For those who just want the fix and to skip the commentary, go here.

Paint.NET v3.5.x requires a CPU with SSE support. Since SSE is a 10-year old technology, it was a pretty safe bet. I have only received one e-mail from a user who was confused about this. Oh, and a single blog comment from a gentleman who apparently believes he’ll be using the computer he bought in 2001 for a total of 20 years. That certainly is a long time to stick with XP! More power to him, but I certainly won’t be supporting XP anymore in the year 2020. Anyway …

The reason that SSE is required is for three reasons, none of which are really good enough on their own but together they were acceptable:

  1. DDS (DirectDraw Surface) file type support makes use of a C++ library called “Squish”. It has 3* optimization levels that can be chosen at compile time: normal, SSE, and SSE2. Enabling SSE for 32-bit systems was shown to yield a very large performance improvement. For 64-bit systems, enabling SSE2 is a no-brainer because all x64 CPUs support it.
  2. I wanted to cut down on the number of native DLLs that I had to dispatch out to, which would reduce the surface area of code that I was liable to maintain. Put simply: fewer code configurations means fewer bugs. In Paint.NET v3.36, I had 3 versions of Squish: x86, x86_SSE2, and x64. I knew that going forward this would turn into a rat’s nest of spaghetti code as I added more functionality to the “native” DLLs. Thus, I eliminated x86_SSE2 and switched on SSE “1” for the x86 DLL. There was also some additional native code consolidation. Almost all CPUs nowadays have SSE support, so this didn’t alienate very much of the user base.
  3. Eventually I will move Paint.NET to require SSE2, for reasons I will discuss later. Requiring SSE is a step in that direction.

Anyway, all this discussion aside, I just discovered that I accidentally compiled Squish to use SSE2. Oops ! The consequence is that if you have a Pentium III or Athlon XP and try to save a DDS file, Paint.NET will just crash, silently close, or print “Error” in the Save Configuration dialog.

You can wait for the next update, Paint.NET v3.5.3, or you can make use of the patch that I’ve published on the forum.

* Actually it has 4, because it also supports AltiVec. However, that’s for PowerPCs, and so doesn’t matter for Paint.NET.