SVGA in DOS guests would require emulating SVGA chipset

[ssybesma]

I have been tinkering with VMs of older OSes and have made successful use of SciTech Display Doctor in Windows 98SE. Works perfectly.
But I thought in order to use that, there must be a SVGA chipset present, no?

With Windows 98SE there isn't...there is just the same VBoxVGA emulation that DOS has to use.
So how does that work exactly if the SDD app detects a SVGA chipset in Windows 98SE that's not really there?

Is it a virtual SVGA chipset driver?

All this is done without Virtualbox having to do anything which is interesting, so I'm not asking VIrtualbox developers to do anything.
Specifically, what is interesting is that VBoxVGA emulation allows for greater resolutions to be displayed other than 640 x 480 (using special software like SDD) and doesn't force 640 x 480.

Once I understand that better, the next direction is to find out if there is driver that can be run in DOS that does the same thing (emulates a SVGA chipset).
Just wondering if someone knows if anyone independently developed a driver like that.
I suspect those involved with DOSBox may have a leg up on this issue since their app has built-in SVGA emulation support but I doubt there is any discrete driver that a DOS VM can use that can be pulled from their package.

My last question is what real-world video chipset the VBoxVGA emulation was based on whether it's possible to load my own video drivers into DOS that are compatible with VBoxVGA.

Thanks. Just trying to get a little bit better understanding.

[mpack]

I have been tinkering with VMs of older OSes and have made successful use of SciTech Display Doctor in Windows 98SE. Works perfectly.
But I thought in order to use that, there must be a SVGA chipset present, no?

There's a VESA chipset present. That's a generic register-level API (VESA is/was an industry standards authority). It is not specifically comformant to VGA, SVGA etc. SciTech and BearWindows are VESA compatible drivers. An equally significant standardisation impetus comes from the BIOS (mostly PS/2 compatible), which has calls to set specific graphics modes, select fonts etc, so you can be pretty sure that a graphics API of that era supports all of those modes.

[ssybesma]

Thank you for your excellent reply. So as I understand it there's no barrier to being able to achieve SVGA in a DOS VM under Virtualbox...the trick is locating a driver that emulates a virtual SVGA chipset.
That was the obstacle I ran into trying to use the SciTech Display Doctor for DOS...it reported it could not detect an SVGA chipset. However the Windows version of it apparently provides that SVGA chipset emulation for Windows 98SE (probably what 'Nucleus' is).

[mpack]

I'm not sure what you mean by "emulate a virtual SVGA chipset". As I understand it, VirtualBox is not emulating a specific (S)VGA chipset that a DOS app might test for and find. Instead it provides a VESA compatible register API, which includes support for some graphics modes which are the equivalent of SVGA graphics modes.

Also, DOS didn't have a standard driver model - each app rolled their own. So you can't expect to install a driver and hey presto all apps see it and use it. Prior to Win3, DOS provided no native graphics capabilities.