Dos 7.1 FAT32 HDDs data corruption / disk operations related freezes. SCSI workaround and boot how to..

[ruthan]

Hello,
i have problem with some data reading related freezes.. I have 8 GB FAT32 drive, im emulating Pentium 200 machine with 32/64/128 ram. When i get some hard freeze, after reset i had problem, that.. i was got freezing during boot or during simple file system operation as dir command.

Fix is always open disk *img file, something and resave it.. Im using PowerIso for it, but it works same Winimage.

So it seems to, that there are happending some disk data corruptions on virtual hdd level, its quite often, so i dont thing its simple problem, which could be fixed by scandisk within virtual machine. I never had so much similar problems with real Dos machine.

Its know issue, or something specific for my setup? I simulated it on 2 different computers, which are otherwise stable.

[ruthan]

I tried multiple Socket 7 MB roms (FIC 503 / Shuttle 557 ) / CPUS and disk controllers, but its still the same - i got corruptions very often, it bug to be some bug. IDE XTIDE seems to be move "stable" than IDE - Standard IDE

Im using 2 GB and 8 GB Hdds:
2GB - Sectors 63, Heads 16, Cylinders: 4000, Size: 1968MB, *.img // System booting DOs 7.1 standalone no Win98 installed.
8GB - Sectors 63, Heads 16,Cylinders 16383, Size 8063 MB, *.img // Data

Host OS is Win 10 - 1909.

I would like to try SCSI controllers, but i dont know how setup it for boot, im using SCSI Adaptec AHA-1542C, setup same HDDs as for IDEs (which are booting fine) in configuration utility and set in Bios that SCSI is first boot device, but im still getting invalid boot device.. i never used SCSI back in day, so probably dont know something about its setup. How to select 1st booting device, termination etc.. I tried remove data disk, to ensure that its trying to boot from right drive, but it is still the same.

Also would be nice to have possibility to select IDE + SCSI together - because setting seems to IDE or SCSI (its just combobox). I would use IDE for boot disc and SCSI for Data disk.

I Bios is UDMA on, it could be problem too, is such option supported, tested?

I know that is corner case, but i have tried Q2DOS.. i dunno why, but here is storage performance very, very bad.. it block normal usage, for example title screen for Q2Dos take few minutes.. and loading of assets is after that is very slow too.

I also tried to move disk image to quick SSD - zero difference.

Screenshot from 2020-02-04 07-17-25.png (130.03 KiB) Viewed 14640 times

Screenshot from 2020-02-03 00-45-14.png (90.97 KiB) Viewed 14692 times

Screenshot from 2020-02-03 00-41-52.png (123.15 KiB) Viewed 14692 times

Screenshot from 2020-02-03 00-41-37.png (133.79 KiB) Viewed 14692 times

Screenshot from 2020-02-03 00-40-48.png (121.32 KiB) Viewed 14692 times

[ruthan]

Hmm, not able to make SCSI working with PCem.

I tried quite few 486 and Pentium MB machines, 5 SCSI controllers.. smaller hdd with FAT16 (250MB), but i always get that missing os or that disk is unbootable.. Disk image with IDE controller is booting fine, i even tried DOS 7.1 boot CD in SCSI CD rom, but its not booting too.

Can someone pleas test that SCSI boot is working for him with PCem and if yes, share config file or some hints?

[salocin]

Please try using Acronis or other drive cloner to clone from IDE to SCSI, offtopic but I have used Qemu's Q35 machine to install Win98 to ide and moved data to SCSI Drives via Acronis and got all drivers working, so i bet it works in PCEM.

I had to add a IDE controller, install OS to the IDE Drive and clone to the scsi drive/controller via Acronis when I did this in Qemu. Maybe boot to Acronis CD and clone ide drive to scsi. Initialize the new OS drive before writing and formatting via RAID/SCSI Bios if you can.

