Some chipsets have jumpers to set XMS and EMS assignment of the main memory. Virtually every AT-class or better computer has some XMS memory and nearly all users install the device driver that enables access to XMS. 386 and later CPUs feature an protected mode extension called Virtual 8086 mode that allows mimicking a 8086 memory layout for applications. The Expanded Memory Specification (EMS). DOWNLOAD HimemX 3.32 for Windows. Since UMA memory is managed in blocks the amount of free Upper Memory is usually larger than the largest contiguous free block. MS-DOS 6.2 6.21 6.22 : 3.10, recognizes max. While UMBs are a optional feature of XMS HIMEM.SYS does not support UMB. Conventional memory or base memory is the memory range between 0 kb and 640 kb. This prevents programs running in protected mode from interfering with each other's memory. Another way is to use a utility that changes the start up files such that the amount of free conventional memory is maximal (e.g. This API is implemented by a driver (such as HIMEM.SYS) or the operating system, which takes care of memory management and copying memory between conventional and extended memory, by temporarily switching the processor into protected mode. When loading himem.sys the memory is configured as XMS memory (eXtended Memory … Extended memory is a contiguous block, so you can address it much more easily than expanded … Microsoft, Lotus, Intel, and AST Research (January 1991). Expanded Memory can be either memory on an memory expansion card or a part of the main memory. I'm not sure if this WILL work coz it's been a while since I've used dosbox, but it's worth a try Good luck and keep us posted. A protected-mode operating system such as Microsoft Windows can also run real-mode programs and provide expanded memory to them. This can reduce available UMBs considerably. As rule of thumb TSRs taking more memory should be loaded before small TSRs to prevent memory fragmentation. This is usually of 16 kB size and reserved in UMA. Some TSRs do not work correctly when loaded to upper memory, resulting in crashs or erratic system behavior. enabling of UMBs and installation of APIs for XMS and EMS access. It is also helpful to know the most common memory management drivers. Rather well supported is the NEAT chipset. Ack, I have to answer my own question. On x86-based PCs, extended memory is only available with an Intel 80286 processor or higher. Extended memory referred to that memory above 1 megabyte. When using the mem /c command from a DOS window in Windows, no upper blocks are seen, as shown in the above example. This API is implemented by a driver (such as HIMEM.SYS) or the … 4 Gb, 1023 MB XMS useable. I would like to run dos 6.22 with supplemental disk (because I want the dos shell). Because of the available support for expanded memory in popular applications, device drivers were developed that emulated expanded memory using extended memory. Total: 65,967,536 Used 64,**8,960 Free 1,048,576. So what they did was leave a hole in memory between 640K and 1 MB, then put the rest of their memory up above 1 megabyte. The High Memory Area (HMA) are the 64 kb directly above 1 Mb and are part of XMS. Specifying DOS=LOW can be used to prevent DOS from using the HMA. These memory areas are referred to as the high memory area (HMA) and the upper memory area (UMA; also referred to as upper memory blocks or UMBs). 941056 bytes available XMS memory MS-DOS resident in High Memory Area mem /f. EMM386 emulates expanded memory by using main memory beyond the High Memory Area. The corresponding load statement in config.sys is DEVICEHIGH= and in autoexec.bat LOADHIGH which can be shortened to LH. I would like to run dos 6.22 with supplemental disk (because I want the dos shell).