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Did Windows 95 replace the INT13h service routine?

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First post, by serialShinobi

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I am referring to a page from my motherboard manual:

To support LBA or LARGE mode, there are softwares located in the AWARD HD Service Routine“INT13H”. It may fail to access a HDD with LBA or LARGE modes selected if you are running under an Operating System that replaces the whole INT13H service routine.

Motherboard is an ESA tf-486 with AMD 486 processor and EIDE headers on the motherboard and communication by PCI bus. Manufactured in 1999 has a single PCI slot and several ISA.

In the PCI slot I have a Promise Technology Ultra ATA-33 interface connected to a 3.4 GB EIDE Ulta ATA-33 Samsung VG33402A disk. My Promise Technology PCI card auto detects this drive and I was able to use a Windows 95 OSRv2 floppy to boot and initialize the hard drive. Using a modern laptop with reader I had a CF card with files cut and pasted from a Windows 95 OSRv2 CD image. I successfully installed Windows 95 on the hard drive and later booted to the Windows 95 desktop. The only problem is I need a working CD-ROM drive and the one I have works if connected to the motherboard but not if connected to the Promise Technology PCI card. The Ultra ATA-33 PCI interface won't detect the CD-ROM and The WIN 95 MSCDEX.EXE sees no drives. Computer freezes before boot if the PCI interface and the motherboard interface is used.

Maybe I could yet use my Windows 95 hard drive with the motherboard headers? I would use the Samsung hard drive on header PIDE1 for primary and CD-ROM drive on PIDE2 for secondary. But the Samsung VG3400 gets detected by the Award BIOS detect and configure tool...sets it up as 3400MB in LBA Mode sometimes switching to CHS mode...but the CHS matches what's on the hard drive label. The use of the motherboard interface results in a hang before booting to the operating system.

Were there operating systems that caused problems for motherboard interfaces and BIOS Boot functions? Could Windows 95 be my problem? Maybe Windows 95 isn't compatible with INT13h? Do you suggest I try a different OS? Did Windows 98 fix boot problems created by Win95?

Reply 1 of 2, by Ryccardo

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IIRC Windows 3.1[1] does provide its own int13 implementation if you're using "32 bit disk access" (= an actual Windows HDD driver, instead of [a ROM or DOS one = whatever implementation of int13 before booting the OS]), so I would guess the same is true in 9x except for "32 bit" drivers being more common and indeed enabled by default 😀
Does safe mode work? (It should have "32 bit" force disabled)

The manual refers to the general problem with mixing CHS and LBA modes on different implementations/settings of the conversion function: that option (Normal/Large/LBA) applies to CHS accesses going through the BIOS (which provides the default int13 before Option ROMs and software equivalents can supplement/override/replace it)

In my experience, operating systems that ditch int13 ASAP ("today's" Linux and OpenBSD) are more compatible than those that don't!
But of course this fact, true on an Igel M310C with large CF cards, is not universal...

Reply 2 of 2, by Horun

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Which version of Windows 95 ? Native OSR2 supports to 32Gb partition but original Windows 95 only supports 2Gb max partition....

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

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