ISA Super VGA

Overview

The ISA Super VGA card is based on the Trident TVGA9000i Super VGA controller IC. It offers excellent compatibility with the original IBM VGA, as well as a good emulation of older CGA, EGA, Hercules and MDA adapters. The ISA Super VGA card was designed to be used with the Xi 8088 Processor Board, but it also works in IBM PC/XT and their clones. It will work in 16-bit ISA slots of AT-compatible computers, but its performance will be inferior to 16-bit VGA cards.

Note: PCB Version 1.0 requires a rework for compatibility with the original IBM PC and IBM XT computers, please see the Errata section below. This errata was fixed in the PCB Version 1.1

Picture

Specifications

• • Supports 256 KiB or 512 KiB video memory using two or four 256 Kbit x 4 DRAM ICs.

  • 8088-friendly VGA BIOS.

  • Only 6 ICs (SVGA IC, BIOS, four DRAM chips), some capacitors, resistors and inductors.

Bill of Materials

Changes

Version 1.1

• Fix ALE errata. ALE signal is now connected to 5V

• Slightly move VGA DE-9F connector (about 1.27 mm up and 0.8 mm back) to better comply with ISA card size and bracket placement specifications

Version 1.0

• Minor board modifications around JP1

Errata

Version 1.0

• The original IBM PC, the original IBM XT, and XT clones that closely follow IBM XT schematic do not implement the ALE signal properly. In these computers the ALE signal occasionally activated during DMA cycles, for example during memory refresh, while the address on the address bus is invalid. This confuses the Trident TVGA controller. The following rework is required to make ISA Super VGA work in these computers: The TVGA9000 ALE signal needs to be disconnected from the ISA ALE signal, and connected to the 5V power signal. The photo below shows such modification (photo credit: keropi at VCF forum).