in ARM registers rather than in RAM. lolSnes/blargSnes do it this way, and I think SNemulDS goes even further but I haven't looked into it much. But the overall idea is to do the least RAM accesses possible. I don't know how slow the 3DS RAM is, but on the DS the main RAM is slow as shit, so yeah.

Exact, i know about the big switch, but i will just do a test if i don't get speed the last way is do what you told, use ARM Registers, i don't know if is possible do it with inline asm, if not, i will try write the CPU in ARM-ASM :C

 

[Coto]

Exact, i know about the big switch, but i will just do a test if i don't get speed the last way is do what you told, use ARM Registers, i don't know if is possible do it with inline asm, if not, i will try write the CPU in ARM-ASM :C

Inline assembly on short functions have been very fast in my opinion. (when reading / writing to dtcm or wram).

Some KEIL (ARM devs) said inline was good for short functions, and it doesn't optimize inlined thumb code if compiler flags are set to do so. The only drawback is that there's no PC, LR or SP management from it (from what I remember..) (this means 0x10 mode for CPSR only)

edit: but the use of labels are permitted, which is nice

 

[st4rk]

Hello everyone, this weekend i will release a new build(if everything continue good), it will include some new features, this will be the 1.8b(2.0 just in Homebrew Loader).


Regards, St4rk.

 

[Doran754]

Hello everyone, this weekend i will release a new build(if everything continue good), it will include some new features, this will be the 1.8b(2.0 just in Homebrew Loader).


Regards, St4rk.

Care to say what these new features are im excited It's fine if you would rather not though.

 

[gamesquest1]

i don't see the relevance, i don't think bugging him about something will make him give you it

 

[Huntereb]

i don't see the relevance, i don't think bugging him about something will make him give you it

I learned that through PM's.

 

[Doran754]

I only asked what the features were didn't exactly demand he release it now or anything, also said it's fine if he'd rather not .. don't see how I bugged him but ok

 

[kyogre123]

I only asked what the features were didn't exactly demand he release it now or anything, also said it's fine if he'd rather not .. don't see how I bugged him but ok

I bet the comment below yours said "gib devmenu pls" before it was edited.

 

[supermalloch]

I bet the comment below yours said "gib devmenu pls" before it was edited.

Nothing was said. It may have been a link to dick wagging on twitter though. However thats off topic for 3DNES...

 

[st4rk]

Hi hi, sorry, i am a busy guy :C

So the new features is the new menu, auto-frameskip, re-worked CPU(it's in WIP), fixing some instruction and timming, support save-state and some issues fixing, i hope i can finish it on weekend :3

I learned that through PM's.

Sorry i forgot you, read now (:

 

[Abcdfv]

Hi hi, sorry, i am a busy guy :C

So the new features is the new menu, auto-frameskip, re-worked CPU(it's in WIP), fixing some instruction and timming, support save-state and some issues fixing, i hope i can finish it on weekend :3


Sorry i forgot you, read now (:

How about me buddy

 

[st4rk]

Sorry guys, it take me more time than i thought, so i need postpone a bit :c

 

[st4rk]

Updates :3

As everyone know, we have some issues with speed in the 3DNES, what i did now:

written unrom in assembly
written CPU with Jump Table
written a configuration menu(in progress yet)
fixing some instructions on CPU
what i will do:
try use GPU on 3DNES(ppu is really the speed problem here)
finish the SaveState/Load Sate
Finish the Menu
Add new mappers(my priority is to Final Fantasy 7 Hack Rom Mapper).
Fix issues on CPU(yeah, there is some little issues in CPU yet).

I hope i can finish it this week XD

 

[kyogre123]

Updates :3

Are you going to use the legendary GPU of the 3DS that everyone else keeps saying it's impossible to implement for homebrew (due to the lack of documentation)?

 

[st4rk]

Are you going to use the legendary GPU of the 3DS that everyone else keeps saying it's impossible to implement for homebrew (due to the lack of documentation)?

Yeah, by the power of macgyver, i will try it.

 

[Huntereb]

Yeah, by the power of macgyver, i will try it.

Shouldn't be too hard to give a couple KB's of the GPU to an NES game!