On Thu, 31 Jul 2025 at 02:40, tsiegel--- via Freedos-user <freedos-user@lists.sourceforge.net> wrote: > > The NEC V20 chip didn't have the whole 286 command set, but it > apparently had enough of it that *some* 286 specific programs would work.
I never tried it myself, but the most famous example of this was the Windows 3.0 VGA driver. MS assumed anyone with a VGA card had at least a 286 so the driver used 80286 instructions, even though it ran in Real Mode. So you can't use VGA mode on an XT class machine in Windows 3.0. CGA, Hercules and EGA were fine but the VGA driver needed a 286. If you installed the driver, Windows failed to launch with an error. Unless you installed a NEC N20 (in place of an 8088) or V30 (in place of an 8086). This ran the extra 286 opcodes _in real mode_ and so suddenly Windows 3.0 in Real Mode could use VGA and you got 640*480 in 16 colours. This was quite widely documented at the time. https://www.seasip.info/AmstradXT/v30cpu.html -- Liam Proven ~ Profile: https://about.me/liamproven ~ LinkedIn/X/FB: lproven Email: lpro...@cix.co.uk ~ Google: lpro...@gmail.com IoM: (+44) 7624 227612: UK: (+44) 7939-087884 Czech [+ WhatsApp/Telegram/Signal]: (+420) 702-829-053 _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
