80286 Protected Mode Test

On Sun, 14 Mar 2021 at 19:37, Guy Sotomayor via cctalk <cctalk at classiccmp.org> wrote: Incidentally, I believe that OS/2 1 was not the only 286 OS affected by this. The development versions of DR's Concurrent DOS 286 could multitask DOS apps in protect mode on pre-release 286s, but Intel "fixed" the feature that permitted this in the first shipping version of the 80286, to DR's dismay and horror. https://books.google.cz/books?id=2y4EAAAAMBAJ&pg=PA17#v=onepage&q&a… AIUI the feature was later restored, but customer uncertainty, together with suddenly-questionable compatibility with all the 286s out there, killed CDOS 286. I suspect this is instrumental in why DR took FlexOS and X/GEM down the RTOS route instead... in which form it survived and a distant descendant, formerly IBM 4690 OS, is still sold by Toshiba. -- Liam Proven ? Profile: https://about.me/liamproven Email: lproven at cix.co.uk ? gMail/gTalk/gHangouts: lproven at gmail.com Twitter/Facebook/LinkedIn/Flickr: lproven ? Skype: liamproven UK: +44 7939-087884 ? ?R (+ WhatsApp/Telegram/Signal): +420 702 829 053