The overall structure of the Abacus system is shown in above Figure. The core of the system is the cluster of 16 dual Pentium-III 450MHz PC based compute nodes, which are connected by a Fast Ethernet switch with 100Mbps links. The front-end node is a dual Pentium-III 500MHz Dell 4300 server with 18 GB of RAID disk storage, which is connected to the Fast Ethernet switch with 1Gbps link. The front-end node is also connected to the Internet through the CityU computer service center network. This is a very efficient configuration to minimize the use of the Internet address and separate heavy network traffic of the computation tasks from the external network. The Abacus is also equipped with a 3x3 display wall using 14" monitors for high-resolution image and video display. The details of the front-node and compute node hardware configurations are listed as below: