crazyc has just updated his PSP DosBox DOS emulator.  Here's what he said:

crazyc Wrote:New patch and binary.  Fixed the audio somewhat and switched to the scummvm ym3182 emulator.  Also, made the x87 use single floats instead of double, this will probably cause problems with some apps, but should be a lot faster with programs that use the fpu frequently.  The 16 color vga modes now use 4bpp textures, not much of a speed improvement here though because converting the data from planer to packed is cpu intensive; if any has any ideas how to speed this up, right now it uses a lookup table , I'd like to hear them.

- Source: [PS2Dev forums]

Certainly interesting, especially for those wanting to play some old DOS games on the PSP :P