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Contended memory: Difference between revisions
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This pattern (6,5,4,3,2,1,0,0) continues until 14463 tstates after interrupt, at which point there is no delay for 96 tstates while the border and horizontal refresh are drawn. The pattern starts again at 14559 tstates and continues for all 192 lines of screen data. After this, there is no delay until the end of the frame as the bottom border and vertical refresh happen, and no delay until 14335 tstates after the start of the next frame as the top border is drawn. | This pattern (6,5,4,3,2,1,0,0) continues until 14463 tstates after interrupt, at which point there is no delay for 96 tstates while the border and horizontal refresh are drawn. The pattern starts again at 14559 tstates and continues for all 192 lines of screen data. After this, there is no delay until the end of the frame as the bottom border and vertical refresh happen, and no delay until 14335 tstates after the start of the next frame as the top border is drawn. | ||
=== 128K / +2 === | === 128K / Grey +2 === | ||
On the 128K and +2 Spectrums, memory pages 1, 3, 5 and 7 are contended. This means that RAM from 0x4000 to 0x7fff is always contended (as memory page 5 is always mapped in there) and RAM from 0xc000 to 0xffff can be contended if page 1, 3, 5 or 7 is paged in there. The 128K and +2 Spectrums also have a different timing pattern from the 48K machine due to their different line and frame lengths: the 6,5,4,3,2,1,0,0 pattern starts 14361 tstates after interrupt, and repeats every 228 tstates rather than 224. | On the 128K and Grey +2 Spectrums, memory pages 1, 3, 5 and 7 are contended. This means that RAM from 0x4000 to 0x7fff is always contended (as memory page 5 is always mapped in there) and RAM from 0xc000 to 0xffff can be contended if page 1, 3, 5 or 7 is paged in there. The 128K and +2 Spectrums also have a different timing pattern from the 48K machine due to their different line and frame lengths: the 6,5,4,3,2,1,0,0 pattern starts 14361 tstates after interrupt, and repeats every 228 tstates rather than 224. | ||
=== Black +2 / +3 === | === Black +2 / +3 === | ||
