Back in the day, there was a website called amihotornot.com, where people could post photos of themselves and others could vote on how good they look.
This spawned a variety of copycat sites, all using the amiXornot name template. My favourite was amibiosornot.com, which showed you a photo of a PC motherboard, and asked: AMI BIOS or not?
You can always ignore the BIOS routines and directly touch hardware registers/etc. so as long as you know precisely what hardware you are dealing with. Of course, this is what modern OSes do for most hardware after bootstrapping since calling back into BIOS isn't really an option.
BIOS routines are purely an abstraction layer, though the abstraction is somewhat leaky and my understanding is that most hardware was trying to be IBM compatible even when software skips the BIOS routines and directly touches hardware interfaces.
The thing is, as far as I know you do not need to use the video BIOS routines even to set the video mode. After all, the video BIOS routines are also just routines that run on the CPU, the only advantage they really have is that of any abstraction, the fact that using it allows you to be compatible with any card that implements that software interface even if it doesn't implement the same exact hardware interface. But as far as I know, if you know you're dealing with a VGA compatible card, you can set the mode by directly flipping around CRTC registers and it should work just fine.
However, since GPUs tended to vary widely when going beyond VGA modes (although I believe even the original VGA controller was capable of 800x600x4 with a suitably lenient autosync monitor), VESA VBE was introduced to make that much easier again.
Windows actually runs the VBIOS in an emulator / VM for switching modes with the default GPU driver.
The BIOS was an abstraction layer. In the old days, not everything was 100% IBM PC compatible. There were lots of weird graphics cards. Some systems had incompatible disk and keyboard controllers.
There was no memory protection in Real Mode, so you could always poke the hardware yourself, but something written on a Tandy wasn't going to work on a Zenith unless you supported both, or ran everything through the BIOS.
Over time, the OS took over the HAL role, with the BIOS only being used until the OS could load native drivers. Now it's UEFI... same idea with a higher greater level of abstraction and modularity.
Sounds like you lived through this, but for the younger generation...
I think the way to compare this with a modern machine is that the the early machines had no memory management or protection, meaning that any program could access any byte of memory, or any i/o address. Whether it was a good idea or not was up to the programmer.
There were BIOS and OS calls for interacting with display memory, that were supposed to make code more portable across machines. Devs almost immediately started writing to hard-coded address regions directly, which pinned those addresses down. Use of "unofficial" addresses and entry points made it phenomenally difficult to update the hardware or BIOS. This was true in the Apple ][, but also on PC's. For instance it's what created the infamous 640k memory limit.
I had an MS-DOS machine but its memory mapping was not identical to the IBM PC. Thus it was not "PC compatible." Apps that used the official MS-DOS calls worked just fine. Thankfully, two of those apps were Word Perfect and Turbo Pascal. I didn't need much else.
It was the wild west. Today, you try POKEing around where you don't belong, and you get a protection fault.
I mostly agree with all this -- I remember the glee with which people would discover and report "undocumented" BIOS or DOS interrupt calls, and the feeling that Microsoft were holding back on documenting these calls for selfish reasons -- but I can't see how they caused the 640k limit. That limit was built into the segmented memory architecture of real mode 8086 and successor CPUs.
I have the Phoenix version of this already. The Ralf Brown Interrupt List is also very relevant and vendor-neutral, as well as including some normally-undocumented stuff, if you're interested in low-level PC programming.
Phoenix CBIOS:
https://bitsavers.org/pdf/ibm/pc/ps2/bios/CBIOS_for_IBM_PS2_...
Phoenix ABIOS:
https://bitsavers.org/pdf/ibm/pc/ps2/bios/ABIOS_for_IBM_PS2_...
Back in the day, there was a website called amihotornot.com, where people could post photos of themselves and others could vote on how good they look.
This spawned a variety of copycat sites, all using the amiXornot name template. My favourite was amibiosornot.com, which showed you a photo of a PC motherboard, and asked: AMI BIOS or not?
I should know the answer to this, but was using the BIOS the only way to interact with hardware like disks, mice, and keyboard?
I remember copying code to make wrappers for those in C from books but can't remember if that was the only option or...
I know with VGA you had to use the BIOS to set modes but you could just write to the memory which was mapped at a certain address
You can always ignore the BIOS routines and directly touch hardware registers/etc. so as long as you know precisely what hardware you are dealing with. Of course, this is what modern OSes do for most hardware after bootstrapping since calling back into BIOS isn't really an option.
BIOS routines are purely an abstraction layer, though the abstraction is somewhat leaky and my understanding is that most hardware was trying to be IBM compatible even when software skips the BIOS routines and directly touches hardware interfaces.
e.g. you can see documentation for the VGA card here: https://wiki.osdev.org/VGA_Hardware
The thing is, as far as I know you do not need to use the video BIOS routines even to set the video mode. After all, the video BIOS routines are also just routines that run on the CPU, the only advantage they really have is that of any abstraction, the fact that using it allows you to be compatible with any card that implements that software interface even if it doesn't implement the same exact hardware interface. But as far as I know, if you know you're dealing with a VGA compatible card, you can set the mode by directly flipping around CRTC registers and it should work just fine.
Same for disk controllers and etc.
However, since GPUs tended to vary widely when going beyond VGA modes (although I believe even the original VGA controller was capable of 800x600x4 with a suitably lenient autosync monitor), VESA VBE was introduced to make that much easier again.
Windows actually runs the VBIOS in an emulator / VM for switching modes with the default GPU driver.
The BIOS was an abstraction layer. In the old days, not everything was 100% IBM PC compatible. There were lots of weird graphics cards. Some systems had incompatible disk and keyboard controllers.
There was no memory protection in Real Mode, so you could always poke the hardware yourself, but something written on a Tandy wasn't going to work on a Zenith unless you supported both, or ran everything through the BIOS.
Over time, the OS took over the HAL role, with the BIOS only being used until the OS could load native drivers. Now it's UEFI... same idea with a higher greater level of abstraction and modularity.
Sounds like you lived through this, but for the younger generation...
I think the way to compare this with a modern machine is that the the early machines had no memory management or protection, meaning that any program could access any byte of memory, or any i/o address. Whether it was a good idea or not was up to the programmer.
There were BIOS and OS calls for interacting with display memory, that were supposed to make code more portable across machines. Devs almost immediately started writing to hard-coded address regions directly, which pinned those addresses down. Use of "unofficial" addresses and entry points made it phenomenally difficult to update the hardware or BIOS. This was true in the Apple ][, but also on PC's. For instance it's what created the infamous 640k memory limit.
I had an MS-DOS machine but its memory mapping was not identical to the IBM PC. Thus it was not "PC compatible." Apps that used the official MS-DOS calls worked just fine. Thankfully, two of those apps were Word Perfect and Turbo Pascal. I didn't need much else.
It was the wild west. Today, you try POKEing around where you don't belong, and you get a protection fault.
I mostly agree with all this -- I remember the glee with which people would discover and report "undocumented" BIOS or DOS interrupt calls, and the feeling that Microsoft were holding back on documenting these calls for selfish reasons -- but I can't see how they caused the 640k limit. That limit was built into the segmented memory architecture of real mode 8086 and successor CPUs.
No, there were MS-DOS interrupts for those as well.
BIOS became more relevant for graphics programming as MS-DOS did not do graphics, only text mode.
These became my bibles of the time,
"PC assembly language step-by-step"
https://archive.org/details/pcassemblylangua0000hoff
"Advanced assembly language on the IBM PC"
https://archive.org/details/advancedassembly0000holz
"PC intern system programming : the encyclopedia of DOS programming know how"
https://archive.org/details/pcinternsystempr0000tisc
Last one is great, it has examples on Quick Basic, Turbo Pascal, Turbo C and C++, Microsoft C and C++, TASM and NASM.
The interrupts were used to call bios commands.
The whole DOS was only a tiiiny line between the bios. In fact, I think it really was only “DISK” os.
Edit: https://mrszeto.net/CIT/interrupts.htm
DOS only did file system operations and a few date/time calls
And since I listed all the books I used routinely I didn't know that.
Parent,
> I should know the answer to this, but was using the BIOS the only way to interact with hardware like disks, mice, and keyboard?
First link from your URL
> READ CHARACTER FROM STANDARD INPUT, WITH ECHO
Also drivers loaded via config.sys would extend MS-DOS, and be exposed via additional interrupts, e.g 0x33h for mices.
Now is interrupt 0x33h populated by MS-DOS, after loading a mouse driver configured in config.sys, still MS-DOS API or not?
you could use IO which BIOS also uses. BIOs provided basically some library or api to make it easier, and did some init of platform.
you can also program the vga outside of bios if its PCI. not sure about agp and older stuff tho as i never really got to play with it.
bios essentially is just some software running in CPL 0. it doesnt have special access or privileges.
No, you could always access the hardware directly.
I have the Phoenix version of this already. The Ralf Brown Interrupt List is also very relevant and vendor-neutral, as well as including some normally-undocumented stuff, if you're interested in low-level PC programming.
I thought this was something to do with the Amiga