Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-10, 22:14

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by superfury

in PC Emulation

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That wouldn't be, by accident, be the 'common' bug of entering protected mode setting the PM bit? Thus reloading all segment registers? Nothing is reloaded after all, everything works like in real mode, until interrupts(protected-mode style) and segment register loads(protected-mode style) occur. …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-09, 17:08

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by superfury

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Now trying MS-DOS 7.0(Windows 95a bootdisk) on the Compaq Deskpro 386. The VGA is rendering nothing and is pretty impossible set-up: X resolution: 1008 raster pixels(horizontal total origin). Horizontal display start: 0(end 729). Horizontal blanking start: 819(end 10), Horizontal retrace start: 288( …

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Re: UniPCemu emulator releases

Posted on 2018-02-09, 09:21

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by superfury

in Release Announcements

in Release Announcements

All UniPCemu releases(including PSP builds) and update information can now be found at the itch.io website! So from now on all in one place! 😁

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-07, 17:24

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by superfury

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This is what I currently get when booting MS-DOS 6.22 on the Compaq Deskpro with the FDD DMA hack enabled(incorrectly setting the DMA mode register to 0x42 instead of 0x46, causing the DMA to perform a self-test(no I/O or memory transactions) instead of FDC to memory transfer): debugger.log …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-07, 14:26

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by superfury

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Manually forcing the Verify mode on the DMA channel for the FDC to become a Write memory mode(mode 1) makes it properly boot from the floppy disk(MS-DOS 3.3)? So it's only a problem with the CPU somehow being incorrect somewhere along the way? As far as I can see, the instruction that loads the …

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Re: test386.asm CPU tester

Posted on 2018-02-07, 14:00

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by superfury

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Now the 80386+ and 80486+ instructions are also modified to use the lookup table. The instruction tables(which details instruction rights(like LOCKable, valid modr/m reg values for immediate bytes or not etc.) and the parsing of the modr/m parameters and immediate parameters) also seems fine now. …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-06, 14:48

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by superfury

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Looking at the source code of the disassembled BIOS, I'm questioning the saneness of the BIOS itself: why would it overwrite the function number, which is used to properly execute a FDC/DMA command combination, with the unchanging value 4? Thus it would be executing a sort of Verify command each …

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Re: Finding bugs in 8086-80386 emulation core?

Posted on 2018-02-06, 07:40

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by superfury

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I've just tried running the Compaq Deskpro 386 BIOS again in cycle-accurate mode. Somehow. it never enables a DMA channel(mask is set to 0xF, thus all channels are masked off), then proceeds to boot and finally hang on waiting for bit 0 of the channel 0 high/low counter to change?

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Re: Finding bugs in 8086-80386 emulation core?

Posted on 2018-02-05, 13:04

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by superfury

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Just tried booting MS-DOS 6.22 on the XT (80186 CPU). It seems to crash somewhere within IO.SYS, at 0070:0003 with a DIV instruction faulting to the BIOS and returning. I don't think that's supposed to happen? Guess I'll try and single-step through the whole driver running and see what it's doing( …

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Re: UniPCemu emulator releases

Posted on 2018-02-05, 12:24

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by superfury

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A quick little update: UniPCemu_20180205_1300_PSP.zip Changelog: - Optimized normal and stack address checks with unlikely statements and more efficient checking. - Optimized all modr/m checks by adding unlikely and reducing modrm checks to actually execute only once for an instruction. - Applied …

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Re: PCem - possible to run in 320x200, and/or above 60hz refresh?

Posted on 2018-02-05, 01:20

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by superfury

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PCem will scale the emulated display to whatever resolution/refresh rate your desktop is running at - it makes no attempt to change either. Whoops, you're right. I forgot that it's running inside an emulator, since bluejeans started talking about a crt, which is controlled by the OS running the …

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Re: UniPCemu emulator releases

Posted on 2018-02-04, 15:42

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by superfury

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A new UniPCemu release, with various improvements: UniPCemu_20180204_1602_PSP.zip Changes: - Fixed IDE memset to use correct pointers for clearing buffers. - Implemented the Microsoft Corporation: Media Status Notification Support Specification, Version 1.03 into the CD-ROM drives, in limited form( …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-04, 13:05

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by superfury

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Now the only question left: what causes the invalid jump from IO.SYS(MS-DOS 6.22) and XT-IDE AT ROM(Trying to reboot after invalid boot). Edit: There's also the strange case of the Compaq Deskpro 386 crashing due to invalid programming of the DMA channel 0 when using a CGA/MDA adapter. And there's …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-04, 10:29

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by superfury

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Just removed all those MMU.invaddr checks from the instructions. It gets set on faulting memory transactions, which is not used by the EU directly(imaging word accessing end of RAM(Valid) and one byte further(Invalid) aborting the whole transaction, while a real CPU just reads 0xFFxx or writes the …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-03, 16:10

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by superfury

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Just looked through the code that handles a new instruction being read: the new opcode active information is only reset/loaded when an instruction is conpletely fetched&decoded(starting to pend the modr/m decode phase). Only then does it clear the stepping states, thus it indicates that an modr/m …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-03, 15:47

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by superfury

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Could it be that the error is caused by an external influence, like an incorrectly triggering hardware interrupt in the middle of handling a BIU request/response combination? The logic for it to trigger is currently very simple, but it shouldn't happen when an instruction is running(it only checks …

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Re: PCem - possible to run in 320x200, and/or above 60hz refresh?

Posted on 2018-02-03, 10:04

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by superfury

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It's usually a 320x200 framebuffer, upscaled to 720x400 using double scanning and half pixel clocking as far as I know(CGA doesn't afaik). The refresh rate is usually dependent on the output resolution (720x400 with front and back porch added) and the clock used(in this case 25MHz divided by 720(+ …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-01, 22:24

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by superfury

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Strange that the incomplete transfer still occurs: I've checked each and every transfer function giving such requests to the BIU, and each of them has a proper request and response stage in the common I/O, direct memory and modr/m handlers? Could it be some problem with non-memory transfers(BUS(I/O …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-01, 19:30

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by superfury

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Just modified all EU instruction handers to check perform memory checks that are used in an instruction only once during it's runtime(based on the current instruction step). That should prevent memory updates from influencing behaviour of the current instruction(although afaik there are none), while …

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Re: UniPCemu IBM AT/Compaq Deskpro 386 emulation FDC/DMA issues?

Posted on 2018-02-01, 08:48

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by superfury

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Since it is memory refresh, highest of all. That cannot be: the CPU in my emulator provides the base timing for ALL hardware, thus it'll need to execute first. Also, memory refresh can't execute while the CPU is using the BUS? When it's not in T1 while not transferring anything(idle bus cycle of …

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