Which CPUs fit the ASUS X99-Deluxe?

It uses the LGA 2011-v3 socket and Intel X99 chipset, so it takes Haswell-E and Broadwell-E processors such as the Core i7-5820K, 5930K, 5960X and 6800K series. It does not fit newer Intel sockets.

How much memory can it take?

There are eight DDR4 slots supporting quad-channel memory, with speeds up to 3200 MHz when overclocked. That allows very high capacities for rendering, virtual machines or large datasets.

Does it support multiple graphics cards?

Yes. The board has several PCIe x16 slots plus x1 slots, so multi-GPU setups are possible with supported X99 CPUs. Check the lane-sharing rules in the manual before installing three or four cards.

Is it a good choice for a new build today?

Only if you already own an LGA 2011-v3 CPU or find the platform worthwhile for a workstation. It lacks USB-C, PCIe 4.0 and modern M.2, so a current board is a better base for a new general-purpose PC.

What form factor and case does it need?

It is a standard ATX board, so it fits ATX cases and many larger micro-ATX cases. Allow clearance for a large CPU cooler and long graphics cards.

Does it have built-in Wi-Fi and sound?

Integrated audio is included. Wireless networking varies by revision, so check the specific board's rear I/O for Wi-Fi; wired LAN and HDMI are present.