DOS and the 640K Memory Barrier!
Though actually, there was no such barrier, if it were not for the original PC BIOS implementation.
Using some trickery it's possible to have more than 640K, way more, upto 960K.
Upper Memory Blocks, you say? Nah, that works only on 386 or better CPUs.
This video explains a long lost technique how to make use of the upper memory, end redicate it as conventional memory on 8086/8088 and machines.
And pushing the bar even further, on 286, you can combine that with the HMA, to have even more free conventional memory.
00:00 Intro
00:38 The Theory: Bumping DOS beyond 640K
06:08 About PCs with more than 640K real memory
08:03 CONFRAM revisited: Making it work!
15:18 Pushing the RAM limit to 960K
19:25 Compatible with DR DOS?
19:52 Conclusion / Outro
Links:
CONFRAM and JENSEITS (BEYOND), by c't:
c‘t 5'88, p164
https://archive.org/details/ct-1988.01/C%27t%20-%201988.05/page/164/mode/2up
c‘t 11‘88, P140
https://archive.org/details/ct-1988.01/C%27t%20-%201988.11/page/140/mode/1up
Classic Computing Forum (german):
https://forum.classic-computing.de/forum/index.php?thread/14464-confram-jenseits-upper-ram-auf-xts-nutzen/&postID=155575
TPC's Github Project for "BEYOND":
https://github.com/gpdm/TPC-jenseits-beyond
Technical References:
https://en.wikipedia.org/wiki/DOS_memory_management
https://en.wikipedia.org/wiki/Conventional_memory
https://en.wikipedia.org/wiki/Upper_memory_area
https://en.wikipedia.org/wiki/High_memory_area
https://en.wikipedia.org/wiki/Protected_mode
https://en.wikipedia.org/wiki/Intel_8086
https://en.wikipedia.org/wiki/Intel_8088
https://en.wikipedia.org/wiki/Intel_80286
https://en.wikipedia.org/wiki/I386
https://en.wikipedia.org/wiki/IBM_Personal_Computer
https://en.wikipedia.org/wiki/IBM_Personal_Computer_XT
IBM 5150 Technical Reference: https://www.minuszerodegrees.net/manuals/IBM_5150_Technical_Reference_6025005_AUG81.pdf
https://en.wikipedia.org/wiki/List_of_IBM_PS/2_models
https://en.wikipedia.org/wiki/Compaq_Portable_III
PCs without 640k barrier:
https://retrocomputing.stackexchange.com/questions/7817/who-set-the-640k-limit/7818#7818
Tim Paterson on DOS limit:
https://dosmandrivel.blogspot.com/2007/11/first-dos-machine.html
Computer Chronicles: Losing Memory (1995)
https://www.youtube.com/watch?v=YxM-sHRJh3E
Visit also THE PHINTAGE COLLECTOR website at https://www.thephintagecollector.ch for insights into my retro computer collection.
Copyright @ 2024 THE PHINTAGE COLLECTOR, Gianpaolo Del Matto. All rights reserved.
Featuring Music with kind permission by rootkitty: "Digital Aurora"
https://soundcloud.com/rootkitty
Theme Music composed by Abdallah El-Ghannam.
https://www.fiverr.com/abdallahghannam