I guess the simplistic question was too simplistic! Let me give more detail on why this is important.
Users and 32bits
I run some apps that require 32bit windows. I could port them over to 64bit but it would require un-necessary work because the roadmap for the development is to go all Linux.
One reason for this is because from next year Microsoft are going to start dropping support for Skylakes on Windows 7, 8 and 8.1. They will only produce the most important security updates for those products and the intention here is to "get 1 billion users of Windows 10". Note too that future processors (Kaby Lake) will only have support for Windows 10. If you think faffing around with installing windows 7/8 on a Skylake rig is a bit of a bind now wait until you try it on Kaby Lake - it may not be possible at all.
One other point on 32bits. There are probably thousands of users that do require 32bits but you will never know about. Medical research, finance, meteorological, all kinds of research are probably still using it.
Why? Because it is faster
for their setups. I totally appreciate you can have more memory, things move in 64 bits instead of 32 and that games could be faster. But remember there are thousands out there that have 32bit running faster than 64bit and they won't shift.
Motherboard Manufacturers and 32bits
If no one is using 32bits on Z170 then why do manufacturers offer drivers for 32bits?
I go on the Gigabyte site
http://www.gigabyte.com/products/product-page.aspx?pid=5496#dl
I click Support and Downloads, choose Drivers, I am then offered a selection of:
* Windows 7 32bit
* Windows 7 64bit
* Windows 8 32bit
* Windows 8 64bit
* Windows 10 32bit
* Windows 10 64bit
If Z170 'is not compatible with 32bits' then why are they offering drivers for it?
The Issue
I have a Z170-XP-SLI. No matter how I configure this (4GB, 8GB, 16GB), Windows 7, 8, 8.1 (32bit) the O/S is reserving 1.9GB.
Now don't jump in there saying "errr 32bit windows only allows 3.25GB - 3.5GB free). I know that. I have known that since the 90s. Everyone knows that.
The issue is that this motherboard is reserving 1.9GB rather than 0.5GB - 0.75GB, which every other rig I have ever had since the start of the millennium.
Let me just repeat. This is not the usual Hardware Reserved of around half a gig, but The Z170 is forcing windows to reserve half a gig + another 1.25GB for some reason.
Resolve It
I can't. I have tried everything and I mean everything. There is nothing else left to try.
This is why I need to find out if this extra 1.25GB of missing RAM is happening to other manufacturers or other Gigabyte boards.
I want to log a ticket with Gigabyte but to prevent them from batting it back I need evidence that this either happens with other boards (that have a specific condition) or if it ony happens with Gigabyte, or if it only happens with the XP-SLI.
My assumption is that this is a simple BIOS setting. I am going on the angle that something like the > 4GB switch is missing from the XP-SLI BIOS and that Gigabyte need to add it.
Or it could be that this board is faulty and needs RMA'ing.
But I can not prove any of this unless I get some test data from other boards