Introduction
The Texas Instruments TI-99/4 was released in 1979. It ran on the TMS9900 microprocessor, a 16-bit processor. The machine had an advanced TMS9919 Video Display Processor that could produce 256x192 pixels in 16 colors and was capable of hardware sprites. This same chip is used in the MSX1 line of computers
The computer had a calculator style keyboard that made typing on it hard. One of the unique features of the system was the expansion system. Texas Instruments produced a Peripheral Expansion System box to contain hardware add-ons. Despite the advanced nature of the hardware, Texas Instruments insisted on remaining the sole publisher of software, which caused developers to focus on the competing systems such as Atari and Commodore.
Another problem with the system is that the RAM was shared with the VDP. To run the full screen capabilities with sprites and 16 colors, the VDP needs 16KByte of memory. But that is all the computer has. It does have 256 bytes of scratch pad RAM, which has the same role as registers in other CPU architectures. So when loading a BASIC program, not all of the features of the video chip could be used due to lack of memory. Memory expansion units were for sale driving up cost for the user.
TMS9918 Series Video Display Processor (99n8, 99n9, 91n8, 91n9)
The TMS9918 is a series of video display controllers (VDC) manufactured in 1979 by Texas Instruments, also refered to as 'Video Display Processor' (VDP). The TMS9918 and its variants were used in the ColecoVision, CreatiVision, Memotech MTX, MSX, NABU Personal Computer, SG-1000/SC-3000, Spectravideo SV-318, Spectravideo SV-328, Sord M5, Tatung Einstein, Texas Instruments TI-99/4, Casio PV-2000, Coleco Adam, Hanimex Pencil II, and Tomy Tutor.
Key Features:
- 256x192 pattern based color pixels per screen
- 16 different colors
- 8-bit memory mapped CPU interface
- No need for DMA, CPU can access VRAM
- 32 single color Sprites per screen (4 per scanline)
Variants:
- TMS9918A - 60Hz output, NTSC video
- TMS9928A - 60Hz output, YPbPr video
- TMS9929A - 50Hz output, YPbPr video
- TMS9118 - Different RAM than TMS9918A, otherwise identical
- TMS9128 - Different RAM than TMS9928A, otherwise identical
- TMS9129 - Different RAM than TMS9929A, otherwise identical
VRAM: 16kB Sound Chip TMS9919, later models used SN94624 Sound 3 voices, 1 white/periodic noise Display Chip TMS9919, later models used SN94624 Display 40x24 text
32x24 16 color text, pattern based
256x192 16 color, 2 color per 8 pix. Best Text 40x24 Best Color 16 colors (2 per 8 pixels) Best Graphics 256x192 in 16 colors Sprites 1 color, 16x16, 4/scanline, 32 total Original Price $1150