nesdev.org

I would add in support of assembler another thing. IMHO, one of the main reasons it's hard to program in assembler is hardness of revisiting old code. While you work on the current task it looks easy because you keep in mind that every instruction in series is supposed to do. But after a while it's ...

rox_midge wrote: ↑Thu May 07, 2020 7:45 pm Does mapper 4 not support simultaneous PRG-RAM and CHR-RAM?

Yes. Show your header description again, we will check it.

How about heavy metal magic - relaying on hdraw-ignited IRQ, but not waste scanline time, but fill it with useful calculations with fixed clock times (do not cross page boundaries, tune up branches and so on)? So, time will not be wasted and time limit will be reached. ZX Spectrum has modern games w...

What if IRQ handler will be placed in RAM and lda variable will be converted to lda # value which will be updated inplace? Also, extreme variant: do not use Y (or X) register outside IRQ while IRQ can be triggered. So, first instruction of IRQ is stx $2006 and after that X can be used but in the end...

I use this in CA65: ; store_addr dest, addr - save address into word in memory ; To avoid lengthy fragments of the same code: ; lda # < addr ; load LSB of addr ; sta dest ; save to first byte of dest ; lda # > addr ; load MSB of addr ; sta dest + 1 ; save to second byte of dest ; let's define macro ...

... Never use variable++, only ++variable. ... Oh, thanks for hints, especially for this one. I forgot about post-increment complexity completely. This really helps compiler to do inplace pointer increments. I could not understand why so simple thing isn't implemented yet. However, yes, pointer act...

It's interesting for me to compare optimized C code. Let's rewrite it as mentioned above: pass parameters as pointers in zero-page: extern char *src, *dst; #pragma zpsym( "src" ) #pragma zpsym( "dst" ) void str_cpy() { while ( *dst++ = *src++ ); } cc65 -Oirs produces next asm: .i...

although yours have to write pretty bad C for it to be 10 times slower I would say opposite: you have to write pretty bad C code to speed up things. Let's get this typical C code (which is really spirit of C language): void str_cpy( char *dst, char *src ) { while ( *dst++ = *src++ ); } And compile ...

In my opinion/experience 8-bit systems of NES era comply with rule: assemblers produce code with max speed, compilers (like C) are slower by ten times and interpreters (like Basic) are slower than compilers by ten times again. For NES where we have to fit in vdraw/vblank narrow limits it can be seri...

I think in the beginning of Reset Is too short to worry about pending interrupts or whatsoever.
I suppose that any of these two instructions is enough, but both of them eliminates any questions. So why bother?

You should read https://wiki.nesdev.com/w/index.php/PPU_scrolling (if not already). Especially this part: ... Because about 4 pixels of timing jitter are normally unavoidable, $2005 should be written a little bit early (once hblank begins, it is too late). The resulting glitch at the end of the line...

...8K on the parallax tile set... What do you mean by 'parallax tiles'? Parallax as I know usually is per-scanline technique. Do you mean second-background imitation like in Sword Master https://youtu.be/_GSfLqJUcOM?t=64 ? It's done by switching 1k bank of CHR-ROM: http://i93.fastpic.ru/big/2017/09...

Original tutorial contains this bug (at the end of the page): https://taywee.github.io/NerdyNights/ne ... stapp.html
However source code in supplied archive master.zip is correct.
(in light of neighbor topic: another step on the same rake)

I swear to god, despite all evidence to the contrary, that I'm not an idiot. Quote from wiki: If a rake lies in the ground with the teeth facing upwards, as shown on the top picture, and someone accidentally steps on the teeth, the rake's handle can swing rapidly upwards, colliding with the victim'...

Just for your information: loops and increments are cool, simple and fast. But also we need to precalculate these increments and other params to do what we need. And at this point matrix calculus is very useful. This code is example in delphi/free pascal how to render rotozoomed sprites in software:...