Software:demoscene:Chain 4 by The Silents (1992)

1992 demoscene entry.

Demo description

Basic 3D object demo with music. It uses a flawed VGA unchained ``mode X'' implementation.

Recommended DOSBox-X configuration

[dosbox]
machine=svga_et4000
memsize=1

[cpu]
cycles=12000
core=normal
cputype=386

[sblaster]
sbtype=sbpro2
sbbase=220
dma=1
irq=7

Demo uses VGA unchained ``http://en.wikipedia.org/wiki/Mode_X[Mode X]'' but forgets to program the byte/word/dword mode of the CRTC for the Mode X rendering to display, which will cause it to misrender if VGA emulation other than Tseng ET4000 is used. Mode X appears to be used for fast polygon filling and page flipping. Sound Blaster support assumes IRQ 7, demo will not produce sound otherwise.

[[images/Demoscene:Chain-4-by-The-Silents-(1992)-et4000-vs-vga.png]]

A cycles count between 5000 and 12000 is recommended to avoid flickering and visible redraw. If the cycles count is too high, the audio clip played during the opening logo may skip over the first 1-2 seconds.

Further testing

I would like to run this demo on actual hardware to see if it has problems on non-ET4000 SVGA cards in the same way that it fails to work under DOSBox.

Test results

I have tested the demo on the following hardware so far. OK'' means the demo renders correctly (as shown in machine=svga_et4000 screenshot). Failed'' means the demo rendered incorrectly (as shown in machine=vgaonly screenshot) where for every group of 16 pixels the first 4 are read. Result field will contain more descriptive text in the event anything else happens.

Mfg.	Card/Hardware	Result
Chips & Tech	CT65550	Failed
Chips & Tech	CT65554	Failed
Cirrus Labs	CL-GD7543	Failed

More information

More information (Pouet)