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The TMS9918A's method of accessing the video RAM is slower than direct access, as used in unified-memory computers, because accessing video memory involved first outputting the low- then the hi-byte of the (14-bit) video memory address to I/O port $99, then one or more bytes of 8-bit data to port $98.
Dual-ported video RAM (VRAM) is a dual-ported variant of dynamic RAM (DRAM), which was once commonly used to store the framebuffer in graphics adapters.. Dual-ported RAM allows the CPU to read and write data to memory as if it were a conventional DRAM chip, while adding a second port that reads out data.
Many modern GPUs rely on VRAM. In contrast, a GPU that does not use VRAM, and relies instead on system RAM, is said to have a unified memory architecture, or shared graphics memory. System RAM and VRAM have been segregated due to the bandwidth requirements of GPUs, [2] [3] and to achieve lower latency, since VRAM is physically closer to the GPU ...
The term frame buffer is thus often used interchangeably when referring to this RAM. The CPU sends image updates to the video card. The video processor on the card forms a picture of the screen image and stores it in the frame buffer as a large bitmap in RAM. The bitmap in RAM is used by the card to continually refresh the screen image. [15]
Video coprocessors have their own internal CPU dedicated to reading (and writing) their own video RAM (which may be shared with the CPU), and converting the contents of this video RAM to a video signal. The main CPU can give commands to the coprocessor, for example to change the video modes or to manipulate the video RAM contents.
A GART is used as a means of data exchange between the main memory and video memory through which buffers (i.e. paging/swapping) of textures, polygon meshes and other data are loaded, but can also be used to expand the amount of video memory available for systems with only integrated or shared graphics (i.e. no discrete or inbuilt graphics ...
It was designed to be able to allocate an arbitrary space in 8 KB units for a memory space divided into eight. This has made it possible to manage 256 KB of main memory and 128 KB of graphics VRAM, and by enabling free allocation, the software can be mapped by mapping video memory in the same arrangement as other models.
Dual-ported RAM (DPRAM), also called dual-port RAM, is a type of random-access memory (RAM) that can be accessed via two different buses.. A simple dual-port RAM may allow only read access through one of the ports and write access through the other, in which case the same memory location cannot be accessed simultaneously through the ports since a write operation modifies the data and therefore ...