DOSBox 15kHz/240p tips

[bjt42]

Not Groovymame related I know, but thought this might be useful for someone.

Spent a while playing around with various versions of DOSBox. DOSBox 0.74-3 (latest stable) seemed to work the best, the forked versions with VSync & Direct3D exhibited various issues.
My objective was to get pixel-perfect, unfiltered output with as smooth scrolling as possible and no tearing. Output at 320x240 @ 60Hz to a 15KHz display using CRTEmudriver on ATI 5450 under Win 7 Embedded.

fullscreen = false # prevents freeze on startup
fulldouble = true # needed to prevent tearing
fullresolution = original # selects 320x240
output = ddraw
machine = svga_s3
aspect = false
scaler = none
cycles = fixed 40000 # needed as max mode causes slowdown

I use multimonitortool to select 320x240 mode before starting DOSBox, and change back to 640x480 interlaced after DOSBox quits.
For some reason, setting fullscreen = true causes DOSBox to freeze on startup. For this reason I start DOSBox in windowed mode, then send ALT-ENTER after 5 seconds to select fullscreen mode. I use an AutoHotKey script for this.

It works surprisingly well, albeit with letterboxing as most DOS games are only 200 high. CGA and EGA games run completely smooth (as they were 60Hz refresh originally), 320x240 VGA mode X is smooth too. VGA 320x200 games have the odd small stutter, as they are 70Hz.

[psakhis]

Hi, i think PCEM it's better for real dos emulation and vsync works better than DOSBOX.

I have configured with all resolutions (320x200, 320x240, or 640x680i) depending on the game with no problems.