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Re: Effect of CS,DS,ES,FS,GS DPL in descriptor cache?

Posted on 2019-03-10, 23:28

Thinking about it, how does INVLPG work? UniPCemu currently takes the ModR/M segment:offset it refers to(e.g. DS:[EAX] will use linear address DS.base+EAX) and flush any entries that match said address(E.g. when DS points to address 100 and EAX=2000, it flushes the entry/entries for linear address …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-10, 20:44

One interesting thing is that hal.dll seems to either call or fault into the ntoskrnl, according to the stack trace that's displayed. Would that happen on a normal boot of Windows NT 3.1? Is it legal to make hal.dll calling or faulting into the ntoskrnl image(as hal.dll is sandwitched between two …

Re: Effect of CS,DS,ES,FS,GS DPL in descriptor cache?

Posted on 2019-03-10, 16:50

Hmmmm... http://www.rcollins.org/articles/loadall/tspec_a3_doc.html#Fig2b Intel recommends some guidelines for proper execution following LOADALL. The stack segment should be a read/write data segment; the code segment can be execute on1y (access=95h), read/execute (access=9bh), or read/write/ …

Effect of CS,DS,ES,FS,GS DPL in descriptor cache?

Posted on 2019-03-10, 16:24

According to http://www.rcollins.org/Productivity/DescriptorCache.html , the CS.DPL==SS.DPL(in reality only SS.DPL afaik?) determines the CPL. But what effect does DS.DPL, ES.DPL, FS.DPL and GS.DPL have on executing code? Afaik they don't have any effect on segment loads(only SS.DPL, which is CPL …

Re: Windows NT not detecting ATA(PI) HDD and CD-ROM?

Posted on 2019-03-08, 17:25

Just found out some bug in my ATAPI emulation. The result of the Read Capacity command was backwards, in little endian format, instead of big endian format(as is supposed to be the case). Whoops! Edit: The same appears to have been wrong with the sector size reported by the very same command. …

Re: x86 CPU shutdown cycle effect on A20?

Posted on 2019-03-08, 14:05

So, a normal CPU reset(using the 8042 output port and system control port A(port 92h)) will leave the A20 line alone(other than their own effects, being written to setting said gate appropriately), but a shutdown signal on yhe bus(by the CPU) will always set A20 to be enabled?

Re: x86 CPU reset/shutdown cycle effect on A20?

Posted on 2019-03-06, 20:43

So, in short, what happens when a triple fault occurs and A20 is gated off(forced to 0), so triggered by e.g. LIDT a limit of 0 in real mode and then raising an interrupt? Is A20 automatically enabled when the motherboard receives a shutdown cycle on it's bus? So (in real mode): lidt cs:[invidtr] …

x86 CPU shutdown cycle effect on A20?

Posted on 2019-03-04, 22:05

I know some code can disable A20 and triple fault/hardware CPU reset(using e.g. the 8042 Controller or the system board port B) etc. to generate a CPU reset and catch the CPU information stored in EDX::EAX(model number etc.) after reset using a #UD handler installed in memory. Isn't A20 supposed to …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-04, 19:18

Now trying to reinstall Windows 95a again. Maybe it'll fix the problems that occur during first boot(corrupted files)? Or perhaps the problem stays, because a CPU problem still exists? Only time will tell. Edit: The crash from safe mode after rebooting Windows 95 still happens at exactly the same …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-03, 17:24

After rebooting after copying disk 9 with the correct Ctrl+Alt+Del, it still crashes at the same point(with error code 0000007B (0xFF831BA8, 0x00000000, 0x00000000, 0x00000000)). Although that second number seems to have changed to FF831BA8 instead, compared to earlier BSODs.

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-03, 02:40

I adjusted the timings according to PCem's multiplier, but on UniPCemu's ATAPI result timing(7ns). So 7ns for the packet command, and all others multiplied by integer factiors(PCem's https://bitbucket.org/pcem_emulator/pcem/src/default/src/ide.c based timings, so ATAPI PACKET is 7us times 1, seeks …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-03, 00:12

One interesting thing is that during the Windows 3.1 setup's first phase(through 9 floppy disks), it asks to press Ctrl+Alt+Delete to reboot the computer. But since that doesn't work(for some reason), I use the emulator's functionality to reboot instead(using a cold reboot). Will that cause problems …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-02, 22:18

Hmmmm.... Something interesting happens when I use the ET4000 to run the Windows NT Hardware Qualifier disk(created under Dosbox from the CD-ROM disk image and an UniPCemu-created 1.44MB floppy disk iamge). When running with the ET4000 hardware, the screen gets messed up. Edit: Interestingly, …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-02, 13:06

I've adjusted it a bit, according to the PCem timing(based on the base timing, which I've assumed from the PCem source code to be the the ATAPI_PENDINGEXECUTETRANSFER_RESULTTIMING, which is 7us). Then I modified all timings to use the same multipliers as PCem does(based on https://bitbucket.org/pcem …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-02, 10:58

So, how accurate does the timing need to be? Do I need to implement all the ATA-1 timings exactly, or only adjust the interrupt timings? Edit: It now has: - 300ms until reset complete. - 670ns until raising IRQ(after finishing a command). - 50us for a drive select. All other timings are 0ns(no delay …

Re: Windows NT not detecting ATA(PI) HDD and CD-ROM?

Posted on 2019-03-02, 10:12

Another strange thing is, I've managed to find the data for the SP6 floppy ATAPI.EXE (From https://www.helpjet.net/Fs-85106202-75843699-43936582-extract.html ) that's supposed to improve large hdd support. I've opened it with 7-zip, extracted it's contents, then copied that to a freshly generated 1. …

Windows NT not detecting ATA(PI) HDD and CD-ROM?

Posted on 2019-03-01, 18:38

I see it's defaulting to the SCSI hard drive/CD-ROM drivers, while it's supposed to be using ATA(for HDD) and ATAPI(for CD-ROM) drivers instead? Anyone has an idea how to fix this? I'm using a Compaq Deskpro 386 emulation (UniPCemu) with the XT-IDE HDD BIOS for hard disk booting(and floppy disk …

Re: UniPCemu Windows 95/NT progress and issues

Posted on 2019-03-01, 17:04

Just tried Windows NT 4.0 Workstation, which crashes with the same error message: Filename 1058-Windows NT 4.0 disk 2 BSOD.jpg File size 253.71 KiB Views 586 views File comment Disk 2 of the floppy boot gives a BSOD. Interestingly in all cases, I see that some SCSI driver is loaded, but no required …

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