I found this article is true?

konrad

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On the way hardware Neo-Geo draws the scene we will see later, but for now be clear that the Name Table layer patterns / sprites does not work the same way as the other consoles. The other is the Name Table corresponding to Fix Layer, this layer is the layer that has a higher priority in all displayed on screen and unlike the other two do not have scroll and uses a Name Table 40 ラ 28. It is used to draw text, markers of life ... But scoring markers on each of the layers and goeth later.

The other issue to deal with is the system RAM the 68K has allocated about 64KB of RAM and can access up to 1MB memory cartridges containing the program, you can assign up to two banks of 1MB each. ROMS in the cartridge containing the program (not containing graphics or sound data) are called P ROMS inside the cartridges. 68K you can address up to about 24 bits, which translates to a total 16MB memory, however SNK decided that at its console programs occupy as much 2MB.

The next step is the VRAM, unlike Genesis / MegaDrive patterns / sprites are not flushed to the VRAM but are read directly from the cartridge, but it and enter. The size is 64KB because to access that memory is necessary to write on a 16-bit register (one for reading, one for writing) of LSPC-A2 and that makes a total of 64KB. Of these VRAM 64KB to 32KB access only on the organization of the first 32KB and I will come later. The next space of about 16KB RAM corresponds to the color, which gives to a color palette of 16,384 different colors. On how to handle color in Neo-Geo goeth later.

What if that makes this system particularly powerful and above the competition is the Line Buffer, is 2KB two banks each. When the video system is reading a bank to draw the current line the system is drawing on the other, this is a huge advantage over other systems of the time but can not be confused with double buffering. Grace is the Line Buffer is independent of VRAM, this means that the content of the VRAM can be manipulated by the CPU while the LSPC-A2 draws the scene on the Line Buffer.

Furthermore the LSPC-A2 has an MMU that allows up to 24 bits of address to access the memory cartridge. This makes the sides S ROM memory (128KB maximum) and C ROM may have a total size of 16MB. Moreover, in other 16-bit systems patterns / sprites are loaded the cartridge to the VRAM and from there read by the graphics system. Neo-Geo you not, in Neo-Geo could be read directly from the cartridge, that if required a memory interface in the very expensive and composed of many memory chips compared to the other systems of the time cartridges. The LSPC-A2 could no waiting access to the VRAM and the Line Buffer, however you can not say the same cartridge. Patterns / sprites could not be less than 16 pixels horizontally by the fact that this was the time I needed the graphics system to read each of the pixels patterns / sprites cartridge and write on the Line Buffer were about 16 cycles. Since the LSPC-A2 runs about 1536 clock cycles per scan line that are about 96 sprites total of 16 ラ 16. But the screen resolution is 320 pixels, which should give about 20 sprites only. Should not it be the superior resolution? Here the peculiarity of Neo-Geo when rendering the scene and that unlike other contemporary at the same consoles.

For starters are not 96 sprites but 80 since 1536 with time active + HBlank screen, while time active display are about 1280 cycles, this gives a total of 80 Sprites, which are 20 sprites more than correspond by the screen resolution if each of them has a horizontal size of 16 pixels.

The draw-A2 LSPC scenes in three distinct layers ranging from back to front.

Background.
Sprites.
Bookmarks (Fix Layer).
In other systems, what is done is a priority system, so that if you have to draw a pattern / sprite on the screen you look if you have priority over others. In the case of Neo-Geo it is not the case and pulled brute force. This means that a layer on the Line Buffer is drawn, then draws this up re-writing in areas where the top layer takes precedence and leaving the value in those parts where the color is transparent, so on to the last Fix layer is layer. Sprites are background and scroll bearing layers, layer markers does not support it and as I explained above has its own Name Table. Discounting the Layer Fix this means that Neo-Geo has a total of 3 layers (two of sprites and background) to use.

As for color display, Neo-Geo stand up to 256 color palettes of 15 colors + transparent each (4,096 colors on the screen). The first 16 pallets are used by the Fix Layer, the following until the penultimate layer of the sprites and last of all by the background layer.

Since each of the patterns / sprite not turn to the VRAM this have a different use, first know that the LSPC-A2 reads the patterns / sprites from ROM cartridges and writes from the Line Buffer. So for the VRAM system it is used? In other system we have the SAT / OAM call is the attribute table sprites, in the case of MegaDrive this information can store up to 80 patterns / sprites, in the case of a 128. SNES SNES has a total of 256 bytes available for that task ... Neo Geo can use the first 32KB of VRAM for storing not only the Name tables of each of the layers but also to store attribute tables patterns / sprites.

The first 4KB are used for the Fix Name Table Layer, that table does not support scroll and has a conventional organization of 40 ラ 28 8 ラ 8 cells each. In the following Tables 28KB the Name of the planes of scroll and sprite are stored. They could be stored up to 441 tables but as a space for Tables Name it comes down to the 380 tables is needed. this means that a scene in the Neo-Geo can be composed of up to 380 patterns / different sprites. Note that if each pattern / sprite has a size of 16 ラ 16 pixels that are about 280 different sprites on screen at a resolution of 320 ラ 224 pixels. Which means that in Neo-Geo its developers could afford to do scenes where not a single pattern / sprite is not repeated. Each of the tables has a size of 8 bytes and have not miscalculated. What happens is that not only stores the sprite animation table of the current pattern / sprite but this and the next 7 animation frames for the same pattern / sprite. This also allows patterns / animated sprites independently from the rest.
 

Razoola

Divine Hand of the UniBIOS,
Staff member
Joined
Nov 12, 2002
Posts
4,630
The NeoGeo has its limitations just like any other hardware, but what you write above does not make any sense to me due to the bad English. As I have told you before https://wiki.neogeodev.org is the place to go for information on the neogeo which is set out in easy to undetrstand terms if you want to learn about the system.
 

lachlan

drunk downunder!, aka. Muff Diver.,
Joined
Feb 13, 2005
Posts
17,300
I don't have to understand the topic to know this makes absolutely no sense at all.
 
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