Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-22, 20:18

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by superfury

in PC Emulation

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I've moved PC Speaker buffering to the CPU thread(tickSpeakers function). Somehow I hear nasty pops in the sound? Anyone knows why? https://bitbucket.org/superfury/x86emu/src/dd … ker.c?at=master

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-21, 20:22

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by superfury

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I don't have real hardware to test it with, unfortunately. I've implemented the FIFO buffer in my latest build. CPU_readOP now tries to read from the FIFO if possible(fully filled for every instruction executed). When the FIFO is empty, the FIFO EIP to be read next instruction is updated with the …

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Re: x86EMU emulator releases

Posted on 2015-11-21, 19:56

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by superfury

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I'll test those changes later. My latest x86EMU build: x86EMU_20151121_1846.zip - Fixed PS/2 mouse missing IRQ handling. - Implemented prefetching for all CPUs. Edit: I've tried your instructions. It now installs correctly (I didn't closed the window when it told me to during installation). I've …

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Re: VGA VRAM read/write multithread locking required?

Posted on 2015-11-20, 12:51

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by superfury

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Emulated VRAM doesn't have locks. The main thread reads and writes to emulated VRAM. The rendering thread only reads from emulated VRAM. Any VGA register changes (resolution changes and other settings of the VGA) are protected with locks when updating the renderer information from the CPU thread( …

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Re: x86EMU emulator releases

Posted on 2015-11-20, 12:39

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by superfury

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I get some errors running the SDL-install: Unpacking "SDL-1.2.15.zip" into "C:\MinGW\src". 'sh' is not recognized as an internal or external command, operable program or batch file. 'sh' is not recognized as an internal or external command, operable program or batch file. 'sh' is not recognized as …

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VGA VRAM read/write multithread locking required?

Posted on 2015-11-18, 00:52

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by superfury

in PC Emulation

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I have the main thread(CPU emulation) writing and reading emulated VGA vram memory. There's also a timer thread reading that memory and writing it to the emulator display buffer. Will CPU emulation reads/writes produce errors reading/writing the emulated VRAM? Or will only the renderer produce …

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Re: x86EMU emulator releases

Posted on 2015-11-18, 00:32

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by superfury

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I also try to get MinGW set up and running, but it won't work installing according to the basic manual, then compiling SDL 1.X (Latest version as far as I can remember). It gives me a lot of compile errors about stuff not being found etc. After that I still need to compile SDL_gfx and then my own …

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Re: x86EMU emulator releases

Posted on 2015-11-17, 16:04

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by superfury

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You need the Visual C++ 2015(community) runtime redistributable in order to run it.

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-16, 16:29

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by superfury

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What about MMI/O, like VGA VRAM? When the prefetch reads VRAM which is protected(but protection is ignored or simply too far past the code to be executed), it might cause the VGA memory latches to be loaded when actually they shouldn't? Like REP STOSW; RET just before VRAM, at address 9000:FFFD ( …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-16, 15:41

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by superfury

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If I call MMU_rb for any illegal segment:offset(it executes both paging and segment protection emulation as well as read the data from emulated memory) from the prefetch buffer filling routine, it will always raise exceptions after 16 bytes before the end of the code segment: IP+prefetchsize>=CS. …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-16, 14:56

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by superfury

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The problem is that if I remove the call to MMU_rb(which is also used during normal memory accesses by the CPU) and replace it with a direct memory approach (needing a complete copy of the entire memory module, the CPU emulation won't have ANY protection left anymore. No exceptions will be triggered …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-16, 13:14

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by superfury

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When 16 bytes of memory data are prefetched in protected mode and I read the prefetch buffer from memory with less than 16 bytes left in the code segment it will raise an exception, even when less than 16 bytes are actually executed (since it will try to read past the end of the code segment, …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-16, 12:52

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by superfury

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Well, the protection is handled by the MMU during all memory reads/writes (including CPU instruction reads). So when an instructions reads data from memory (any instruction opcode/parameter) an exception is triggered and executed after which the CPU core itself aborts executing the instruction when …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-16, 07:57

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by superfury

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This shouldn't be a problem during real mode. But what happens when prefetching in protected mode? How is memory protection and paging handled with prefetching? Does the prefetch not read memory past the segment limit? Will it error out when less than 15 bytes before the end of the code segment? …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-15, 11:49

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by superfury

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There's still another problem: with a 4-byte FIFO, how do I handle instructions with a length of more than 4 bytes? Fetch directly from memory instead of FIFO past the 4th byte? E.g. MOV modr/m addr16 imm16 is a 6 bytes long instruction. Only 4 bytes can be loaded into the prefetch buffer. Should my …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-13, 22:54

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by superfury

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What about repeating instructions, like REP MOVSB/W? So I need to do the buffer loading after (E)IP is reset after the instruction to catch those. What about more instructions that need to be pipelined? Like REP MOVSB followed by a second instruction needed to be executed from the same pipeline …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-13, 16:11

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by superfury

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The problem is that my CPU emulation decodes the data from memory while executing it: First is a little loop: - Fetch byte from CS:(E)IP. - If prefix, set flag and loop, else run opcode handler from lookup table. The opcode handler from the lookup table: - Fetch ModR/M byte if needed. - Fetch SIB …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-13, 15:31

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by superfury

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in PC Emulation

Any tips on how to archieve this 'prefetch buffer' emulation (it's currently fetching all instructions directly from memory using CS and (E)IP)?

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-13, 13:43

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by superfury

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I've updated the PIT: https://bitbucket.org/superfury/x86emu/src/87d5a990932b3aea49eb816696815b1ba4509a85/hardware/pit.c?at=master It seesm to continue running now. It lags a bit at some times, but continues as it should. I get some screens with static noise on the screen. Eventually the Hornet etc. …

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Re: x86EMU 4-color CGA mode fails retrieving graphics pixels completely?

Posted on 2015-11-12, 23:05

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by superfury

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I've fixed the timing a bit: https://bitbucket.org/superfury/x86emu/src/2485499d38704dcfe4e24e9afe57ec102b63bf2c/hardware/pit.c?at=master. The application does tell me it's detecting the CPU running at 0% speed of a 8086 (according to MIPS 1.10, it's actually running at up to 2.56x 8086 speed. …

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