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PostPosted: Wed Jun 17, 2015 11:49 am 
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Pin 8 of the Sega Genesis data bus was actually hooked up to something else. You could tell by the fact that it's not syncronized with the rest of the bus, and every other pin is much slower.

https://www.youtube.com/watch?v=yGzgKCsrNHM


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PostPosted: Wed Jun 17, 2015 6:45 pm 
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The video had no insightful information at all in my opinion. And then there were things that were just wrong. He makes a statement that SNES graphics take up more space in RAM, and then moves on to say that had something to do with Genesis being able to scroll faster than the SNES.

But why should anyone expect him to know anything? He's a hardware tinkerer. He's not a programmer.


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PostPosted: Wed Jun 17, 2015 7:35 pm 
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Actual memory bandwidth is a near tie between the two systems. The 68000 is clocked just over twice as fast and has a data bus twice as wide, but taking four cycles to access memory nearly cancels it out.

So the Genesis might be faster, but for reasons other than those mentioned in the video.

  • Super NES mode 1 has to update 3 layers instead of 2. This is probably the closest to "SNES graphics take up more space in RAM," other than perhaps the use of modes 3, 4, and 7 (with 256-color backgrounds) and modes 5 and 6 (with high-resolution tiles).
  • Genesis VDP sprites are a linked list, allowing static allocation to objects with rapid reprioritization rather than having to build OAM and high OAM every frame.
  • To scroll to an area, you must first load the tiles for that area. If your map has different tiles in each part, scrolling faster is possible if you can decompress tiles more quickly. Genesis can decompress faster for two reasons: packed pixels and the video memory FIFO.
  • The developers of Shaq-Fu leaked that Sega charged less per megabit than Nintendo in any given year. In theory, this would let developers get away with using less compression.
  • Slow ROM. Until 120 ns ROM became common, games ran the S-CPU at 3/4 speed.


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PostPosted: Wed Jun 17, 2015 10:41 pm 
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MottZilla wrote:
The video had no insightful information at all in my opinion. And then there were things that were just wrong. He makes a statement that SNES graphics take up more space in RAM, and then moves on to say that had something to do with Genesis being able to scroll faster than the SNES.

But why should anyone expect him to know anything? He's a hardware tinkerer. He's not a programmer.


Is it really that hard to tell that most SNES games do not run at 512x448?


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PostPosted: Thu Jun 18, 2015 12:03 am 
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Yeah, the whole "SNES graphics take more space" logic was just awkward, specially considering that most SNES games use a resolution of 256x224 while most Genesis games use 320x224, making the high-resolution argument completely bogus.

A little bit of research would have shown that the SNES has superior graphics because tiles can use more palettes, the master palette is much bigger, it has more background layers and more special effects (transparency, mode 7, etc.). It has nothing to do with bit depth or resolution.


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PostPosted: Thu Jun 18, 2015 12:43 am 
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I agree with tokumaru, and the ability to scroll faster has nothing to do with the number of layers or colors on screen, because you rarely update 3 layers at 60 fps (or even 30), the 2nd and 3rd are rarely updated and wrap around in most case,but for sure you eat more VRAM .


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PostPosted: Thu Jun 18, 2015 8:39 am 
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"The Genesis scrolls faster than the SNES" is such a stupid myth, and he treats it like it's the abdolute truth. The amount of data involved in scroll updates is peanuts compared to the constant pattern updates that both consoles do. Both are capable of scrolling faster than the human eye is capable of following, and that wouldn't benefit any games.


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PostPosted: Thu Jun 18, 2015 8:50 am 
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The think that annoys me more than anything is when people try to convince others that they know about things they really don't have a clue about.


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PostPosted: Thu Jun 18, 2015 10:15 am 
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tokumaru wrote:
The amount of data involved in scroll updates is peanuts compared to the constant pattern updates that both consoles do.

If your scrolling has become pattern update-bound, and the Genesis can decompress pattern updates faster, then the Genesis can scroll faster.


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PostPosted: Thu Jun 18, 2015 10:44 am 
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tepples wrote:
tokumaru wrote:
The amount of data involved in scroll updates is peanuts compared to the constant pattern updates that both consoles do.

If your scrolling has become pattern update-bound, and the Genesis can decompress pattern updates faster, then the Genesis can scroll faster.

Except when using 16x16 tile mode.


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PostPosted: Thu Jun 18, 2015 11:46 am 
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Quote:
If your scrolling has become pattern update-bound, and the Genesis can decompress pattern updates faster, then the Genesis can scroll faster.

Tiles decompression in sonic is about 3/6 tiles per frame, i don't think this is really incredible .
With 128ko you can decompress most datas before starting each levels .
We must also take in account, the decompressor used before, most of the time was RLE, which is not good with bitplane's graphics and better suited for chunky .

A guy made a lz4 decompressor for the 2 gs,and it's fast as hell :
http://www.brutaldeluxe.fr/products/crossdevtools/lz4/


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PostPosted: Thu Jun 18, 2015 1:12 pm 
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Does Sonic decompress 128x128 rooms as it scrolls, or does it decompress all the 128x128 rooms at the start of the level?


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PostPosted: Thu Jun 18, 2015 6:41 pm 
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TOUKO wrote:
A guy made a lz4 decompressor for the 2 gs,and it's fast as hell

It's just II bad the IIGS can't scroll worth a number II. The dumb frame buffer is in ultraslow E1 RAM and has no tile indirection or starting pixel offset, and there's no memcpy hardware.

But would LZ4 on the Super NES handle planar tiles well?


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PostPosted: Thu Jun 18, 2015 7:29 pm 
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Easy enough to test... Reinterleaved (SNES format, not NES format) 2bpp stuff from the US release of the NES game Batman - Return of the Joker:
Code:
$ ./lz4 reinterleave.bin
Compressed filename will be : reinterleave.bin.lz4
Compressed 262144 bytes into 161555 bytes ==> 61.63%

And using the 4bpp tiles from arcade R-Type:
Code:
$ ./lz4 -9 RTYPE_GFXDATA2.planes
Compressed filename will be : RTYPE_GFXDATA2.planes.lz4
Compressed 131072 bytes into 75309 bytes ==> 57.46%           
$ ./lz4 -9 RTYPE_GFXDATA3.planes
Compressed filename will be : RTYPE_GFXDATA3.planes.lz4
Compressed 131072 bytes into 66957 bytes ==> 51.08%


Last edited by lidnariq on Thu Jun 18, 2015 11:46 pm, edited 1 time in total.

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PostPosted: Thu Jun 18, 2015 8:43 pm 
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lidnariq wrote:
R-Type

Good choice!


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