Re: x86 LOCK signal vs DMA?

Posted on 2019-05-13, 12:28

by

by superfury

in PC Emulation

in PC Emulation

Just implemented the lock signal to happen from the first memory I/O until the instruction finishes(e.g. during it's final cycles after the memory accesses, until the next instruction is going to start at the next cycle(the BIU is already finished doing it's work for the currently executing …

---

x86 LOCK signal vs DMA?

Posted on 2019-05-13, 10:17

by

by superfury

in PC Emulation

in PC Emulation

Does the lock have effect on DMA and it's transfers? I only read it having effect on multiprocessor systems(multiple cores?)?

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-12, 15:11

by

by superfury

in PC Emulation

in PC Emulation

Just completed the Pentium emulation by implementing the few 0F opcodes that were added with it(0F30-0F32 and 0FC7, the P1+ tagged instructions at x86.refasm.net's coder32 edition). Now the only Pentium features left unimplemented are the VME extensions(PVI and the V86-mode extensions) and Machine …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-10, 13:35

by

by superfury

in PC Emulation

in PC Emulation

Just saw something interesting running Windows 3.0a in 386 enhanced mode(just before it crashes to the MS-DOS prompt): I see it's throwing a #GP(0) fault on accessing the DS segment, which is a descriptor loaded with a limit of 0? That seems kind of strange? It's base is 0x20(which is strange as …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-10, 09:56

by

by superfury

in PC Emulation

in PC Emulation

One interesting thing to note: When running certain MS-DOS games(alley cat, ultima ii) in full screen, then switching to windows using alt-carriage return works fine, starting it from the MS-DOS prompt(perhaps graphics mode switching itself) in windowed mode inside 3.1(1) causes it to somehow crash …

---

x86 page fault priority?

Posted on 2019-05-10, 07:52

by

by superfury

in PC Emulation

in PC Emulation

When an entry isn't found in the TLB and to be loaded from memory, what is the order of page fault checks that are executed? There's checking on the PDE's Present bit, the PTE's present bit and the rights(privilege and read/write). It currently first checks the PDE's present bit, then the PTE's …

---

x86 IDT access rights size bit(bit 3) effect?

Posted on 2019-05-09, 21:34

by

by superfury

in PC Emulation

in PC Emulation

What does the IDT's Access Rights' Size-bit control(bit 3 of the Access Rights for Interrupt and Trap gates)? All I can find are descriptions saying 16-bit for 0 and 32-bit for 1. But there's no explanation I can find ANYWHERE what this bitness applies to? It can't be stack size, as that's done by …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-09, 08:37

by

by superfury

in PC Emulation

in PC Emulation

Just found and fixed a 80(1)86-specific bug, which caused the GRP5 PUSH r/m16 to push the old SP value(like a 80286+ CPU) instead of it's correct 8086 behaviour(pusing the SP value after it has been decremented by 2). Although that doesn't affect 80386+ emulation(because it's a 80(1)8X-specific …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-08, 22:16

by

by superfury

in PC Emulation

in PC Emulation

Looking at your emulator, I see x86 interrupts from V86 mode to 16-bit interrupt/trap gate actually pushing words instead of dwords? But IRET doesn't do anything that reverses said behaviour, only IRETD does(properly handling like a 32-bit interrupt return to V86 mode)? Or is the OS supposed to …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-08, 21:37

by

by superfury

in PC Emulation

in PC Emulation

Will 16-bit gates affect stack pushes to become 16-bit at all? If EFLAGS is pushed as 16-bits, VM won't be restored properly during IRET? Since 16-bit pushes during INT require 16-bits pops during IRET, but EFLAGS.VM is truncated off, so that can't work? How does your emulator handle that? Force 32- …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-08, 05:07

by

by superfury

in PC Emulation

in PC Emulation

Just tried to install Internet Explorer 5.0 (5.0.0913.2200) for Windows 3.x on WFW 3.11. It seems to succeed at part of the full installation(the very first one), but once it gets to the Internet Explorer installation step(the second step of of 6), I see the rest of the steps failing with red X'es, …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-06, 09:17

by

by superfury

in PC Emulation

in PC Emulation

Well, I see that emm386(either windows 3.x or MS-DOS 6.22's or both) seems to use a 16-bit IDT gate. But that doesn't combine with IRETD if it pushes 16-bits entries(as IRET would pop FLAGS instead of EFLAGS, setting EFLAGS.VM incorrectly)?

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-06, 05:04

by

by superfury

in PC Emulation

in PC Emulation

Doesn't that cause troubles when using IRETD to return to the V86 task? Since IRETD always pops DWORDS?

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-06, 02:37

by

by superfury

in PC Emulation

in PC Emulation

And what effect does the interrupt descriptor size(16 vs 32-bit) have on pushes on the stack during an interrupt or fault from V86 mode? Is it always only pushing 32-bit entries on the stack(for the segments, SS, ESP, EFLAGS, CS and EIP), only affecting the masking of EIP to load 16-bits of IP data …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-05, 20:06

by

by superfury

in PC Emulation

in PC Emulation

Anyone knows what effect the operand size has on 16-bit segment register push operations? Are they pushed zero-extended to 32-bits? Also, what effect does the gate descriptor size(16-bit vs 32-bit gate, so bit 3 of the Access Rights byte of the IDT entry) within an IDT have on interruots from V86- …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-05, 17:03

by

by superfury

in PC Emulation

in PC Emulation

One interesting thing to report now: after improving 16-bit pushes to write 16-bits to memory or 32-bits when the operand size is 32-bits(zero-extending), I now see Windows 3.0a throwing a Page fault on address A0000. So that means the primary loading of the kernel is succeeding and it's progressing …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-04, 20:01

by

by superfury

in PC Emulation

in PC Emulation

Interestingly, Linux crashes in a far return(opcode C3) to 0x79536e61, while the CS has a limit of 3FFFFFFF(the top part of the 32-bit address space). It's in kernel mode at said point. It happens at 0010:001e3439. That's an invalid return address. Probably something set up by code? Edit: I've …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-04, 13:54

by

by superfury

in PC Emulation

in PC Emulation

Trying it with Windows 98 (which was copied to c: by a sys command) results in WIndows complaining about it: You started your computer with a version of MS-DOS incompatible with this version of Windows. Insert a Startup diskette matching this version of Windows and then restart. The system has been …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-03, 15:57

by

by superfury

in PC Emulation

in PC Emulation

The game I'm trying(Pink Panther in Hocus Pocus Pink) is running using win32s afaik. Could it be that what's crashing the Windows 3.11 environment(triple fault) is actually the win32s drivers themselves? Or is that just a bug in my CPU emulation? Edit: Just tried Windows 3.1 in 386 enhanced mode. It …

---

Re: Any good MS-DOS 80386/80486 games for testing Virtual memory support?

Posted on 2019-05-03, 14:01

by

by superfury

in PC Emulation

in PC Emulation

Well, the display is even higher than that atm. It's at 800x600x64K colors(the emulated ET4000 in it's maximum color depth setting). It's still strange that Windows triple faults on it's own stack. Is that a CPU bug, or is that common behaviour for win32s or the Windows for Workgroups 3.11 kernel? …

---