Transcript LemGen (Linguistic EMulation and Generation ENgine)

EmuCade
An Arcade Game
Emulator
CS491 Project
Spencer Perreault
Overview
Emulation & Video Game Systems
 Host and Target Systems
 Implementation
 Demonstration

What is Emulation?

One device/system imitating another
 Host

and target
Implementations can vary:
 Hardware
or software
 Behavior is paramount
Video Game Systems

Specialized hardware
 Short
life spans
 Wide variety of software

Digital preservation of games
 Playability
on modern machines
 Programmed for specific hardware
Project Goals

Write an emulator
 Compatible
with at least one system
 Reusable components
 Portable
 Full speed
Target System

Space Invaders (Taito, 1978)
 Arcade

classic
Hardware
 Well
documented
 Intel 8080 CPU

8-bit, 2 Mhz
 Few
special circuits
Host System

Closely tied to programming language
 Assembly
for speed
 Sometimes C, C++

Opposite route
 C#,
managed code
 Common Language Runtime (CLR)

Virtual Machine on a Virtual Machine
 Microsoft
Visual Studio 2008
Components
Emulator
Machine
CPU core
Host UI Layer
Memory
Port I/O
CPU Core

Registers
 Pairs
Instruction set
 Instruction loop

 Fetch-Decode-Execute
 Interrupt
handling
Sample Instruction: ADD
// Mnemonic Code
Flags
Description
// ADD S
10000SSS ZSPCA
Add register to A
void OP_ADD(byte src)
{
int result = A + src;
SetFlags(Flags.Carry, (result & 0x100) != 0);
SetFlags(Flags.Auxiliary, ((A ^ src ^ result) & 0x10) != 0);
A = (byte)result;
CalcFlags(A, Flags.Zero | Flags.Sign | Flags.Parity);
}
Memory


Address space
Start and End Address
Size
Description
Read only?
0000h
1FFFh
8K
ROM
Yes
2000h
23FFh
1K
Work RAM
No
2400h
3FFFh
7K
Video RAM
No
4000h
5FFFh
8K
RAM Mirror
Yes
Video RAM
 256x224
monochrome bitmap
Port Input/Output

Button input
 Bits
set to indicate button press
 DIP switches

Sound effects
 Bits
set to trigger sound
 Sounds generated by analog circuits

16-bit shifts
Host UI Layer

Windows form
 Drawing
Read from VRAM
 Rotation and coloration

 Keyboard

events
Mapped to button presses
Execution Procedure
Initialize form and event handlers
 Load Space Invaders ROM

 Virtual

ROM address space
Execute simulated CPU
 Cycle
increments based on frame rate
 Raise interrupts for vertical synchronization

Demonstration
Conclusion

Lessons learned
 Emulation

possible with managed code
Requires optimization
 Testing
is critical
Unit tests
 Debugging

 Pick
an interesting target system
Future Ideas

Implementation
 Optimization

Dynamic recompilation
 Advanced

code generation
Compatibility
 Support
for more machines/games
 Z80 CPU core in progress