Testing procedures
This page runs through the tests I conduct on a newly assembled and flash board to verify all functions are working. Testing is manually done as this is a likely low-quantity device with no need for elaborate automated testing.
Testing is conducted in 2 phases
- Standalone with test pattern
- Connected inside a PC to an ISA motherboard
Power is supplied from programmer module or 5V power source to pin headers.
I used a USB breakout board to power the board with 5V although you can power it up from the programmer module as well.
The board generates a test pattern on all interfaces, HDMI, VGA and composite when it is first powered on. Only when it is commanded from the host PC will the display change to what is required.
I go through all modes and check the outputs using displays connected to all 3. Using a different bitstream (using switches 3 and 4) will require a power cycle to the board or board reset using iceprog -t. Changing the display configuration (using switches 1 and 2) can be done on-the-fly.
Place the switches in this mode then power cycle/on the board
| 1 | 2 | 3 | 4 | Function |
|---|---|---|---|---|
| open | open | open | open | MDA 70Hz green |
MDA mode only outputs to HDMI and VGA, composite is not available.
Connecting a screen to the HDMI port, you should see something like the following with some characters blinking:
| 1 | 2 | MDA colour |
|---|---|---|
| open | open | Green |
| open | closed | Yellow |
| closed | open | White |
| closed | closed | Red |
Now cycle through the 4 colours on-the-fly to verify that they display similar to what is shown below. The characters shown need not match exactly.
Connect to a VGA monitor and you should see the following.
Only orange colour is available and switches 1 and 2 have no effect.
The test procedures for the 3 CGA modes are very similar hence I shall combine them all in this section and only mention the differences. Place the switches in your desired mode then power cycle or reset the board.
| 1 | 2 | 3 | 4 | Function |
|---|---|---|---|---|
| open | open | open | closed | CGA 70Hz, VGA mode, normal font |
| open | open | closed | open | CGA 60Hz, VGA mode, normal font |
| open | open | closed | closed | CGA 60Hz overscan, VGA mode, normal font |
HDMI is always active on all modes. VGA and Composite is determined by the status of Switch 1.
Connecting a screen to the HDMI port, you should see something like the following with some characters blinking:
On some monitors, you can show the specifications of the displayed signal.
Above shows what to expect in the 3 CGA modes under normal font. I'm using my Dell P1917S and it can display the specification of the received signal.
- CGA 70Hz: 640 x 400 x 71Hz
- CGA 60Hz: 640 x 400 x 60Hz
- CGA 60Hz overscan: 704 x 416 x 60Hz with black bars on the right and bottom.
To test thin font, change switch 2 to closed with no changes to resolution and refresh rate.
The fonts now appear thinner.
Maintaining the same switch settings as above, connect the VGA cable to a monitor. All the VGA output should look similar. Your monitor may align the display area to either the centre or top left.
Thick font.
Turn Switch 2 closed to enable thin font.
Connect a Composite cable from the board to a monitor. The CGA 60Hz modes should show the same result as overscan only works for HDMI. CGA 70Hz mode will not display anything.
| 1 | 2 | 3 | 4 | Function |
|---|---|---|---|---|
| closed | open | open | closed | CGA 70Hz, invalid composite mode, normal font |
| closed | open | closed | open | CGA 60Hz, composite mode, normal font |
| closed | open | closed | closed | CGA 60Hz overscan, composite mode, normal font |
Thick font
Turn Switch 2 closed to enable thin font. Thin font is indistinguishable from thick font in composite.
For a truly complete test, the board should be placed into a vintage PC with an ISA slot. The existing graphics card need to be removed to avoid confusing the BIOS.
Then repeat the above tests again.
Your system BIOS may need to be adjusted to display in Monochrome mode.
In this photo, the card is placed onto a 486 motherboard. The 4 different colours are cycled through in HDMI.
VGA will be displayed as amber.
Here the card is in my IBM 5155. The software CGA Compatibility Tester can be used to verify the card function such as colour palette. Do not expect all tests to pass as the implementation is not entirely perfect.