Xserve G4

The Xserve G4 was released on May 14, 2002.

It has a PowerPC G4 CPU at 1000MHz with a integrated FPU.

Also, it has 32MB of DDR SDRAM, with 256MB of PC2100 DDR SDRAM, which is expandable to 2000MB.

It had a 60GB 7200RPM HDD and runs Mac OS X Server 10.1.5 and is upgradable to Mac OS X Server 10.5.8.

Xserve G4 Cluster Node

The Xserve G4 Cluster Node was released on March 1, 2003.

It has a Dual-core PowerPC G4 CPU at 1330MHz with a integrated FPU.

Also, it has 256MB of PC2700 DDR SDRAM, which is expandable to 2000MB with 60GB 7200RPM HDD and runs Mac OS X Server 10.2.4 and is upgradable to Mac OS X Server 10.5.8.

Xserve G5

The Xserve G5 was released on January 6, 2004.

It has a Dual-core PowerPC G5 CPU at 2000MHz with a integrated FPU.

Also, it has 512 or 1000MB of PC3200 EEC SDRAM, which is expandable to 8000 or 16000MB, depending on the model,  and also has 80GB of 7200RPM HDD and runs Mac OS X Server 10.3 and is upgradable to Mac OS X Server 10.5.8.

Xserve G5 Cluster Node

The Xserve G5 Cluster Node was released on January 6, 2004.

It has a Dual-core PowerPC G5 CPU at 2000MHz with a integrated FPU.

Also, it has 1000MB of PC3200 EEC SDRAM, which is expandable to 8000MB,  and also has 80GB of 7200RPM HDD and runs Mac OS X Server 10.3 and is upgradable to Mac OS X Server 10.5.8.

Xserve Xeon 2006

The Xserve Xeon 2006 Model was released on August 7, 2006.

It has a Dual-Core Intel Xeon 5160 CPU at 3GHz with a integrated FPU.

Also, it has 1GB of ECC DDR2 FB-DIMM, which is expandable to 32GB, and also has 80GB of 7200RPM SATA and runs Mac OS X Server 10.4.8 which is upgradable to Mac OS X Server 10.7.5.

Xserve Xeon Nehalem

The Xserve Xeon Nehalem Model was released on April 7, 2009.

It has a Quad-Core Intel Xeon X5570 CPU at 2.93GHz, which can be Turbo Boosted to 3.33GHz.

Also, it has 3GB of DDR3 ECC SDRAM, which is expandable to 96GB, and also has 160GB of 7200RPM SATA and runs Mac OS X Server 10.5.6 which is upgradable to Mac OS X Server 10.11.5.