One important thing to note is that Sprite DMA is actually accomplished by reading the specified values from the specified and writing them to the PPU sprite data port, $2004. The actual operation is just a macro, alternating between reads from $##00-$##FF and writes to $2004 (taking 1 cycle per read/write, as opposed to 4 cycles used on each LDA and STA)

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Quietust
P.S. If you don't get this note, let me know and I'll write you another.