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Re: EXCELGRAPH - ISA Video Display Controller

Posted on 47 minutes ago

OK. Just made a fix for the terminate/suspend to be loaded into the queue as a non-value write (behaving the same as a written value that doesn't process anything other than termination, but with the exception it's sort of side-loaded as an extra status to MMU register writes(so the MMU register …

Re: (S)VGA 256-color shift and Chain 4

Posted on Today, 04:18

But then why is it expecting to be in Chain 4 without Chain 4 being set? Edit: So then Shift 256 is OR'ed with Chain 4? That might be true but then wouldn't the Windows 95 boot screen and Wolfestein 3D both break since I have observed both of them using 256-color planar mode? Edit #2: Reading the …

Re: (S)VGA 256-color shift and Chain 4

Posted on 2021-04-08, 20:08

The OS/2 ET4000AX driver also writes to sequencer register 0E (which is entirely undocumented!), setting bit 1. The Windows 3.x ET3000AX driver sets bits 4 of attribute register 0x16. Edit: And I'm running the actual BIOS'es as well. What I see, with both of those drivers, is the card being put …

Re: (S)VGA 256-color shift and Chain 4

Posted on 2021-04-07, 16:32

It's indeed Tseng-specific behaviour. All other graphic card(including IBM VGA) just use the Sequencer Mode Control register bit. Tseng also doesn't call the GDC bit by it's normal name(256-color shift mode (loading for the latches when rendering)), but calls it linear graphics(LG) mode because it …

Re: Getting UniPCemu up and running

Posted on 2021-04-06, 11:51

Hi, I did some further testing on that "Linux x64/sse4.1 black screen bug" I mentioned earlier and found out that this bug is glibc-related: UniPCemu works just fine on the musl-based Void Linux, for example. Here's a workaround for glibc-based distros (needs glibc >= 2.26 I think). Add this env …

Re: VGA difference of blacks?

Posted on 2021-04-03, 10:49

I've already implemented said option for active display in UniPCemu's current commits. It also helps seeing where the active display is actually positioned on the screen, as you can see where the active display is starting and ending and where it's not outputting any pixel data (to see if output is …

Re: EXCELGRAPH - ISA Video Display Controller

Posted on 2021-03-30, 10:17

I have seen the memory range array in the ASM code as a string of DBs. Maybe the ROM BIOS image was made for ET4000AX as well? That one can handle 256K. Then again, at page 186 of the datasheet, the hardware memory addressing lines are described. And the minimum is 512K. I think the BIOS might be …

Re: EXCELGRAPH - ISA Video Display Controller

Posted on 2021-03-29, 14:52

It's still a bit weird that although 256K isn't supported by the chips the BIOS supports (cannot be detected or implemented on the W32 chip), it still is included in the lookup tables to the texts and of course the texts itself (It literally says "256KB", entry 0 in the list). Perhaps it's used for …

Re: EXCELGRAPH - ISA Video Display Controller

Posted on 2021-03-29, 14:29

That was a great read! And good thing you are now detecting the RAM correctly. Thank you for the analysis. Indeed 256K is not supported by the W32i variation. I did a quick search on the Internet and found out the following source code that targets the ET4000/W32i amongst other stuff. Maybe it is …

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