VGA Passthrough I/O Lag on DOS (FreeDOS) System.
Description of problem:
VGA performance lags with passthrough when the OS is in graphics mode. It also seems to affect when key presses are registered with noticeable delay.
Steps to reproduce:
1. Install Doom (v1.9 Shareware.)
2. Run setup and disable sound.
3. Play game or watch demo.
Additional information:
I have tried multiple cards with no change in performance:

**VGA compatible controller: S3 Graphics Ltd. 86c375 [ViRGE/DX] or 86c385 [ViRGE/GX] (rev 01) (prog-if 00 [VGA controller])   
VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] R480 [Radeon X800 GTO] (prog-if 00 [VGA controller])**