Let’s see now how the PPU manages to draw stuff on the screen. Moreover, the PPU exposes registers so the game can instruct the PPU how that data is organised (there are many rules, though). The game is in charge of populating the different areas with the correct type of data. The remaining bits will be stored inside the PPU instead, as they will require a faster access rate. Those 8 KB will contain most of the data the PPU will need to render graphics. The PPU has 8 KB of VRAM or ‘Display RAM’, which both PPU and CPU can access directly but not at the same time. Organising the content Memory architecture of the PPU In fact, some special effects achieved thanks to this behaviour will also be supported on the Gameboy. Well, the new PPU doesn’t alter that part, since LCDs require to be refreshed too. However (and for obvious reasons), we got an LCD screen in the Gameboy. If you’ve read the NES article before, you may remember that the PPU was designed to follow the CRT beam. But since the original Gameboy has a green LCD, graphics will look greenish. The picture is displayed in an integrated LCD screen, it has a resolution of 160×144 pixels and shows 4 shades of grey (white, light grey, dark grey and black). This is another component found inside DMG-CPU and it’s actually based on the predecessor’s PPU. The memory map is composed of:Īll graphics calculations are done by the CPU, then the Picture Processing Unit or ‘PPU’ renders them. The SM83 keeps an 8-bit data bus and a 16-bit address bus, so up to 64 KB of memory can be addressed. Notice that this is four times larger than what the NES included. Nintendo fitted 8 KB of RAM for general purpose use (which they call Work RAM or ‘WRAM’). I think explaining them one by one goes beyond the scope of this article, but the main idea is that they optimise certain operations conditioned by the way Nintendo/Sharp arranged the hardware. Although, only bit manipulation instructions are found.įinally, they also added a few new instructions that are not present in either Z80 or 8080. Includes Z80’s extended instruction set.Only 8080’s set of registers are implemented.I’m not certain if that’s just a measure to reduce costs, but one thing for sure is that components will have to be completely memory-mapped.
Neither Z80’s IX and IY registers nor 8080’s IN or OUT instructions are included: This means that I/O ports are not available.The Z80 is itself a superset of the 8080, so what does the SM83 actually has and has not from those two? Having said that, the main processor is a Sharp SM83 and it’s a mix between the Z80 and the Intel 8080. This type of chip is called ‘System On Chip’ (SoC) and the one found on the GameBoy is referred to as DMG-CPU or Sharp LR35902. Instead of placing many off-the-shelf chips on the motherboard, Nintendo opted for a single chip to house (and hide) most of the components, including the CPU.
#DMG GAME BOY PORTABLE#
The Game Boy can be imagined as a portable version of the NES with limited power, but you’ll see that it included very interesting new functionality. Motherboard with important parts labelled Main architecture diagram Note that 'DMG' is the identifier of the original Game Boy model.
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