New PC build: Asrock N100DC

I decided that I was setting a bad example by running my own lathe on LinuxCNC 2.8.0~pre on Debian Wheezy. So I installed the latest LinuxCNC ISO on the DN2800MT that I built it with in 2015.
This consumed the entire 8GB SATA DOM SSD and was glacially slow. LinuxCNC and latency was fine, but UI response horrible, and I was having to press the cycle-start and (more worryingly) cycle stop buttons for a couple of seconds to get a response. Possibly a graphics issue, as Linux has never properly supported that chipset. It's also debatable whether it's a fully 64-but motherboard. (The specs and manual simply don't say...)

I could try playing about with graphics drivers and such. In fact I did, a bit, but then I got bored and bought a new motherboard. 

Asrock N100DC  www.mini-itx.com/~N100DC-ITX
The shopping list was:
PCIe slot (for the existing Mesa 6i25)
DC Power input ( to run off the controller 12V)
M2 SSD slot (so that there is no need to sort out SSD brackets, and to keep everything compact and low-power)
VGA connector (but it also has HDMI) so that my existing touchscreen (and touchscreen wiring, through the conduits and machine base) will work

Other possible plus points:
It has a parallel port header on the motherboard, in case you want to go old-school
It has a serial port, and a motherboard UART port too. 

Latency is "fine". It runs at 11k most of the time, but can go up to 25k when opening web browsers, GLX gears, that sort of thing. Perfectly OK for a Mesa card. This is with an un-tweaked LinuxCNC 2.9.3 ISO install. 

It's very snappy (possibly the SSD?) Touchy opens in under 2 seconds from pressing the button, and its 30 seconds from power-on to a responsive LinuxCNC GUI once autologin and autostart are set up. (and several seconds of that startup are spent waiting for grub to timeout and load the default). 

I added an 8GB DIMM (the smallest DDR4 I could find) and a 240GB M2 SSD (again, the smallest and cheapest I could find)
Motherboard £106 + VAT
Memory      £12.99
SSD           £16.29
Total   =     £156

More than a Pi, but it will slot right in to the existing space. 

In case anyone was excited by the motherboard UART header, apparently it's only accessible by the BIOS during boot, and is not available to the OS.

It's hard to say without testing. There may be improvements to be made with isolcpus and other tweaks too.
If the board you get matches the one have with 25k latency then you should be able to step at about 5kHz (theoretical is max is 40kHz with a 25k base thread, but the differences in motor speed between every 5th cycle and every 4th and so on are more than the motor will follow)
With 4x microstepping 5kHz is about 375rpm at the motor shaft. Or 1800mm/min with a 5mm pitch screw..
You might want to start with software stepping / parport to get going, but it's not the best solution. If you are using a paralle port already then a Mesa 7i90 can be used to massively increase step rate and smoothness, and it adds a lot more IO too. There are other options from Mesa too, as well as from Pico systems and you can also look at the alternative firmwares like Remora for alternative hardware.

I think that's about as good as it gets, and it's perfectly usable for most purposes (especially if you don't plan on using software step generation or encoder counting)