Double buffering necessarily requires more memory and CPU time than single buffering because of the system memory allocated for the back buffer, the time for the copy operation, and the time waiting for synchronization.
22.
However this was only possible in DOS by directly programming the hardware, and full-featured " hardware acceleration " from the local memory was never implemented on these cards, due to complexities of double buffering.
23.
It provided the ability to interleave data between devices, introduced double buffering, and added support for the Wait-before-transmit ACKnowledgement ( WACK ) and Temporary Text Delay ( TTD ) Binary Synchronous control characters.
24.
During the vertical blanking interval, the driver orders the video card to either rapidly copy the off-screen graphics area into the active display area ( double buffering ), or treat both memory areas as displayable, and simply switch back and forth between them ( page flipping ).
25.
The final part of Carmack's technique was the use of the same EGA hardware features used for scrolling to also implement double buffering : setting up a second buffer into which the code can draw while the first buffer is being shown on screen, which is then switched out during screen refresh.
26.
Most software DVD players do not assist with switching display modes, and even if it is switched manually, they hardly synchronize frame updating with the display's vertical retrace periods . ( There is only soft synchronization using hardware double buffering, which is not enough to match hardware players in the stability of playback .)
27.
The term "'double buffering "'is used for copying data between two buffers for direct memory access ( DMA ) transfers, " not " for enhancing performance, but to meet specific addressing requirements of a device ( esp . 32-bit devices on systems with wider addressing provided via Physical Address Extension ).
28.
:: : That 30 fps would happen if the game was using double buffering; if triple buffering is available the game can ( rather than idle wait for vsync ) render a new frame into a third buffer ( with the confidence that a retrace won't force that buffer to be shown when it's half finished ).
29.
While the actual frame is shown on, the subsequent frame is loaded into a swap buffer page of graphic memory and Amiga switch between the screens istantanely while loading the subsequent frames thanks to its bit-blitter circuit capabilities and the DMA feature of its graphic chipset that could access memory without asking request of the CPU . This technique is called double buffering.
30.
Even with assembler and double buffering, a program to list a deck of cards from the IBM 2501 reader ( 1, 000 cards / minute ) on the line printer could not keep up, as the translation from card hole patterns to EBCDIC for the printer as done by EBPRT was too slow; the more complex ZIPCO and HLEBC were needed instead, as in the example.
