First things first: only comment here with firsthand evidence in a short and concise manner. Don’t speculate or ask if a motherboard will or will not have this problem. If you made any progress, send a PM, the post will be updated.

Preamble: this thread is to collect scattered anecdote of a problem collectively known as "VIA 0 bytes AGP memory bug" or "VIA AGP GART bug". It is relevant if:

1. You are running 98 / ME.
2. You are using a VIA chipset motherboard from mid-00’s.
3. You are using an AGP card. Both NVidia and ATi are known to have this.

The bug manifests itself in low 3D performance and was introduced with BIOS updates at some point in year 2004. As of writing it cannot be solved definitively by altering BIOS settings or downgrading a driver.

How to check:
Open 3Dmark2001SE system info window, and look for “Total AGP memory” value. If it is 0 bytes you got the bug.

Example on VIA PT880

Known half-solutions:

1. Downgrading BIOS (some motherboards).
2. Cross-flashing BIOS (some motherboards).
3. Running XP.
4. Using ForceWare versions from 61.76 and newer as they have a partial workaround.
5. Just use non- VIA-based motherboard

Confirmed affected motherboards:

• AMD:
  • Asus K8V-MX. Sighting: (Joseph_Joestar)
  • Asus K8V-X SE. Sighting: (bloodem)
  • Asus K8V SE Deluxe. Sighting: (Repo Man11)
  • MSI K8T Neo-V. Sighting: (adi88, AlexZ)
• Intel:
  • ASRock 4CoreDual-SATA2. Sighting: (Feamane, VDNKh, havli)
  • ASRock 775Dual-VSTA. Sighting: (Bruno128)
  • ASRock P4V88. Sighting: (Bruno128)
  • Asus P4V8X-X. Sighting: (deksar)

Further reading:

• Researching the AGP target registers (VDNKh)

P.S. If this piece of puzzle is ever solved, it is a step ahead in terms of pushing the limits with Win98 builds. Thanks for cooperating!