memory requirements and pixel addressing calculations for arcade game conversions or console emulators. The PC version of Pinball Fantasies has the option to use non-standard modes "high res" modes, such as 640x350, allowing it to display a larger portion of the pinball table on screen. Standard text modes VGA also implements several text modes: 80×25, rendered with a 9×16 pixel font, with an effective resolution of 720×400 40×25, with a 9×16 font, with an effective resolution of 360×400 80×43 or 80×50, with an 8×8 font grid, with an effective resolution of 640×344 or 640×400 pixels. As with the pixel-based graphics modes, additional text modes are possible by programming the VGA correctly, with an overall maximum of about 100×80 cells and an active area spanning about 88×64 cells. One variant that is sometimes seen is 80×30 or 80×60, using an 8×16 or 8×8 font and an effective 640×480 pixel display, which trades use of the more flickery 60 Hz mode for an additional 5 or 10 lines of text and square character blocks (or, at 80×30, square half-blocks). Technical details Unlike the cards that preceded it, which used binary TTL signals to interface with a monitor (or composite, in the case of the CGA), the VGA introduced a video interface using pure analog RGB signals, 0.7 volts peak-to-peak max. In conjunction with an 18-bit RAMDAC this produced a color gamut of 262,144 colors. This gamut has come to be well known as the sRGB color space (but it is most commonly divided into 16,777,216 colors using a 24-bit RAMDAC or 8-bits per primary color). The original VGA specifications follow: Selectable 25.175 MHz or 28.322 MHz master pixel clock Maximum of 640 horizontal pixels in graphics mode, and 720 pixels in text mode Maximum of 480 lines Refresh rates at 60 or 70 Hz Vertical blank interrupt (Not all clone cards support this.) Planar mode: up to 16 colors (4 bit planes) Packed-pixel mode: 256 colors (Mode 13h) Hardware smooth scrolling support No Blitter Supports fast data transfers via "VGA latch" registers Barrel shifter Split screen support Signal timings The intended standard value for the horizontal frequency of VGA's 640×480 mode is exactly double the value used in the NTSC-M video system, as this made it much easier to offer optional TV-out solutions or external VGA-to-TV converter boxes at the time of VGA's development. It is also at least nominally twice that