Espozo wrote:tepples wrote:with an intended range of 128K
Wouldn't this make it an intended range of 256K? Anyway, it seems that the TG16, Genesis, and SNES could have originally intended to have 128KB of VRAM.
At 128 bytes per 16x16 tile, 10 bits cover 128K. The remaining bit is intended for the 2-bit mode and is zero otherwise.
tepples wrote:The VDC was designed to use either fast or slow VRAM.
What, were they unsure?
Yes. Hudson was probably unsure of whether RAM makers would be able to provide fast enough RAM, so it designed in both fast and slow modes. Had RAM makers not hit their target by 1986, the PC Engine would have been specced with slow memory, all games would use slow mode, and then years later, there would be hacks to solder in faster RAM and patch games to alleviate slowdown.
I was about to say how this could be useful to conserve VRAM space, but I'm guessing 4-color tiles apply to everything, not just a certain sprite or something like that...
I'm guessing it'd be like 8x8 or 8x16 pixel sprites on the NES.