32-bit internal data bus, 256-byte instruction and data caches, Burst-mode RAM access, Built-in memory management unit (MMU).
The Macintosh IIsi computer shares many, but not all of the features of the more powerful [[Macintosh IIci]] computer. Like that of
theMacintosh IIci, the architecture of the Macintosh IIsi is based on the Memory Decode Unit (MDU) and RAM-Based Video (RBV) chips. Key features are the computer’s 20 MHz clock speed, on-board video,sound input capability, flexible expansion ([[NuBus]] or processor-direct slot), custom micro controller that controls the Apple Desktop Bus™ (ADB), real-time clock, soft power control, power-on reset functions, and custom chip that combines [[SCSI]] (Small Computer Systems Interface) and SCC (Serial Communications Controller) functions.