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Re: DOSBox-X branch

Posted on 2013-10-28, 04:03

I have an interesting update about Windows 98: I don't have time to dig into the source code tonight, but I did another Win98 setup tonight and I noticed most of the crashiness and most of the random slowdown goes away if you set core=dynamic and cputype=pentium. The remainder of the crashes go away …

Re: DOSBox-X branch

Posted on 2013-10-27, 23:21

I'll check that code out when I have more free time next weekend. Right now, I'm certain my IDE emulation works properly with Windows 98 but I can't tell how reliable it is when it either crashes at random or runs the DOSBox VM at the speed of tar in freezing cold winter.

Re: DOSBox-X branch

Posted on 2013-10-27, 21:20

I just had a hunch about Windows 98: The minimum requirements are that it requires a 486DX or higher, right? Could it be that Windows 98 requires the use of the INVD/WBINVD and INVLPG instructions and that DOSBox is failing to emulate cache flushing that it expects? Perhaps their implementation …

Re: DOSBox-X branch

Posted on 2013-10-27, 20:26

OK. If you followed my advice and created a BIOS hard disk with 240 heads/track, there's a C/H/S calculation bug in the IDE READ/WRITE command emulation regarding multisector reads. The code assumes 16 heads/track when it increments through C/H/S addresses, so if you have 240 heads/track and IDE …

Re: DOSBox-X branch

Posted on 2013-10-27, 19:19

OK. One source of massive slowdown seems to be Win95 OSR2's preference for large read/write blocks combined with inappropriate delays coded into the IDE emulation. It's true that starting a READ operation might take 0.5-1ms, but on most drives the next sectors in the read operation usually come in a …

Re: DOSBox-X branch

Posted on 2013-10-27, 17:04

Mounting CDs has always worked so far, just add -ide 2m to the IMGMOUNT command to attach the CD-ROM to the secondary master IDE port and it should work. I think it hasn't "worked" yet for some people because there are possible mistakes in IDE auto-assignment that need to be worked out. (I …

Re: DOSBox-X branch

Posted on 2013-10-27, 16:32

OK I think this might help diagnose whatever is making Win98 crashy in DOSBox: I removed the Sound Blaster 16 driver from Safe mode and rebooted, and the slowdown and crashiness seems to have completely disappeared. I have a theory that this may have something to do with the KMixer component of …

Re: DOSBox-X branch

Posted on 2013-10-27, 16:16

OK. No matter what I do, IDE or not, Win98 will randomly crash at times. IDE emulation doesn't seem to help it any, but I don't think it's responsible. The only time Windows 98 is stable at all is if you boot into Safe Mode. I'm also noticing that while the dynamic core helps speed up emulation, it …

Re: DOSBox-X branch

Posted on 2013-10-27, 16:01

Update regarding Win98: I'm actually seeing quite a bit of crashiness with Win98. I'm not certain if my IDE emulation is at fault or not, I will investigate. Booting into Safe Mode seems to resolve a lot of it.

Re: DOSBox-X branch

Posted on 2013-10-27, 14:14

OK, the latest source code has been pushed to Hackipedia: http://hackipedia.org/Projects/DOSBox-X/dosbox-x-20131026-224002-commit-a051baa72a711d6b55b12f51cebbfeb5e6b4b826-src.tar.xz Note that I changed from SVN to GIT so new postings are now named dosbox-x- - -commit... As I mentioned in an earlier …

Re: DOSBox-X branch

Posted on 2013-10-27, 05:00

I'm also noticing that the Win95 OSR2 version of fdisk doesn't support hard drives larger than 8GB. You can use external linux tools to preformat a disk image for drives larger than 8GB, but if you try to create a primary partition from FDISK it only creates one that is 8GB or less.

Re: DOSBox-X branch

Posted on 2013-10-27, 04:49

Got it. Adding the same emulation to INT 13h AH=0x42 and patching the partition table to mark the FAT32 as LBA, also allowed OSR2 to fully use it's IDE driver on two 7.8GB hard disk images I made up. The only remaining hangup is that OSR2 periodically sends IDE command 0x40 (READ VERIFY SECTORS WITH …

Re: DOSBox-X branch

Posted on 2013-10-27, 03:18

OK. The fseek()/fread() failure was simply because I entered the wrong number of cylinders (too many) for what the file really contained. Fixing the cylinder count fixed the read error and Win95 OSR2 is able to use IDE emulation now. I also added code to Read_AbsoluteSector() to error out if it …

Re: DOSBox-X branch

Posted on 2013-10-27, 03:08

Confirmed: I think fread() is failing to read, yet the Read_AbsoluteSector() function doesn't check for failure to read. Zeroing the buffer before fread() makes the two consistent and Win95 OSR2 accepts our IDE emulation. I'm guessing this has something to do with the disk image exceeding 2GB in …

Re: DOSBox-X branch

Posted on 2013-10-27, 02:57

Okay, I see what the issue is: Windows 95 OSR2 does an INT 13h read from the start of the disk and then another read from about 90% out to the end of the disk. For some reason, a bug in the code is causing INT 13h to read a different sector from the IDE emulation, and that's why Windows 95 OSR2 is …

Re: DOSBox-X branch

Posted on 2013-10-27, 01:27

OK sorry, Win95 OSR2 does make the call to check for INT 13h extensions, but it doesn't seem to use them, at least so far. But the test it does doesn't work the same as Windows 95. I'm also getting a report at boot time (right about the time CONFIG.SYS is handled) that INT 13h was called from …

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