Texas Instruments TMS9918

The TMS9918 is a Video Display Controller (VDC) manufactured by Texas Instruments, introduced in 1979, with several variants manufactured in the 1980s. It was used in the Texas Instruments TI-99/4, with variants used for the ColecoVision and Sega SG-1000 games consoles and most MSX computers. Modified versions were used in some arcade game system boards, and it was the basis for the VDP in the Sega Master System console, as well as the Sega Game Gear handheld.

The TMS9918 and its variants were used in systems such as ColecoVision and CreatiVision (a Japanese variant), Memotech MTX, MSX, Sega SG-1000/SC-3000, Spectravideo, Sord M5, Tatung Einstein, Texas Instruments TI-99/4, Casio PV-2000 and Tomy Tutor/Pyuuta.

The TMS9918 has two separate and independent graphic types that do not interact:

Both of these are discussed in more detail in their respective sections below.

There are several variants called TMS9918, TMS9918A, TMS9928A and TMS9929A, where the 'A' indicates a second version of the chip which added new features, most prominently the addition of a bitmap mode (Graphic II). The non-A version was only used in the TI-99/4; the TI-99/4A and the other computers had the A version VDC. The TMS9918A and TMS9928A output a 60 Hz video signal, while the TMS9929A outputs 50 Hz. The difference between '1' and the '2' in 'TMS9918A' and 'TMS9928A' is that the '1' version outputs composite NTSC video, while the '2' versions (including the TMS9929A) outputs YPbPr, more precisely the Y, R-Y and B-Y colour differences (luminance and colour difference signals). The need for the latter was predominant in the 50 Hz world, including Europe, due to the different video signal standards PAL and SECAM. It was more cost-effective to output Y, R-Y and B-Y and encode them into PAL or SECAM in the RF modulator, than to try to have a different console for every different color standard. The '1' version also features an external composite video input which made it a handy chip to use in video "titlers" that could overlay text or graphics on video, while the '2' version does not.

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