id = 2920
title = "VGA Passthrough I/O Lag on DOS (FreeDOS) System."
state = "closed"
created_at = "2025-04-12T07:37:11.825Z"
closed_at = "2025-04-25T12:34:09.224Z"
labels = ["VFIO"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/2920"
host-os = "Void Linux"
host-arch = "x86_64"
qemu-version = "QEMU emulator version 9.2.93 (v10.0.0-rc3)"
guest-os = "FreeDOS"
guest-arch = "x86"
description = """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."""
reproduce = """1. Install Doom (v1.9 Shareware.)
2. Run setup and disable sound.
3. Play game or watch demo."""
additional = """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])**"""