The GameBoy Advance

The GBA After the GameBoy Color (GBC) there had to be a newer and better GameBoy. Which was to be the GameBoy Advance. You can see one in the picture on the left. The GBA is a major improvement over the GBC. I mention:

This machine packs a great punch in a small package. The GBA has the same edge connector as the GBC. It has a full GBC chipset inside. In fact, the processor chip of the GBA consists of the full Z80-style GBC processor plus the ARM 7 processor on one die.


Under the hood

GBA processing unit Inside, we see the same kind of filling like in the GBC: just about nothing!

In the center is the Central Processing Unit. It has the Z-80, the ARM-7 and the LCD controller inside. To the left, we see the 4.2 MHz oscillator and to the right is the RAM chip. That's it! The Gameboy does it all with three VLSI chips and an oscillator.


GBA extension slot To the right, we see the extension slot. It is the same as the one in all previous GameBoy's. Power, Ground, 8 data and 16 address lines. Plus some control lines. That's it. The GBA will gladly accept GameBoy cartridges and run with them as well. The GBA senses the kind of cart that is inserted and it will boot with the GBC processor if the cartridge is 'old style'.

If you look carefully in the picture, you see a kind of slotted gap just above the 'U' of 'AGB-CPU-02' on the PCB. This slot is there to accept the case of the cart and to align it with the contact fingers.

Anyway, in the bottom section of the slot is a small tumbler switch. The old GB carts are rectangular at the base. The new GBA carts have an indent there. So old carts push down the tumbler switch and activate the Z-80 style processor in GBC mode. If the switch stays up, the new ARM-7 CPU is booted.


You can witness this by looking at the display during a boot. GBA carts present another logo than the older GBC ones.
In the picture on the left, we see a closeup of the GBA cart-slot. If you look carefully, you can see the small switch that makes the difference


>Using the GBA

The GBA is wonderfull to play with. All the GBC games work 'out of the box', although the colours are quite different. The only drawback is that the pixels are smaller so the height of the image is smaller too. And there are black bars to the left and right of the playing field since the GBA has 250 pixels where the GBC has 'only' 160.

If you press the left shoulder button, the image is stretched to fill the screen horizontally. For some games (like V-rally) this is nice, but Pokemon Pinball gets harder to play. Press the right shoulder button and the image gets narrower again.

To the left we see the content of a GBA game cart. It is filled to the limit! They had to solder the Lithium cell on top of one of the memory chips to get everything in.

Look at the edge connector: it's the same as the one used in the GBC. Still, the ARM CPU is capable of addressing 32 MB of memory without an MBC unit. Apparently some kind of address multiplexing is required. I wonder how they do it...


To the right we see another GBA cart. This one has less crowded filling. It has only two integrated circuits to do it all. No battery required and still it keeps high scores and personal data.

The PCB explains how it's done: there's a 512 KB Flash memory on board. Plus a huge masked ROM. Judging the pincount (44) this must be a very large Read Only Memory. Or, since the ROM's are mostly made by the company that uses the 'MX' brand, this mask ROM is more than just a ROM. Below there is some evidence for this hypothesis.


Look at this game cart. The picture is a bit blurry, but we see the two integrated circuits. One is the big masked ROM again and the other one is a 24LCxx serial EEPROM. This memory will keep the stored data when power is removed. But the serial EEPROM is quite different to approach than a normal 'byte-wide' EEPROM. So some kind of auxilliary processing power or at least some glue logic must be present to handle the parallel - serial conversions. My guess is, that there is an MBC inside each 'Mask ROM' with the MX brand on top. Or at least some kind of additional processor.


Page created December 2005,