A community of homebrew game developers and hardware researchers for the Nintendo Entertainment System (NES) and other retro consoles.| www.nesdev.org
VTxx refers to V.R. Technology's "NES-on-a-chip" Famiclones, some of which having greatly extended capabilities. These capabilities are described in separate articles: VT01 STN Palette VT02+ PRG-ROM Bankswitching VT02+ Video Modes VT02+ CHR Pattern Data Layout VT02+ CHR-ROM Bankswitching VT02+ MMC3...| NESdev Wiki
The PPU generates a video signal for one frame of animation, then it rests for a brief period called vertical blanking. The CPU can load graphics data into the PPU only during this rest period. From NMI to the pre-render scanline, the NTSC NES PPU stays off the bus for 20 scanlines or 2273 cycles. Taking...| NESdev Wiki