CPU

ARM
    32-bit: most ARMv7 CPU implementations
    64-bit: any ARMv8 CPU implementation

PowerPC
    32-bit: 7xx family or newer (e.g. G3/G4)
    64-bit: 970 family or newer, tuned for POWER8/POWER9

Intel x86
    32-bit: Pentium-class w/ MMX (e.g. Intel P55C, AMD K5)
    64-bit: any Intel or AMD CPU with 64-bit extensions

Minimum: 100 MHz for Server, 600 MHz for Desktop
Recommended: 800 MHz for Server, 1200 MHz for Desktop

RAM

Minimum
    Server: 64 MB
    Desktop: 384 MB

Recommended
    Server: 128 MB
    Desktop: 1 GB

This will vary widely by workload and should be used as a baseline only.

Disk

Minimum
    Server: 350 MB
    Desktop: 6 GB

Recommended
    Server: 500 MB
    Desktop: 10 GB

This will vary widely by workload and should be used as a baseline only.

Graphics

Minimum
    Server: (none)
    Desktop: 4MB VGA capable of 800x600 resolution

Recommended
    Server: basic VGA
    Desktop: 128MB VGA capable of 1024x768 resolution

Network

Optional (for updates).