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Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-10, 14:21

The EGA BIOS really reads the dipswitches, but practically inverses the bits in the result from the bits in the MISC OUTPUT REGISTER outputs to read it. So clock #0 returns bit #3, clock #1 returns bit #2, clock #2 returns bit #1 and clock #3 returns bit #0 as stored there. So the bits are stored …

Re: The 8088 Prefetch Algorithm

Posted on 2024-02-10, 02:35

What's better than a simple model? An even simpler one! State transitions? Get those out of here! What if absolutely every bus "delay" on the 8088 was simply explained by a 7 cycle bus access time? https://martypc.blogspot.com/2024/02/the-comp … intel-8088.html

Re: 8088 assembly help

Posted on 2024-02-09, 22:20

Even on 8088 its best to use word versus byte if you can, as it saves instruction decode time by just doing half as many (obviously the 8088 can only load/store 8 bits at a time but every saving is worth it). Not to nitpick, but rep movsb is only decoded once (assuming no interrupts occur). The REP …

Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-04, 20:14

C0-C3 are of course first masked by Color plane enable before any other processing into an index into the LUT. Right. The color plane enable basically masks the address bits to the attribute palette registers. The documentation mentions it uses C2 and C0 and their combination effects when MONO ( …

Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-04, 17:41

Anticipating a followup question - what tells the attribute controller to draw 9 columns? It looks like the S/L is edge-triggered. So that's the attribute controller's signal to start serializing its character and attribute input lines. I assume if doesn't receive another S/L transition that on the …

Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-04, 16:50

OK. So the attribute controller gets the 8 pixel on/off states if text mode in parallel and shifts it out itself during each pixel clock? Each dot clock, specifically. The dot clock input is provided by the sequencer, and we can set the dot clock to divide the pixel clock by 2 - this is how we get …

Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-04, 16:17

Some of the memory address generation may be confusing. You'll only see 8 address bus lines at any time - how do we address 64k per plane with 8 bits? The key is that the DRAM chips use row/column addressing. They have have 8 row address bits and 6 column address bits. I find it easier to flip rows/ …

Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-04, 15:45

But unlike those lower 4 bits, the upper are always driven by the MID inputs? What are those MID inputs? M1D is the attribute byte. It's an entire byte - 3-4 bits for foreground color and 3-4 bits for background color, but as we have seen the 3rd and 7th bit gets borrowed for other purposes, …

Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-04, 13:42

I see attribute 0-3 coming from a chip that has inputs C0/MID0, C1/MID1 from sheet 6(graphics controller), but C2/C3 from sheet 7 and MID2/MID3 from sheet 6(which is the graphics controller)? sheet 6 says (graphics controller) C0/C1 outputs to C2,C3(sheet 8 )??? Perhaps the chain logic? Don't get …

Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-04, 13:16

The odd thing about this case is you mention bit 3 to indicate blinking. But bitplane 3 is masked off always with 64K VRAM on the EGA? I am not sure where you came to this conclusion. Two points: All bitplanes are available on the 64KB EGA, just each has 16K Bits in the text attribute are not …

Re: EGA/VGA and mode Fh mono 'colors'?

Posted on 2024-02-04, 00:56

Is that blinking applied to the data gotten from the sequencer (4 planes) or to the attribute controller output (what's in the registers)? Rn it's the former in UniPCemu's emulation. But does that apply with the register sets I mentioned in the first post (planes 0 and 2 being enabled only for …

Re: MartyPC

Posted on 2024-02-03, 17:27

Thanks for the update! How important is being able to format a floppy in an emulator? I suppose I could let you select drive size along the lines of "360k", "720k", "auto" and auto would just behave how it does now. Well, some games want to format a floppy when being installed. I have "Balance of …

Re: MartyPC

Posted on 2024-02-03, 16:55

So it's February 2024, where the hell is 0.2? I'm getting there - still tackling some intransigent bugs, issues with frame pacing, sound and other issues. Another minor rework to the CPU and a major bugfix in the PIC fixed several titles where segment address wrapping occurred, improvements to the …

Re: MartyPC

Posted on 2024-02-03, 16:29

Sorry for the late reply - somehow I did not get a notice. It is any of "PC booter" games by Infocom - they all require the disk to be write-protected. Like "The Hitchhiker's Guide to the Galaxy", "Cutthroats", "Zork" etc. Okay, was able to reproduce and happy to report the new write-protect …

Re: how to setup italian keyboard on ms-dos 3.30

Posted on 2024-02-03, 01:11

Some old MS-DOS (I remember it from an Amstrad PC-1512 floppies, but that was MS-DOS 3.20) does NOT have the keyb comand. They have a keyb xx command for every language supported. So it would be keybuk (UK keyboard), keybsp (spanish), keybit (italian)... That's fine, but the version of DOS was …

Re: how to setup italian keyboard on ms-dos 3.30

Posted on 2024-02-01, 15:11

FIN_K89i wrote on 2024-02-01, 14:35: ye i know but where i can ask? also the command didnt work Please learn how to be helped - don't just say something "didn't work" - explain: was there an error message? did it return the dos prompt but appear to do nothing? what happened when you ran it?

Re: MartyPC

Posted on 2024-01-27, 02:59

Another question for the long run: is it possible to configure GLaBIOS somehow to skip the RAM check. I reboot MartyPC quit often, and waiting for the RAM check is boring :). if we had a fixed RAM config maybe, but GLaBIOS needs to determine the memory size, and that's now configurable in MartyPC. …

Re: PCEM vs 86Box vs UniPCEM vs DosBox-X

Posted on 2024-01-22, 14:36

UniPCemu came from 'Univeral PC emulator', as the main thought behind it was a PC emulator that's cross-platform and easier usable on gaming consoles etc. (Starting off on the Sony PSP after all, because Dosbox was difficult to control with such inputs and not accurate enough to my tastes). I saw …

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