chandoni@husc9.harvard.edu (A Potential Security Problem) (05/19/91)
Both of these questions refer to a '386SX running DOS 4.01, but probably pertain to other systems also. Question 1: I've heard that 3.5" low density disks can be formatted to 1.44Mb if a hole is cut in them or if the drive is jumpered; Is there a means of doing this with software? Standard format programs come back with "Track 0 bad." Is there a format program (say, on simtel) which will do this? Are there any side effects? Question 2: Is there a way to boot from drive B: (on my system, a 3.5" drive) without switching the hardware? I'd like to keep my 5.25" drive as A:, but still boot the occasional 3.5" disk... there must be some obvious way to do this, but I have no idea. Thanks, JMC --- -- chandoni@husc9.harvard.edu | I will not yell fire in a crowded classroom John-Marc Chandonia | I will not yell fire in a crowded classroom Graduate Biophysics Program | I will not yell fire in a crowded classroom Harvard University | I will not yell fire ...
sasgig@unx.sas.com (Greg Grimes) (05/21/91)
In an article, chandoni@husc9.harvard.edu (A Potential Security Problem) writes: > >Question 2: > Is there a way to boot from drive B: (on my system, a >3.5" drive) without switching the hardware? I'd like to >keep my 5.25" drive as A:, but still boot the occasional >3.5" disk... there must be some obvious way to do this, >but I have no idea. PC/Computing magazine threw this question out to readers last July and there were at least two answers: (1) pull the skin off and swap floppy cables (making A: B: and vice versa), or (2) there is actually some software that does this you can buy. Didn't say how. My guess is that it scrambles BIOS' ideas as to which floppy is which during the boot process. Personally I think (1) is the simplest, but if you want to know more details about (2), I could go look it up if somebody else doesn't answer first :-). -- Greg Grimes | "Sit down, please. There are a thousand questions I'd AIX Host Development | like to ask you." -- Prof. Jacob Barnhardt to Klaatu sasgig@unx.sas.com | ("The Day the Earth Stood Still")
gurganus@stable.ecn.purdue.edu (James P Gurganus) (05/21/91)
sasgig@unx.sas.com (Greg Grimes) writes: >In an article, chandoni@husc9.harvard.edu (A Potential Security Problem) writes: >> >>Question 2: >> Is there a way to boot from drive B: (on my system, a >>3.5" drive) without switching the hardware? I'd like to >>keep my 5.25" drive as A:, but still boot the occasional >>3.5" disk... there must be some obvious way to do this, >>but I have no idea. >PC/Computing magazine threw this question out to readers last July >and there were at least two answers: (1) pull the skin off and swap >floppy cables (making A: B: and vice versa), or (2) there is actually >some software that does this you can buy. Didn't say how. My guess >is that it scrambles BIOS' ideas as to which floppy is which during >the boot process. >Personally I think (1) is the simplest, but if you want to know more >details about (2), I could go look it up if somebody else doesn't >answer first :-). I have a short program called BOOTB and all it (I think) does is put some information on the boot sector of a floppy that you stick in your normal boot drive. The code tells the computer to get the rest of its boot code from drive B. Supposedly, its as simple as that, although I've never used it (and I'm not even sure I've still got it.) I found it on a local BBS where I used to live, so I'm pretty sure its not commercial. If I remember correctly, the documentation for it said it would work for most software that followed normal DOS stuff (and I really have no idea what that means.) =) James Gurganus (gurganus@ecn.purdue.edu)
sasgig@unx.sas.com (Greg Grimes) (05/21/91)
In another article, gurganus@stable.ecn.purdue.edu (James P Gurganus) writes: >sasgig@unx.sas.com (Greg Grimes) writes: >>In an article, chandoni@husc9.harvard.edu (A Potential Security Problem) writes: >>> >>>Question 2: >>> Is there a way to boot from drive B: (on my system, a >>>3.5" drive) without switching the hardware? ... > >>PC/Computing magazine threw this question out to readers last July >>and there were at least two answers: (1) pull the skin off and swap >>floppy cables (making A: B: and vice versa), or (2) there is actually >>some software that does this you can buy. Didn't say how. My guess >>is that it scrambles BIOS' ideas as to which floppy is which during >>the boot process. > >I have a short program called BOOTB and all it (I think) does is put some >information on the boot sector of a floppy that you stick in your normal boot >drive. The code tells the computer to get the rest of its boot code from >drive B. Supposedly, its as simple as that, although I've never used it (and >I'm not even sure I've still got it.) I found it on a local BBS where I used >to live, so I'm pretty sure its not commercial. >If I remember correctly, the documentation for it said it would work for most >software that followed normal DOS stuff (and I really have no idea what that >means.) =) > >James Gurganus (gurganus@ecn.purdue.edu) I wrote something similar (also called it BOOTB :-), that read the boot sector from drive B: and executed it. Didn't work because normal DOS boot sector programs are hard-coded to read from A: (ROM BIOS read gets a 0 in DL). There's a spot in the boot sector (it's different for different versions of DOS) that contains the code that gets splatted in DL. This is changed to 0x80 for hard disks. I changed this byte to a 1 to make the boot program read from B:. Still didn't work. I gave up at that point. If you ever try BOOTB (the one you got from the BBS :-) and it works, I'd really like to know how. If you send me a copy I'll disassemble it and report. Try it first, though, I don't think it'll work because the problem's in the boot code on the B: drive, not the BOOTB code in the A: drive :-) -- Greg Grimes | "Sit down, please. There are a thousand questions I'd AIX Host Development | like to ask you." -- Prof. Jacob Barnhardt to Klaatu sasgig@unx.sas.com | ("The Day the Earth Stood Still")