Construction Information

The most up-to-date board revision as of 5/29/2017 is 1.0-003. The Bill-Of-Materials below reflects a number of chip substitutions:

  1. Two of the 74LS244's are updated to 74ACT244 logic; one is unchanged
  2. Two of the 74LS374's are updated to 74ACT374 logic
  3. C1, 22uf on the schematic, is updated to 100uf or larger.
  4. Two 10uf Tantalum capacitors are substituted at C9 and C11.

The GAL chips are both ATF16V8BQL-15PU. The 15ns speed is important. Slower and faster GALs have led to unreliable operation. The -BQL suffix is the lowest power version.

Layout Indicating updates:

Construction Files

ECB-VGA3-BOM.png 191kb26-May-2017
ECB-VGA3-BOM.ods 20kb26-May-2017 2.6kb07-May-2017 0.6mb12-Apr-2017


The Programmers' Reference Manual is primarily for system programming at the BIOS level. Direct memory-mapped updating of display memory operates in a fashion identical to that of the IBM MDA/CGA/EGA/VGA adapters.

The schematic does not reflect the component substitutions specified in the BOM. Several components require update to faster versions.

VGA3-Programmers' Reference 1.1 333kb15-May-2017
VGA3 Test Programs 355kb24-Jul-2017
VGA3 Schematic 1.0-003 493kb31-Jan-2015
HD6445 Datasheet 1023kb


The test program ZIP file contains a tarball of the source, which includes a number of font files. The ZAP fonts are used under the GPL 3.0 license.

v3mtst.comTest of onboard memory.
v3tpat.com80×25 screen alignment pattern - jumpers HSYNC=neg, VSYNC=pos
v3tpat2.com80×30 screen alignment pattern - jumpers HSYNC=neg, VSYNC=neg
v3tpat3.com80×25 70hz screen alignment pattern - jumpers HSYNC=neg, VSYNC=pos. Escape to exit.
v3tpat4.com80×30 60hz screen alignment pattern - jumpers HSYNC=neg, VSYNC=neg. Escape to exit.
v3tpat5.com80×43 screen alignment pattern - jumpers HSYNC=neg, VSYNC=neg. Escape to exit.
vga3tty.comDisplay keyboard scan codes through TTY interface. Reset to exit.
vga3kbd.comDisplay keyboard scan codes through hardware interface. Reset to exit.

Software configuration

Video output and keyboard input for the VGA3 board are supported in ROMWBW. It is included in the default build for the ECB-MK4 only.

To enable VGA3 board support in other ROMWBW builds, the following option should be enabled:


Screen formats supported are 80×25, 80×30 and 80×43, with 80×25 being the default. Display formats can be changed as follows:

boards/ecb/vga3/construction.txt · Last modified: 2020/01/10 07:01 by b1ackmai1er
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