Dell WX729 Optiplex 755 LGA775 Motherboard. Dell meets the current and future demands of high performance, power embedded computing, making it ideal for communications, transaction terminal, interactive client, industrial automation applications as well as for standard home use. 

Manufacturer: Dell
Part Number: WX729 0WX729 CN-0WX729
Dell Compatible Part Numbers: DR845 U649C

Specifications:

Chipset
Intel Q35 Express

Supported Processors:
Intel Core 2, Intel vPro, Intel Celeron
 
Memory:
4 x 667-MHz or 800-MHz DDR2 SDRAM, 64-bit operating system: 8 GB Max Total, 32-bit operating system: 4 GB Max Total
 
Audio:
Integrated ADI 1984 High Definition Audio
 
9-Pin Serial Connector
25-Pin Parallel Connector
VGA Monitor Connector
Network/LAN Connector
Six USB 2.0–compliant connectors
Two connectors for line-in/ microphone and line-out; two front-panel connectors for headphones and microphone
PCI 2.3
PCI Express 1.0A
SATA 1.0A and 2.0

Compatible Models: 

Dell Optiplex 755 Desktop Series