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Re: The Quest for Pixel Perfect DOS Emulation

Posted on 2021-06-22, 20:16

Well, UniPCemu renders it in it's entirety (everything but the retrace areas itself, so including overscan and active display, which Dosbox doesn't do afaik). After it renders it, it resizes the rendered screen to the specified resolution (usually in 4:3, although 4K and 1080p aspect ratio is also …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2021-06-19, 04:34

OK. The BIOS int 13h call seems to fail for the NT CD-ROM boot because it's using drive FFh, but it only allows hard drives up to 82h? So perhaps during the CD-ROM boot, FFh in DL is somehow incorrect (it's supposed to be 81h for the first CD-ROM drive?)? Edit: This is what happens during booting of …

What x86 exceptions always set EXT for their faults?

Posted on 2021-06-14, 06:21

What exceptions always set the EXT bit for all their faults on x86? I have all exceptions after a second layer fault set it (for example #GP(0) throws #GP(0) throws #GP(1), as long as it's not double faulting). Also, any instructions causing a fault themselves are counted as an interrupt cause ( …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2021-06-13, 23:04

OK. It (with the exception of the now working floppy-based part of setup) manages to get the GUI starting for the second part of setup. Then, the mouse cursor displays and operates properly, after which some HDD activity follows after which it resets the emulated system? So there's still something …

Re: Floppy disk write sector vs implied seek?

Posted on 2021-06-13, 20:52

So the drive, when ejecting a disk during a seek/read/write command, causes it to stop responding to the FDC until the next command starts (timing out any command pending for a read/write, both with and without implied seek)? What would be reported in ST0/1/2 in that case? Would that simply set the …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2021-06-13, 12:43

OK. After the latest improvements regarding the EXT bit in the protection fault handling (setting it automatically in some cases) and resetting the BIOS ROM and CMOS RAM (and reconfiguring it), Windows NT 4.0 workstation's floppy disk boot disk 2 seems to continue booting! At least it's getting to …

Re: Floppy disk write sector vs implied seek?

Posted on 2021-06-13, 12:12

If the disk is ejected during seeking, the seek would complete without issues (the drive's step motor is still going to move the head), but the read command is not going obtain any data from the drive, and therefore most likely time out, which would cause DOS to report "Not ready reading drive A:". …

Re: Floppy disk write sector vs implied seek?

Posted on 2021-06-12, 17:50

When does a write command perform implied seek? Before or after the data transfer to disk? Before. If implied seeks are enabled, when a READ SECTOR ID, READ TRACK, READ DATA, READ DELETED DATA, WRITE DATA, or WRITE DELETED DATA command is issued, the FDC compares the specified sector ID's cylinder …

Re: Floppy disk write sector vs implied seek?

Posted on 2021-06-11, 10:02

I just looked a bit further. In the 82077AA manual, it mentions that the implied seek is performed before a read or write command. So if it's before a command, that means before the data phase/transfer starts. I've also modified the read/write commands to perform an implied seek through normal …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2021-06-10, 20:59

I just thought of something: 0x200 is exactly the size of a floppy disk sector? And the sectors/cluster setting is exactly 1, so 512( =0x200 ) bytes is exactly 1 cluster? So it's the first cluster of NTDLL.DLL that's being incorrectly read somehow? Edit: The directory entry is at 0x4240 in the disk …

Re: Getting UniPCemu up and running

Posted on 2021-06-09, 11:05

Just the plain IBM VGA BIOS ROM in this case. Although I also used a modified ROM for floppy disk booting (with hardcoded IRQ, DMA and base I/O port) from the Generic Super PC/Turbo XT BIOS package if I remember correctly. 155.png That rom is first(for FDD) , XT-IDE 386 (for HDD) second and Plop 3rd …

Re: Getting UniPCemu up and running

Posted on 2021-06-09, 09:42

Are you using the correct architecture combined with the ROMs? It's only using the u13/15 ROMs with the Compaq Deskpro 386 and PS/2 architecture. Did you also add the required VGA ROMs if you're using a (S)VGA? I think everything is set up correctly. Attached are my settings. I am not using VGA yet …

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