Vienna Ensemble Pro
Take a look at Vienna Ensemble Pro (VEP, VEPro). There is a Master/Slave feature that let you process VST instruments (and ordinary VST effects) on other computers (and you can mix Macs and PCs).
The master sends MIDI commands to the slave, and the slave returns the result samples. All through a plain cabled ethernet connection.
Here is their own description (from below video):
Vienna Ensemble PRO is the first MIDI and audio LAN solution that
works universally on Macs and PCs, hosting Vienna Instruments as well
as 3rd party 64-bit and 32-bit VSTi/AU plug-ins. Use it as a
master-slave solution with multiple Macs and PCs, all connected with a
simple Ethernet cable, and route the audio streams back to your main
machine without the need of further audio hardware. The intelligent
Preserve function enables you to keep your instruments loaded while
switching from one project to another and with the 64-bit version you
can load as many samples as all of your RAM will hold.
Take a look here (good stuffs around 1 min in..):
Cubase VST System Link
VST System Link allow you to run a complete slave host on other computers, which means you're not constrained to VST/VSTi processing. It is however Cubase only and it may require an additional license. Here is the description (taken from this document):
VST System Link is a network system for digital audio that allows you
to have several computers working together in one large system. Unlike
conventional networks it does not require Ethernet cards, hubs, or
CAT-5 cables; instead it uses the kind of digital audio hardware and
cables you probably already possess in your studio. VST System Link
has been designed to be simple to set up and operate, yet give
enormous flexibility and performance gains in use. It is capable of
linking computers in a “ring” network (the System Link signal is
passed from one machine to the next, and eventually returns to the
first machine). VST System Link can send its networking signal over
any type of digital audio cable, including S/PDIF, ADAT, TDIF, or AES,
as long as each computer in the system is equipped with a suitable
ASIO compatible audio interface. So, why would you want to link up two
or more computers? Well, the added computer power gives you vast
possibilities:
- Dedicate one computer to running VST instruments while recording audio tracks on another.
- If you need lots of audio tracks, you may simply add tracks on another computer.
- You could have one computer serve as a “virtual effect rack”, running CPU-intensive send effect plug-ins only.
- Since you can use VST System Link to connect different VST System Link applications on different platforms, you can take advantage of
effect plug-ins and VST instruments that are specific to certain
programs or platforms. This chapter describes how to set up and use
VST System Link in Cubase SX.