The 1MB (also known as 640k) barrier

Very recently, PC users are running into problems when they install 4GB or more memory in their systems. If they did not use a 64-bit version of Windows XP or Vista, only about 3GB of the installed RAM would be recognised (the other ~1GB is reserved). This is due to 32-bit OSes being unable to access more than 4GB of RAM.

Back in the 1980s (not sure which year), many PC users would have encoundtered a similar headache with the 640KB memory barrier.

In which year did the 640KB barrier become a significant problem for most PC users? What was it like? Were there concerns of backward compatibilty with 16-bit applications when software/OSes for the 80386 (or 80286) was written? (just like 64-bit OSes having backward compatibility issues today)

I would appreciate it if long-time PC users can mention their experiences with the 640KB barrier.

wow, that is so cool!

sorry, I cannot help you. I just wanted to say that I never knew about this problem, or even thought about it!

Good read. I would still like to hear from some more "experienced" (old) overclockers and see how it compares to the current transition.

For me, the 640k barrier became a problem in the early 90s with DOS games. I remember the main problem was with trying to free up as much Conventional RAM as possible for certain games such as the Wing Commander I & II, and Falcon 3.0. These games needed almost 600k of free Conventional RAM to run with full sound effects and music, and it was not always easy when you also had to load a mouse driver, CD-ROM driver, MSCDEX, and sound card driver. Even though these TSRs and drivers were all about 30k or less each, then you add in EMM386 to give EMS for those Origin games, it really added up quickly.

Certain drivers and TSRs could load into the Upper memory blocks, but not always so and it could be a pain with having to arrange your CONFIG.SYS statements in a certain order. Sometimes you didn't have a large enough UMB to cram your mouse driver or MSCDEX into. If you opted to run Smartdrive, that took up even more precious RAM. DOS 5's "DOS=HIGH" statement made things a little easier. Microsoft bundled a memory optimizer called Memmaker with DOS 6 that helped make things a little easier. It was alright but it didn't do its job nearly as well as Quarterdeck's software, I had my best results with freeing up conventional RAM using QEMM386.

The helpful thing is those days were boot floppies, put your COMMAND.COM, IO.SYS, MSDOS.SYS, and your drivers onto a single floppy along with CONFIG.SYS/AUTOEXEC.BAT customized for maximum free conventional RAM for whatever game you wanted to play. A lot of games recommended this method when you wanted to play.

A lot of times I would just give up on using a mouse with a certain game, or I would copy all of the games files from the CD onto my hard drive and then edit the game config file to look to my hard drive for its data files; that alone could free up a significant chunk of Conventional and Upper memory, sometimes it made the difference in being able to play Wing Commander II with full music and speech (and it was quite a treat hearing the Emperor and Prince Thrakhath speak in the intro video!)

Some later DOS games such as Raptor completely ignored the 640k barrier and looked at your total XMS instead, making it much much easier to play.

My favourite tool in memory management at that time -> Quarterdeck QEMM386 !