In the mid-90s Intel introduced the Advanced Technology eXtended (ATX) specification for motherboards which still applies to desktop computers to this day. ATX is an evolution of the AT form factor and in fact the specifications share some common motherboard mount positions (ATX is a baby-AT motherboard rotated 90 degrees in the PC case). ATX specification also applies to power supplies and the type of connector that interfaces a power supply to a motherboard.
The original ATX motherboard format (sometimes called "full size ATX" or "standard ATX") dictates a motherboard size of 305x244mm with mount points that would apply to all smaller motherboard iterations since.
The microATX spec arrived in the late 90s and in 2009 Mini-ITX was introduced - again all using mount points within the original ATX specification and, while height restrictions inside the case varied, the IO connector zone remained in the same position and size. The I/O connector zone being that panel of connectors at the rear of a PC where you plug things like monitors, keyboards etc into.
This means ATLANTIS for MiSTer, which follows the Mini-ITX specification, should also fit inside most microATX and standard ATX cases along with any other ATX variants and even AT (albeit just off two mount points but potentially supported by spacers/standoffs on the other two free mount holes).
The question then becomes;
How high can my MiSTer stack be and still fit inside a Mini-ITX/ATX case?
The limiting factor across all of these cases is generally not the height of the case itself but the IO connector area dimension, which as stated is the same specification across ATX, microATX and Mini-ITX (except Thin Mini-ITX but I'll get to that shortly) at ~158x44mm. Slight differences in clearance allowance can make this cut out smaller or larger across manufacturers but generally this is what we have to work with.
And in general, you will be able to fit a "triple stack", ie USB hub, DE10-Nano, analog IO with VGA connector sandwich, through this IO area. In some cases you will be able to mount your triple stack on top of the ATLANTIS and have all connectors accessible, in other cases the VGA connector may be too tight along the upper edge of the case. In this circumstance the USB hub can be mounted from underneath the ATLANTIS, sinking the MiSTer stack a few millimeters and providing clearance for the VGA connector. Or alternatively you can mount the USB hub side by side with the MiSTer.
What is Thin Mini-ITX and how does it compare to Mini-ITX?
About a year after Intel released the spec for Mini-ITX they introduced an addendum with a subcategory of Mini-ITX called "Thin Mini-ITX". The significant feature being the reduction in height of the IO connector area down to a mere 25mm (from 44mm) and along with it, reductions in height zones across the motherboard. These cases can be tiny! Some not much more than 30mm thick.
In this scenario a single DE10-Nano with vertical RAM (as is common for most MiSTer setups) will fit inside a 36mm height case but again can be mounted from the underside of the ATLANTIS to gain a few millimeters extra clearance if required - just be careful not to have it too low and NEVER have it touching the case itself!
(Always be conscious of avoiding contact between any part of your MiSTer system and the PC case - shorts can kill electrical devices)
Can you fit a stack of say a DE10-Nano and analog IO board in such a Thin Mini-ITX case?
The answer is... maybe.
From the base of the HDMI connector to the upper edge of the VGA connector is approximately 24.75mm - it will likely just squeeze through most Thin MIni-ITX IO areas BUT having the VGA connector touching the upper rim could impede fully engaging a VGA cable and most probably require some modification to the case for practical use.
Til next time,
Experiment, have fun and let everyone know what you find works or doesn't.