Supported System Software: 7.5.1, 7.5.3
SCSI: DB-25
Serial Ports: 2
Sound Output: stereo 8 bit.
ADB: 1
Ethernet: use Newer Technology 7ET-L10 or 7ET-C10
Machine Gestalt ID: 98

Minutiae:

Apple sometimes advertises this as a 66 MHz machine, since the clock speed is doubled inside the processor chip.  However, all I/O to the processor is done at 33 MHz. 

Upgraded with one SIMM at a time. Socket closest to CPU (the inner socket) can only accept a single sided SIMM. These SIMMs may be 1MB, 4MB, or 16MB in density. The outside SIMM socket can accept any standard 72-pin SIMM such as 1MB, 2MB, 4MB, 8MB, 16MB or 32MB.  

Has the Apple 486SX PDS card.  Card requires no memory, but can accept a single 72-pin SIMM for maximum DOS/Windows performance.  Use of a dedicated SIMM leaves all Mac motherboard memory available for use with Macintosh software.  486 card can accept 1MB, 2MB, 4MB, 8MB, 16MB, 32MB or 64MB SIMMs which are 80ns or faster.  32MB and 64MB work only with software v 1.0 and PC Card SIMM Patch or with software version 1.5.

Sound output is 16-bit stereo for CD playthrough.  Sound output is 8-bit for Macintosh generated sounds.  Front headphone jack is 16-bit stereo.

Serial Port with the phone icon supports synchronous modems, with handshaking on both output and input supported.

Has 1MB ROM and a 1.44MB SuperDrive.