SCSI/Raid cards in RL even when using a single drive, can have some difference (encoding) in how drive is recognized by controller and it might not always work from an IDE/Sata Interface and vice versa, so you will want to clone to the new SCSI drive (new image file, and transfer data from the original image file. I use UltraIso for making boot CD's and Power Iso for editing HDD image files and it seems to works for all PC emulators that use img files for Fat16-32 from an IDE controller, not sure if it will read a drive from a SCSI Controller reliably.

Most Companies still have drivers and info on the web or try the win98SEB boot disk and see if that can find your drives and hdd on the available controllers. If push comes to shove make a dedicated boot disk to install dos/windows from ensure you get the right drivers. Also make sure to add all the drivers you can to the Windows CD/Folder you can to save time / headaches. OR lastly uninstall ide drivers shutdown boot to linux and sfdisk and rsync or ddrescue to the new drive and see if that works.

There were benefits to doing this in Qemu but I was on an ARMHF system and in that case using Q35 and SCSI was better for Win9X than the 430/PC target. IN PCEM on x86 I installed to a NVME drive and it worked at 1GB/S Speeds on the emulated IDE controller with some benchmarks so Im not sure if there is a actual performance need. I have not tried out PCEM on ARMHF Linux or tried SCSI support on x86 but I would like to try it out.

I suggest PCEM over qemu for retrogaming as there is no support interest for this from qemu, they will laugh at you. PCEM is great I have not touched VMware or VirtualBox in several years thankfully..

[ruthan]

So you are saying that IDE and SCSI disk images are not compatible, same as binary level? I though that they are, because when i switch from IDE to SCSI Pcem, still holds disk image file mapped on SCSI controller.

I have no idea how to convert img disk image with Acronis, on modern Windows, i would be first somehow mount img file as some drive letter.. and i dunno how.. if i would try to convert it right inside virtual machine, i would need some very old Acronis version (do you have magic number?), which is still running with very old hardware.. Yeah i can use QEMU which is supporting these img image, but its hassle on Windows too, so its my last choice.

So its SCSI PCem CD-ROm boot working for you? If yes which controller you are using?

[SA1988]

That "SCSI" boot sequence in the cmos means that the bios in question has got SCSI support only for a NCR/LSI 53c8xx adapter.

[ruthan]

Progress made, i used Adaptec virtual SCSI controller.. and tried to boot Windows 98 SE boot cd with it, but wanst able to do it.. I dunno where in SCSI adapter settings is something like boot device priority or which logic is boot priority based.

And because PCem cany combine SCSI and IDE - what is big flaw, i had to use boot floppies. Before that i formated HDD from SCSI controller menu, i dunno if it is needed, because regardless of that later Dos install make it again. Because of lack of IDE + SCSI i used only DOS 7.1 - 2 floppies and i was surprised that it saw my SCSI HDD without load of any additional driver as i would expect.. so such drivers are needed only for some controllers, but i would expect such thing mainly for Win98 where is see SCSI / IDE drivers loading sequence, DOS 7.1 boot install has nothing like that or its very quick.

After reboot now SCSI HDD image is finally working, so scored first victory and SCSI is somehow working with PCem, but far from done my research..

Now i would like to know:
1) is possible somehow recognize if disk image is IDE or SCSI format?
2) if Adaptec or any other supported PCem SCSI adapter is supporting SCSI CD-ROM boot and how to make it happen
3) How exactly convert IDE and SCSI img images and vice versa. Some PCem inbuild conversion would be really nice.

[ruthan]

Otherwise i cant be quite sure for such period of testing, but it seems that 486 machines are not corrupting disk image as Socket 7 and im using same disk images, so if is true it has to be bug.
I will check if disc corruption would happen with SCSI or not and if SCSI would minimize stuttering and occasional very, very slow disc operations.. and someone here already reported..

BTW its possible to move data from img to other with PowerISo directly without export it them to filesystem first? Update: Ok it is when you open 2 instances - you can drag and drop..

