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Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on Today, 02:19

in PC Emulation

in PC Emulation

And the latest bugfix on the 8042's output port (to ignore the bits 4-5 written on i4x0 devices to not trigger IRQs all the time) should fix the spurious 8042 IRQs with nothing buffered. Now Windows 95 changes behaviour once again, trying to load a GDT entry that's out of range this time instead ( …

Re: 8042 output port bits 4/5?

Posted on Today, 01:16

in PC Emulation

in PC Emulation

Although this issue is old, I noticed one odd thing with the latest CPU bugfixes. When the BIOS executes, I see it writing 0xDD and 0xDF to the output port for some odd reason, on the i440fx (don't know about other architectures yet)? It's probably enabling and disabling the A20 line, but also keeps …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on Yesterday, 22:03

in PC Emulation

in PC Emulation

OK. Just was interested and ran the test386.asm testsuite once again (Pentium II for all emulation support on the Compaq Deskpro 386 architecture). It ends up at POST 12h. So something is definitely wrong now, in the CPU emulation. The documentation of test386.asm says: Other memory access faults …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-28, 10:12

in PC Emulation

in PC Emulation

And did the same to handling. Trap flag also now gets ignored if it detects a SMI at the same time, giving priority and ignoring the trap flag handling.

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-28, 08:57

in PC Emulation

in PC Emulation

Moved both SMI and hardware interrupts(INTA to be exact) from (A)PIC (both use INTA timings right now) to be handled as special and instructions, instead of being fused into the first instruction after it. That simplifies handling both of them to be like normal instructions and improve searchability …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-27, 14:26

in PC Emulation

in PC Emulation

Just fixed an 'issue' where 80286+ GRP4/5 INC/DEC opcodes would check against read accesses first, then check against r/w accesses, instead of only checking against r/w accesses. This was introduced with the new handling of the GRP4 opcodes (and already invalidly present on GRP5 opcodes). That would …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-25, 10:08

in PC Emulation

in PC Emulation

Managed to fix one other bug exposed by SDL3 (SDL2 somehow doesn't seem to show the bug). There was an issue with multithreaded pointer registration and release that caused the memory allocations for disk write file structure allocations to fail, causing the disk write to fail, for example when an …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-24, 19:36

in PC Emulation

in PC Emulation

OK. With the latest interrupt bugfixes and other CPU improvements (things like improved B-bit handling and D-bit based protected mode handling from the source segment of interrupts, faults and far jump/call/ret and iret instructions) Windows 95 goes wrong during any boot it seems? It's trying to …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-23, 11:29

in PC Emulation

in PC Emulation

Managed to fix an issue in the new SDL3 port of the common emulator framework. So now sound works properly again on SDL3. Also went and fixed some issues in sound device connection/disconnection on SDL2/3.

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-22, 02:37

in PC Emulation

in PC Emulation

Just fixed a i82347 bug where the NMIMASK register was set to mask the wrong causes and could cause an NMI in various cases (due to swapping reset state of register C3h and C4h (register C4h set to 84h and C3h set to 00h). They're now properly set to 84h(for register C3h) and 3Eh(for register C4h). …

x86 Trap Flag during IRET in VME?

Posted on 2024-04-21, 22:35

in PC Emulation

in PC Emulation

What is the real behaviour of the trap flag during IRET in VME mode? When the trap flag is set during a Virtual 8086 mode 16-bit IRET instruction (by the value popped into the FLAGS register's 13 bits (IOPL, Interrupt flag(popped into VIF instead) (and Virtual 8086 mode flag as well, but isn't …

Re: x86 NT(Nested Task) flag vs VM flag?

Posted on 2024-04-21, 21:46

in PC Emulation

in PC Emulation

So, if the NT flag is essentially unsupported in V86 mode(only being cleared/set during task switches, but having no effect on IRET), is it affected by task switches to V86 tasks? So a CALL to a V86 task, will that set the NT flag of said task? Will it have effect on the V86 task(besides it being …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-21, 01:26

in PC Emulation

in PC Emulation

OK. APM probably works fine I think. I noticed something odd when running an already installed Windows 95 OSR 2.5 from earlier builds. It booted up fine. Then once clicking the start menu it kept BSOD-ing at C000E975 (not sure about that first part tho, so more like CxxxE975). So I put up a …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-19, 07:18

in PC Emulation

in PC Emulation

Oh great. Now with the latest changes, Windows 95 OSR 2.5's first boot fails: Windows Protection Error while initializing device CONFIGMG. Didn't get that error code before I think? Perhaps APM-related?

Re: Can 32-bit x86 programs explicitly use IP?

Posted on 2024-04-18, 12:50

in PC Emulation

in PC Emulation

Slightly related, since it applies to EIP or IP: What is the return point of a interrupt handling throwing a fault (for example #GP) during an INT instruction itself (opcode CDh)? UniPCemu currently treats all faults the same (resetting EIP to the start of the instruction), but is the same true for …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-18, 12:43

in PC Emulation

in PC Emulation

Just found a tiny issue with the LEAVE instruction that caused paging TLB loads on the stack reads not to continue the instruction with the proper ESP register state if the stack pop caused a TLB load to require locking the bus (which TLB loads always do, unless the bus is already locked and owned …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-17, 16:04

in PC Emulation

in PC Emulation

Hmmm... Running WFW 3.11 in 386 enhanced mode crashes PROGMAN. But running Windows 3.11 in Standard mode doesn't crash it? Although it can't install because it's seemingly trying to run the installer in MS-DOS mode when it's run on Windows 3.1 in 386 enhanced mode? Edit: Just found out that although …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-14, 15:35

in PC Emulation

in PC Emulation

Fixed 32-bit operand size for far calls. Also implemented changed D/B-bit checks according to Bochs's (E)SP and (E)IP behaviour. Also fixed 32-bit far calls to behave properly again, when not through call gates. (E)IP itself doesn't seem to have issues anymore on 80386+, but Windows 95 OSR 2.5 "C" …

Re: Emulating Area5150

Posted on 2024-04-14, 02:13

in PC Emulation

in PC Emulation

Perhaps a bit related to the whole 8088 accuracy one. Just found this description of pretty much all 808x microcoded (undocumented/missing) opcodes and their behaviour: https://www.righto.com/2023/07/undocumented-8086-instructions.html Might be interesting to implement one day? I have some already …

Re: Testing and fixing UniPCemu's CPU and UniPCemu progress

Posted on 2024-04-13, 13:25

in PC Emulation

in PC Emulation

OK. With the latest improvements to the 32-bit TSS IOPB's limit range checks, I see something interesting happening during phase 2 of the Windows 9x setup: "An exception 0E has occurred at 0028:c0007292 in Vxd ---. This was called from 0028:C10555BC in VxD ---. It may be possible to continue …

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