While there are a bunch of older archs most are quite well and alive (hence supported by Debian). For example, there are a bunch of POWER8 machines in buildd, o

While there are a bunch of older archs most are quite well and alive (hence supported by Debian). For example, there are a bunch of POWER8 machines in buildd, or some fairly recent SPARC machines. Some of these machines are donated. FPGA emulation would be a huge project, both time/involvement wise and also cost-wise (FPGAs are freakin' expensive). Software emulation gets nowhere near usable performance, even with older archs (say PowerPC970) the real, >10 year old hardware is much much faster than any emulation, which also tend to be rather limited. For example, PPC in QEMU is actually not the 970 (G5), but an G3ish thing. Conversely, the virtual machine is limited to 1.5 GB of RAM (iirc). Technically you can build stuff on that. It just takes ages. 2-10 minutes for compiling a C module. The real deal (a G5 in the cellar) on the other hand can be stuffed with RAM to 8-16 GB and will be about as fast as a slow laptop nowadays is. (Except it will make much more heat and will be louder. Well, the latter depends on the laptop, hellish noises they make...).