But with a mainframe budget, simply rolling out the usual Apple solution of OS X boxes for each of the users becomes feasible, too. If you also have a mainframe-class budget to go with the request, then many things can become more easily possible. Gigabit Ethermet and USB and related I/O buses are nowhere near that fast, which is why having more than a few ARD or VNC sessions becomes problematic. For comparison, Thunderbolt 1 can run at 10 gigabits per second, and Thunderbolt 2 at 20 gigabits per second. These same bandwidth and latency limits hit approaches based on X11, ARD and VNC, too, though those usually don't run at Thunderbolt Display resolutions. Resources and slots which aren't available. You can end up saturating a gigabit network in fairly short order, and needing dozens of backplane slots.

This approach will also need multiple graphics controllers installed in the host (with multiple keyboards connected) and that just isn't the expansion or the software available with any of the OS X boxes.

Local graphics displays are very fast because they're local they're physically short I/O buses, and more expensive. Now if you want to have those gonzo-resolution displays directly driven from a central server - the core of the design used on various classic client-server computers, but with substantially upgraded graphics displays - then those designs don't work very well over the network, and for several reasons not the least of which are available bandwidth and latency acceptable to the users. If the remote clients are more capable (which is less common with 'mainframe' solutions', then you can also use Microsoft Terminal Services-style parallel logins on Lion and later, with remote OS X systems via Screen Sharing via ARD or with decent VNC-capable clients. That'd require installing and configuring XQuartz. You could probably also use ssh port forwarding and X (or straight X over IP) and get remote X11 displays on the clients. Multiple thin clients will also work here, too.) I regularly have multiple sessions open into various OS X clients and OS X Server boxes. (In the OS X case, it'll probably be a DEC VT terminal emulation and probably not an IBM 3270 emuation, and the VT emulation works very well for character cell operations these days. With a classic mainframe-style design, you can certainly telnet or ssh into the OS X Server box from thin clients or other such devices, and you can get something that's fairly close to an IBM 3270 green screen terminal display or a tn3270 emulation one of the displays that was common on classic mainframes.

Mainframe emulator for mac