The target bitmap in MAME is the same size as the original screeen, every pixel is properly represented. One of the big reasons for this is MAME is software rendered, it allocated a bitmap, it draws, from the original graphic ROMs, to that bitmap.
MAME had been around and emulating Pac-Man and many of those others for almost 15 years by this point, and while the emulation in MAME is always improving, there are certain things it has always got correct, and some of those things this unit falls down on. By you might expect any emulation based Pac-Man unit being put on the market to have perfect emulation of Pac-Man and any other titles included in it. Without modification you cannot move in 8 directions. Xevious, along with Bosconian both highlight one of the major flaws of these Plug and Play units however, they have a 4-way stick. Sound is not yet emulated, but even in silence the volume meter moves, as the test mode demo runs which is curious.
The test mode also shows the build date, has a checksum screen, and even runs a demo of one of the included games, Rally-X, with a volume display, presumably used as part of development. The test mode tells us it runs on GPL hardware. This Pac-Man plug and play unit goes by a number of names, and exists in a number of forms.
