![]() Upper Memory Areaįor the remaining 384 KB of the first 1 MB, the upper memory area (UMA) was dedicated to hardware functions such as the video adapter, system BIOS, and peripherals. It also only supported running in real mode. The IBM XT PC and a number of PC compatibles used the Intel 8088 processor that could support up to 1 MB of RAM due to limitations of the 20-bit address bus. Back in the early 1980s, the first 64 to 256 KB of memory could be found on the motherboard directly, with the use of an expansion card to extend the size. Programs initially could only consume this space, though over time with additional device drivers in memory and so forth it became more troublesome. Despite the technological advancements over the years, the same logic applies since the original IBM XT PC in 1981.Ĭonventional memory is the first 640 KB of memory that was instantly accessible by DOS to be used for running programs. I’m sure some of you know in great detail how this works, but for those that don’t know or have forgotten over the years, the next part is a basic explanation of the different memory components.īased on the x86 architecture, there became four sections as it were in relation to memory as shown in the diagram below. Note that it’s easy to cause issues with DOS upon start up just from a typo that may cause hardware not to function for instance, so it doesn’t hurt to create a backup copy of these files before making any changes.īefore we get into the actual files itself, it helps to understand at least a basic understanding of memory. ![]() Usually on Drive C or boot floppy disks, both of these files are located on your start up disk at the root directory (i.e. When you knew you had overall 8 or 16 of MB RAM in those days thinking you had plenty, let’s just say it had its moments of frustration due to TSR (Terminate and Stay Resident) programs and so forth.įortunately we don’t need to worry about now, but I think the flip side to that was that it felt like an accomplishment when you had your PC well configured at a time when using a computer wasn’t common knowledge like it is today and with ever increasing automation.įor those running MS-DOS in some form, this is a quick reference guide to both of these files, and what many of the more common commands meant. Sometimes careful placement of commands were needed to maximise the 640 KB of conventional memory to avoid “out of memory” errors for Windows applications and games. ![]() Many of those that used MS-DOS in its heyday, would remember spending time on these two files – AUTOEXEC.BAT and CONFIG.SYS to optimise and configure their PC as needed. ![]()
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