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Video random-access memory (VRAM) is dedicated computer memory used to store the pixels and other graphics data as a framebuffer to be rendered on a computer monitor. [1] It often uses a different technology than other computer memory, in order to be read quickly for display on a screen.
The higher bandwidth used by 80-column text mode results in random short horizontal lines appearing onscreen (known as "snow") if a program writes directly to video memory during screen drawing. The BIOS avoids the problem by only accessing the memory during horizontal retrace, or by temporarily turning off the output during scrolling.
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. This makes it easy to interface with a Video display controller (VDC), which sends a timing signal to the memory and receives data in the correct sequence as it draws the screen.
Each screen character is represented by two bytes aligned as a 16-bit word accessible by the CPU in a single operation. The lower (or character) byte is the actual code point for the current character set, and the higher (or attribute) byte is a bit field used to select various video attributes such as color, blinking, character set, and so forth. [6]
I/O Ports: 1 PC Card Slot, 1 ExpressCard/54 slot (also supports ExpressCard/34), 5-in-1 integrated Digital Media Reader (MMC, SD cards, Memory Stick, Memory Stick Pro, or xD Picture cards), 3 USB 2.0, 1 VGA port, 1 HDMI, 1 RJ11 modem connector, 1 RJ45 Ethernet connector, Expansion Port 3 (for HP xb3000 dock), S-video TV out, 2 headphones-out, 1 ...
Video standards associated with IBM-PC-descended personal computers are shown in the diagram and table below, alongside those of early Macintosh and other makes for comparison. (From the early 1990s onwards, most manufacturers moved over to PC display standards thanks to widely available and affordable hardware). Comparison of video resolutions.
TI-99/2, [45] a 4K RAM, 32K ROM computer with no color, sound, or joystick port and a Mylar keyboard. TI designed the computer in four and a half months to sell for under $100 and compete with the Sinclair ZX81 and Timex Sinclair 1000. Based on the TMS9995 CPU running at 10.7 MHz and with a built-in RF modulator, performance greatly increased ...
There are a number of other companies (AMD, Microchip, Altera, etc.) making specialized chipsets as part of other ICs, and they are not often found in PC hardware (laptop, desktop or server). There are also a number of now defunct companies (like 3com, DEC, SGI) that produced network related chipsets for us in general computers.