PDA

View Full Version : DOS 3.3 - FDISK question



twqwctf
December 26th, 2015, 02:36 PM
Hi, I have a vintage Toshiba T3100e/40 here I got from eBay. I could not get it to boot from the 40MB hard drive (I did make sure the BIOS settings are correct). But booting from MS DOS 3.3 floppy, I was able to run FDISK and recognize a hard drive, even though still I could not cd to C:

I then managed to run FDISK and created a single partition - then I did FORMAT C: and formatted it.

I then did SYS C: to copy system files to the hard drive.

All these operations were successful. After this, I could cd to C: - Yay!

but, I neglected to perform additional copies of system files. My mistake.

Well when I attempt to boot from HD after reboot I get:

"Error Loading Operating System: 80"

OK fine. At this point, I again boot from DOS 3.3 floppy, my desire is to complete the process and copy files to C:. However C is unrecognizable again. When I run FDISK again to display the Partition Information, it reads much differently now with 4 partitions total - not sure how this happened ?:




Current Fixed Disk Drive: 1

Partition Status Type Start End SIze
1 A S72 367 82 q252
2 S69 100 288 189
3 S6E 357 357 1
4 S72 112 371 260

Total disk space is 614 cylinders


At this point, I can't do anything. Attempts to delete any partition (primary or extended) fail with 'No Primary DOS partition to delete', or 'No Extended DOS partition to delete'. I'm stuck, I can't reset everything and try this again? The only thing I CAN do in FDISK is change the active partition. That's it. I'm wondering if this hard disk drive is malfunctioning.

SomeGuy
December 26th, 2015, 02:59 PM
Well, what you can do is use the Norton Disk Editor or a similar tool to view the contents of the physical drive. You can then manually fill the first sector with zeros to wipe any bad partition data or other junk so you can try FDISK again. Personally I like the old lightweight Norton 4.5 NU.EXE for that kind of job. In "absolute sector" mode it doesn't care if the drive is partitioned at all, it just goes by what BIOS can read or write.

Technically it looks like that is an IDE drive, so a tool like MAXLLF might also zero the contents of the drive, but I'd consult the manual for the specific model of drive first. IDE drives that early might get confused by low-level format attempts. (Later ones just zero everything, which is still quite useful)

twqwctf
December 26th, 2015, 03:13 PM
Hi Thanks - will Norton Disk Editor be able to 'see' the HD even though I cannot cd to it? Just checking.

modem7
December 26th, 2015, 03:40 PM
Hi Thanks - will Norton Disk Editor be able to 'see' the HD even though I cannot cd to it? Just checking.
Yes (when asked to view 'physical' sectors).

Another way of zeroing the first sector is to perform the 'Step 2 - Zero data in first sector' section at [here (http://www.minuszerodegrees.net/ibm_xebec/ibm_xebec_llf_debug.htm)].

SomeGuy
December 26th, 2015, 03:50 PM
Yes, that is the idea. It will show you the raw content of the drive a sector at a time, just as it is presented by the BIOS. Since FDISK is not complaining about "no hard disk found", the computer is able to talk with the drive at the BIOS level.

It does sometimes happen that odd data in the Master Boot Record (the first sector on a hard disk) can cause FDISK to get confused and fail. When that happens, FDISK will not remove the faulty partition data itself requiring, at minimum, wiping the MBR.

But the good news is that is a software problem, not a hardware problem.

After clearing the MBR sector you should be able to run FDISK again, format a partition, and with any luck it won't go nuts a second time.

And another thought, if it does go nuts again, you might try partitioning and formatting the drive using DOS 6.22. As long as each partition is less than 32mb it should be visible to DOS 3.3. Then perform the final step of running SYS C: under DOS 3.3.

twqwctf
December 26th, 2015, 04:12 PM
OK I am using Disk Editor Version 7.0 (Symantec Corporation) and I was able to select to show physical drives. Here is what it is showing.28532

Stone
December 26th, 2015, 04:18 PM
You should consider the possibility that the drive might be hosed. Inconsistent drive stability is often an indicator of this.

modem7
December 26th, 2015, 05:11 PM
OK I am using Disk Editor Version 7.0 (Symantec Corporation) and I was able to select to show physical drives. Here is what it is showing.
Showing the first sector of the hard drive, the "MBR" (master boot record) that SomeGuy referred to. A section of the MBR contains the partition table.

So, per what SomeGuy wrote, zero all bytes in the MBR, then retry the FDISK and FORMAT operations.

SomeGuy
December 26th, 2015, 05:19 PM
That could be a boot sector virus.

Zero it out, re-FDISK, format, and let us know if it comes back.

twqwctf
December 26th, 2015, 05:34 PM
Yes I am having success with the zero out of the 1st sector. You guys really helped me big time..

wesleyfurr
December 26th, 2015, 06:06 PM
A trick I used to use "back in the day" was to use a debug script to flush the partitions (such as in the case of an NTFS or non-DOS partition that fdisk wouldn't remove). Here's the MS KB:

https://support.microsoft.com/en-us/kb/106419

And here are the steps for archival purposes in case that web page ever disappears:

Table 1: Debug Script to Erase Hard-Disk Partition Table
----------------------------------------------------------------
Debug Enter Debug Comments
Prompts Commands
----------------------------------------------------------------
- A 100 Assemble from CS:0100.

nnnn:0100 INT 13 Call interrupt 13.

nnnn:0102 press the (nnnn in the segment address).
ENTER key

- RAX Replace AX register.

AX 0000

: 0301 Write on sector.

- RBX Replace BX register.

BX 0000

: 0200 Start from ES:200.

- F 200 L 200 0 We want to write zeros.

- RCX Replace CX register.

CX 0000

: 0001 Cylinder, 0, sector 1.

- RDX Replace DX register.

DX 0000

: 0080 First physical hard disk, head
0. (Substitute 0081 for this
entry if you are clearing the
table on the second physical
hard disk, 0082 if you are
clearing the third physical
hard disk, and so forth).

- P Proceed (Debug will display
several lines of information).

- Q Quit Debug.

Stone
December 26th, 2015, 06:14 PM
I have a small Trojan executable that wipes out partitions quite nicely. :-) Each time you run it it deletes the first partition it finds. So if you run it twice it eats partition #1 and #2.

Chuck(G)
December 26th, 2015, 06:58 PM
IIRC, there were cases in DOS where if the hard disk partition table was sufficiently hosed, you couldn't boot DOS from floppy, as DOS checking the hard disk would collapse.

I have a floppy with a boot sector that wipes out the first sector on a hard disk for just that purpose. loads the code at 0000:7C00. I can UL it if you'd like.

yuhong
December 27th, 2015, 11:17 PM
I think PC DOS 7 at least improved the situation.