Editing Macintosh LC 630 DOS Compatible (section)

== Dual Processor Architecture ==

The LC 630 DOS Compatible features a unique dual-processor design allowing true simultaneous operation of two operating systems:

=== Macintosh Processor ===

* '''CPU:''' Motorola 68LC040 @ 33 MHz
* '''FPU:''' None (68LC040 lacks floating-point unit)
* '''Bus Speed:''' 33 MHz
* '''L1 Cache:''' 8 KB integrated
* '''Data Path:''' 32-bit data, 32-bit address

The 68LC040 can be replaced with a full 68040 to add hardware floating-point support.

=== DOS Compatibility Card ===

The DOS Compatibility Card is a two-board assembly that installs in both the CPU socket and the LC PDS slot:<ref>{{cite web |url=https://tidbits.com/1995/06/19/its-a-mac-its-a-pc-its-dos-compatible/ |title=It's a Mac. It's a PC. It's DOS-Compatible! |publisher=TidBITS |date=1995-06-19 |access-date=2026-02-10}}</ref>

* '''CPU:''' Intel 486DX2 @ 66 MHz (or Cyrix equivalent)
* '''FPU:''' Integrated (486DX2 includes FPU)
* '''RAM:''' Dedicated SIMM slot, supports up to 32 MB (ships with 4 MB installed)
* '''Sound:''' SoundBlaster 16-compatible
* '''Game Port:''' PC-compatible joystick port
* '''Video:''' Shares Mac video output (no "hydra" cable required)

Unlike the Houdini II card used in the Power Macintosh 6100, the 630's DOS card shares the Mac's video port directly, simplifying cable management.

=== Card Architecture ===

The DOS card consists of two connected PCBs:
* '''Lower board:''' Plugs into the 68LC040 CPU socket
* '''Upper board:''' Connects to the LC PDS slot
* '''Joystick port:''' Mounted on the PDS connector section

This design leaves the Communication Slot and Video Input slot available for expansion.

=== CPU Upgrade Options ===

The DOS card's 486 socket supports upgrades with proper voltage adaptation:

{| class="wikitable" style="width:70%"
|-
! Upgrade CPU !! Compatibility !! Notes
|-
| Cyrix 5x86-100GP || Compatible || Recommended upgrade
|-
| Intel 486DX4-100 || Problematic || Windows 95 instability reported
|-
| AMD 5x86-133 || Problematic || Requires voltage interposer
|}

Voltage interposers are required for 3.3V processors (original socket supplies 5V). Projects like 486SocketBlaster and 486VRM provide open-source interposer designs.