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Featured Dilemma:

What is Burst and Skip mode in Rev2 & 3 of the C64 DTV ASIC?

Dear Mr Latch,   I read in the programming document that the CPU has a "Burst" and "Skip" mode. What does each do? Sincerly, Éclat De Saut Besançon, France

Dear Éclat ,   Rev2 & 3 of the Commodore64 DTV chip both support SDRAM memories.  In normal operation the DTV accesses memory and only pulls one byte in at a time, but when you enable burst mode the CPU takes advantage of the SDRAM's high speed *sequential* byte reads.  It will pull 4 bytes in the same time normally used to pull 1.  This mode only speeds up SDRAM access and has no effect on flash.  For example:  By making a copy of Basic and Kernal ROM into SDRAM will speed up basic programs considerably.     Skip modes allows the CPU to take advantage of the 32mhz system clock and execute instruction cycles that do not require memory access at full system speed.  Be careful!  This mode will not do dummy accesses often used to acknowledge VIC IRQ's