VRAM

As a video random access memory (VRAM ) is called DRAM, which took place mainly in the years 1993/94 to the millennium as a local memory on a graphics card application. The most important characteristic of the memory are two ports ( dual-ported RAM), 'normal' for random reading and writing (random access ) and one for sequential read (video signal generation ).

Around the turn of the millennium normal RAM is powerful enough so that normal single - ported RAM (DDR or GDDR ) for graphics cards was sufficient.

It is sometimes incorrectly referred to today with the VRAM memory on a graphics card, regardless of the storage technology.

Construction

VRAM conceptually consists of two parts.

  • SAM (Serial Access Memory) The SAM module ( usually in the form of a shift register ) will not be changed by calculations and includes the read out data from the RAMDAC. It is implemented as a sequential memory, ie, in contrast to the RAM data can only be evaluated sequentially (like a cassette). SAM is much faster to read than RAM, since in principle no address calculations are necessary.
  • DRAM ( Dynamic Random Access Memory ) This memory area is always manipulated by computations for image synthesis. On request, data is copied row by row in the SAM. The local separation parallel read and write access is possible. Technologically, there is a DRAM module either FPM RAM ( 30-40 ns cycle time) or EDO RAM ( 20-30 ns cycle time), which allows clock frequencies of 50-66 MHz.

Developments

  • WRAM (window RAM) is provided similar to VRAM with separate read and write lines, but provides faster access time and is cheaper to manufacture. For example, have the graphics card Matrox MGA Millennium and the Number Nine REVOLUTION 3D " Ticket to Ride" on WRAM.
  • SGRAM (Synchronous Graphics RAM) is a technology with SDRAM related single -ported memory, that is, simultaneous read and write accesses are not possible. It provides an extended range of functions for graphics operations (eg block reading and writing ) and higher clock frequencies.
  • MDRAM ( multi-bank DRAM) is constructed as an independent field memory banks which are connected via a common bus. With this structure, a high degree of parallelism is possible. The graphics card Hercules Dynamite 128 ( GPU: TSENG ET6000 ) has up to 4 MB MDRAM.
  • CDRAM ( DRAM cache ) is a mixture of a static memory (SRAM) and dynamic memory (DRAM). Similar to the cache of modern processors in CDRAM frequently used data in the fast SRAM is stored, which leads to an increase in output.
  • 3D RAM is a development of Mitsubishi consisting of memory blocks with intervening befindlicher integrated logic. For example, some graphics operations ( eg, z - buffer test) are directly executable in memory. Use this memory is in the UltraSPARC by Sun Microsystems.
  • GDDR SDRAM ( Graphics Double Data Rate SDRAM) is a subscription based DDR SDRAM graphics memory, which is characterized by optimized access times and high clock frequencies.
  • Memory module
Semiconductor memory Number Nine Visual Technology Static random-access memory DDR-SDRAM
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