The basic principles of GhostCast over IP multicast (which has been a standard part of TCP/IP for almost 20 years now) is described here.

There can be any number of causes for multicast performance problems or failure; the most common one, far and away above all others, is networks that are misconfigured. If multicast fails outright the cause is usually a misconfigured switch or router - poor performance is usually caused by unmanaged switches (which treat multicast as broadcast) or managed switches without IGMP snooping enabled (which again causes the switch to treat multicast as broadcast) mixed in with ancient Half-duplex or 10-megabit gear which causes collision problems for the network segment where the problem equipment is.

However, for this kind of poor performance in older editions of Ghost like 8.0 another common cause is a problem in the endpoints themselves; this is especially a problem with never machines which are not designed to be compatible with DOS drivers, and which place the hard disk and network driver interrupt lines together. To see if this is affecting the T61, try adding -noide to Ghost to force it to use the system BIOS to access the hard disk instead of using its own built-in disk drivers (which require the IRQ line to not be shared with the network device).