One other significant change from the Macintosh SE was the use of 64K bytes of separate dual-ported video RAM to control the internal monitor. Since the video RAM was connected directly to the CPU, there was no need for a video buffer in the memory subsystem. This meant that main memory was not burdened with the additional task of controlling video I/O, unlike the Mac SE's memory subsystem. In the original Mac SE design, the CPU had to interleave its memory access (three out of four cycles) with the video circuitry so that the Mac's screen could be drawn. Thus the SE's CPU could only access memory 75 percent of the time. This arrangement degraded system performance. The separate video RAM in the Mac SE/30 allowed the 68030 processor to access memory at each cycle, which resulted in a big win in performance.