[ruthan]

Hmm, that is more strange have i connect second my old IDE data HDD, which was created with IDE controller to SCSI.. its working fine as second not boot HDD. So issue is related only to boot HDD and there some magic has to happen or its such some bug which is blocking to use image for both IDE and SCSI boot.

BTW how to setup Adapter SCSI controller CD-ROM in DOS? Which driver to use?

[ruthan]

Here is how to make CD-ROM working in Dos, im using generic device name CDROM i thing that is better and more universal for quick code using..

Ok CD-ROm driver is here - https://storage.microsemi.com/ja-jp/speed/scsi/dos/dosdrvr_exe.htm You can extract it by execution or even with 7zip on modern OS.

Autoexec Lines:
C:\DRIVERS\MSCDEX.EXE /E /D:CDROM

or optimal witth hardcoded driver letter:
C:\DRIVERS\MSCDEX.EXE /E /D:CDROM /L:E

Config lines:
DEVICEHIGH=C:\DRIVERS\SCSI\ASPI4DOS.SYS /D
DEVICEHIGH=C:\DRIVERS\SCSI\ASPICD.SYS /D:CDROM

[ruthan]

Ok rawspeed with SCSI now showing much reasonable speed that IDE controller, even when i enable controller how speed to 10 MB/s with emulated SS7 MB and Pentium 133 im getting 3-3.7 MB/s, but so far no strange freezes, it needs more testing.

Update: QDOS (3dfx ) and Q2DOS disk performance still sucks this code really doesnt PCem like.

[salocin]

Looks like at least Acronis 2011 and above needs cmov which is not present on the CPU's available. My apologies for missing that.

[leilei]

Cyrix 6x86MX / M II does CMOV

[ruthan]

Hmm, i did more testing, but so far no corruption with SCSI and FAT16 with IDE, so it really seems as problem with FAT32 + IDE only and maybe only with bigger disks, or Socket 7 platform, or only MS-DOS 7.1 - all these things together.
Update: SCSI is work around.. but present ISA SCSI controller have limitation with max 8 GB supported disk and speed 3-4 MB/s, no so great so i would be nice in future add some PCI SCSI controller.

[ruthan]

I test Q2DOS loading speed problem on second machine with Core i9 9900K and its the same.

[ruthan]

I still have this problem with PCem v17, when FAT32 image is connected at boot and something wrong happen, after reboot im stuck at the end of boot process and system not react. In not aware some problem with FAT16. Not im using PII emulation.
Im using in build IDE controllers.

Q2DOS slow loading times are related to EMM386 active and i can simulate it with other virtualization tools, so its not problem of Q2Dos not PCem.. If can add some logs etc, let me now. Im using same this images with Vmware, Vbox, Qemu and PCem and only PCem has this problem.. there could be errors on disk, but it should make boot freeze, when need disk are not boot device, only secondary. I thing that at end of boot process is my filemanager (File Wizzard) trying to scan all available disk and in that moment, it freeze because second this D is not working, available etc. Even i disconnect problematic disk image boot is fine, i tried add it as slave, master etc, it doesnt matter.

Only solution is return to backup of disk image.. I tried fixed size disk images and growing, original PCem formats, vhd, it doesnt matters, something is wrong.

[ruthan]

I had more time use Windows 98, there is some problem, sometimes when you get machine freeze (and if you get it because its Window9x.. or because PCem bugs), hard reset not working,sometimes even shutdown is not working, sometime some PCem process keep running after closing emulator.. But main problem is that these freeze, letting virtual disk in some inconsistent state.. so its completly unreadable and even boot sector can be readed (Disk boot failure, Insert system disk and press enter - Win98 boot message).
Its wrong by the design its not happening with other virtualization tools.. image header shouldnt be damaged unless you are doing something right before crash.. because there is some problem with closing file image right after writing to it, so its in inconsistent state when it is crashing..

[ruthan]

Other interesting thing is that when i attach some image as VHD in Windows, use Checkdisk.. im getting message that no errors found, but after that disk is bootable, so something had to be fixed with image.