WHT Turbo Video for Myarc Geneve 9640
The WHT (Western Horizon Technologies) Turbo Video Mod is a hardware-based performance upgrade for the Myarc Geneve 9640. Its primary purpose is to accelerate video data throughput by optimizing how the CPU interacts with the Video Display Processor (VDP).
1. Performance Increase
20% Speed Boost: On average, the mod provides a 20% increase in video performance. The exact improvement varies depending on the graphics mode being used and the intensity of the video writes.
Wait State Reduction: The mod works by replacing the standard programmable logic (PAL) chip at position U202 with a custom-coded version (often a GAL or PAL). This new logic reduces or removes the wait states that the Geneve's hardware typically imposes during video operations, allowing the TMS9995 CPU to send data to the VDP more efficiently.
2. Enhanced Compatibility with GenMOD
While originally designed for standard Geneves, the mod was eventually "dialed in" to work with GenMOD-upgraded units.
Early versions of the turbo chip removed too many wait states, causing stability issues on faster GenMOD systems. Later revisions balanced this to ensure the system remained stable while still providing the speed benefit.
3. Hardware Requirements & Constraints
Installation: It is a "drop-in" replacement for the U202 PAL IC with a replacement GAL IC provided your U202 is socketed. If it is not socketed, then your board will require someone to remove the chip and replace with a socket.
Board Revision Sensitivity: Not all Geneve 9640 boards are compatible. Some first-generation cards (Revision A or very early production) may not handle the reduced wait states correctly, leading to "sparkles" on the screen or system crashes.
VDP Requirement: While it works with the standard V9938, it is most effective in systems where the video bus is not already bottlenecked by other slow components.
- Model: WHT_TURBO_VIDEO