First post, by superfury
On a real ET3000 SVGA, does setting the 8 simultaneous fonts have effect on the attribute controller?
Can the attribute controller disable the background plane bits (bits 4-7 of the attribute sent by the graphics controller) with this enabled (to make it black or something like that)?
Reading Advanced Programmers Guide to SuperVGAs by George Stutty and Steve Blair, at page 422, the enable bit is described in the TS index 07 bit 4 being set(Enable Multiple Soft Font). It's apparently protected by Vertical Sync End bit 7 like CRTC0-7.
Attribute bits 3,4,6 are apparently mapped to font bits 0,1,2 respectively? Bit 5 is bit 6(F2) complement?
The offsets are then, apparently:
0K,16K,32K,48K,8K,24K,40K,56K
So it's 8K offsets? So that's memory address bit 13 (MA13-MA15) being driven?
And bit 2 clearly drives MA13.
And bit 0 clearly drives MA14 and bit 1 drives MA15, seeing the increments in 16K units.
The example also clears the character set A/B register, writing 0403h to sequencer index/data registers (word operation). And attr 12h to 07h (3 planes only) for some reason? Why would it do that? Does it have to do with the background bits?
For now I've followed the documentation I found and clear bits 3-6 of the attribute controller inputs (bit 7 is left for blink support, documented masked off if enabled).
The background has now changed to black:
See Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i) for more information on the previous state without clearing those bits for the attribute controller.
Author of the UniPCemu emulator.
UniPCemu Git repository
UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io