53
votes
Why did "protected-mode MS-DOS" never happen?
16-bit protected mode DOS did sort of happen: Concurrent DOS 286 and FlexOS 286 were able to run some DOS applications in protected mode (this involved complex LOADALL shenanigans and revealed bugs in ...
- 118k
19
votes
Why did "protected-mode MS-DOS" never happen?
And, marketing-wise, did everyone want multitasking and GUI so much that an idea of a single-tasked OS was no longer appealing by definition?
In a word, yes.
The 80386 came to market in 86/87, well ...
- 4,776
14
votes
Why did "protected-mode MS-DOS" never happen?
The programs that you already had and needed to run were not protected mode programs, they needed to be run in 16-bit real mode anyway.
DOS drivers used BIOS for I/O, which also was 16-bit real mode ...
- 28.3k
14
votes
Accepted
Detecting if a video mode is supported by INT 0x10
Indeed, in many sources, the int10h subfunction AH=0 to set video mode returns without any meaningful status.
One way, suggested by C&T BIOS programming guide, is to verify if the mode is set via ...
- 28.3k
13
votes
Detecting if a video mode is supported by INT 0x10
That's not how you designed your programs in the early days of the PC:
You rather decided for one (maybe two) video cards (typically CGA and/or Hercules Monochrome) and then looked up your ...
- 33k
8
votes
Rufus FreeDOS option for CF is not bootable
Since you can't boot a FreeDOS install floppy on the target machine, you can make a disk image, and mount/use it with identical geometry in a virtual machine, and then install the OS in the virtual ...
- 28.3k
8
votes
Detecting if a video mode is supported by INT 0x10
BIOS has the ReturnFunctionalityStateInformation function 1Bh that can be used to retrieve a 20-bit bitmap of the supported video modes. You supply a far pointer to a 64-byte buffer that BIOS will ...
- 1,043
7
votes
Why did "protected-mode MS-DOS" never happen?
There was at least one proposal for a 32-bit OS that would have been a drop-in replacement for MSDOS: Marc Perkel's NovOS, submitted to Novell in 1991. The intention was that existing MS-DOS programs ...
- 6,925
6
votes
How does POST memory test work on a relatively modern (2000s) PC? Does it still test every single byte like on older ones?
Because dynamic RAM's switch-on contents is random, the memory of a computer needs to be brought to a defined state anyways. The clearing (and clear-check afterwards) is and was also the method of ...
- 33k
6
votes
Why did "protected-mode MS-DOS" never happen?
There were several attempts to introduce an ABI like this, including VCPI (Virtual Control Program Interface) and DPMS (DOS Protected-Mode Services), but the one that came closest to being a standard ...
- 8,549
5
votes
Need help restoring the OS of an "AST Premium Exec 386SX/20" laptop
I have not been able to find any official settings for the hard disk
geometry that this laptop expects to see on the IDE hard drive.
A few days ago I acquired a Toshiba T1800 386SX laptop with the ...
- 6,635
5
votes
Why did "protected-mode MS-DOS" never happen?
In a nutshell: because at that time everybody wanted GUI and multitasking.
In the other answers to this question, clever people have listed plenty of technical reasons why it would have been very ...
- 665
5
votes
Why did some BIOSes have the timer tick wrap around at 1800B1h instead of at 1800B0h?
In short, it might be for avoiding the same value for copyright reasons, or simply because some BIOS vendors calculated the value with a timer frequency value that has more precision than what IBM ...
- 28.3k
4
votes
Detecting if a video mode is supported by INT 0x10
There's a big list of video modes available, but how can I be sure that the video mode I want to set is supported?
There is no easy way - unless you can determinate what kind of Card it is. For new ...
- 213k
4
votes
Why is there only one PS/2 port on my computer?
The IBM PC and its successors the XT and AT used a 5-pin din connector for the keyboard. On the XT and AT this was the only external connector placed directly on the motherboard (the original PC also ...
- 2,634
3
votes
Why is there only one PS/2 port on my computer?
Fun fact: the PS/2 standard had a specific mouse and keyboard slot. I know because I once had the namesake IBM PS/2 computer that first used it.
I had to move the computer one day and I put everything ...
- 423
3
votes
Disable motherboard floppy controller DOS
You have already identified the Super I/O chip, and found the datasheet.
The datasheet describes on p. 80 how to get into "extended function mode", which is needed to access the control ...
- 26k
3
votes
Why did "protected-mode MS-DOS" never happen?
There was multitasking DOS called Wendin DOS constructed with their Wendin Operating System Toolkit (OST.)
The toolkit internally appeared to me to be inspired by VMS.
To get around the non-rentrant ...
- 31
2
votes
Accepted
Rufus FreeDOS option for CF is not bootable
For those who are interested, there is another way to solve this problem:
use 86Box (x86 Emulation), add a harddrive and set it to a maximum of 504MB (PreSet selection), insert the boot image of ...
- 267
1
vote
Accepted
Have I Screwed the CMOS by Booting With the Clear Jumper Set?
No, I'm just an idiot who didn't go back and check his assumptions. Maybe this will happen to somebody else, hopefully not. In the end I ordered a spare motherboard off eBay (relatively cheap, so not ...
- 2,144
1
vote
Why did some BIOSes have the timer tick wrap around at 1800B1h instead of at 1800B0h?
Maybe some points to considere:
Was this a wide-spread phenomena for which one should take precautions when creating algorithms that convert the tick count into the corresponding time, so as to avoid ...
- 213k
Only top scored, non community-wiki answers of a minimum length are eligible