Document 1301 Basic Memory Optimization Description: System Memory Optimization Because the DR DOS 6.0 operating system has been designed to work with all IBM-compatible personal computers and software applications, there is no single perfect memory setup that will optimize memory use for all situations. Memory optimization will depend both on your particular hardware setup and the software applications you will be using. However, with a bit of trial-and-error system fine tuning, you can optimize DR DOS memory management to meet your particular needs. Below are techniques and suggestions that will help you optimize your computer/software setup. Changing Order of Memory Allocation The first step in optimizing your system memory can be as simple as rearranging the order in which memory blocks are assigned by the config.sys and autoexec.bat files. The general rule here is to use upper memory and high memory as much as possible to free conventional memory for your applications. With this in mind, you should typically use HIBUFFERS and relocate the DR DOS kernel code to high memory by using the /BDOS=FFFF option of the DR DOS memory management drivers, HIDOS.SYS and EMM386.SYS. Also, if you have any add-on cards that use RAM, make sure that they are configured so that their RAM is allocated from the beginning or end of upper memory. For example, place a network card immediately above the video RAM area instead of in the middle of upper memory. Following this, device drivers and TSRs can be loaded into upper memory. For best memory allocation, those drivers and TSRs that occupy the largest blocks of memory should be loaded first and contiguously. For example, if you need to load three device drivers and two TSR programs, order them in descending order in your config.sys file, beginning with the driver that will occupy the most RAM, to the driver or TSR that will occupy the least RAM. The documentation for the drivers and TSRs should indicate the amount of RAM they require; however, if they do not, you can determine this yourself by using the following procedure: 1. Load the driver or TSR. 2. Use the MEM /U or /B command to see a report of your memory usage (see Chapter 10 of the DR DOS 6.0 User Guide for a full description of the MEM command and Chapter 12 regarding loading device drivers and TSRs). Expanding Files If, after determining the size of your drivers and TSRs and loading them into high memory, a driver or program fails to run properly or produces an out of memory error message, the problem might be that the driver or program is expanding itself in RAM. Some device drivers and TSR programs occupy a minimal amount of RAM after they are loaded into memory, but, while initializing, might actually expand and take up considerably more RAM than they will ultimately need. Another method of verifying the program's true RAM size is to load it into conventional memory (i.e., by deactivating the HIDEVICE, HIINSTALL, or HILOAD commands), activate the program, and then run the MEM /B command to see the actual amount of RAM the program occupies. If the program or driver is expanding itself in RAM, and you want to load it into upper memory, you will have to allow sufficient upper memory RAM to accommodate the initialization size of the program. It might be necessary to use trial-and-error to determine this size. See also "Using MemoryMAX with NetWare" on page 33 for an example. Example In the following example, let's assume you want to load Device Drivers 1, 2, and 3, and TSR programs 1 and 2, each requiring the following amounts of memory: Driver #1 = 13Kbyte of RAM Driver #2 = 10Kbyte of RAM Driver #3 = 16Kbyte of RAM TSR #1 = 4Kbyte of RAM TSR #2 = 6Kbyte of RAM Using the MemoryMAX HIDEVICE and/or HIINSTALL commands, enter these lines into your config.sys file: HIDEVICE = C:\DRIVER#3.SYS ; which uses 16kb RAM HIDEVICE = C:\DRIVER#1.SYS ; which uses 13kb RAM HIDEVICE = C:\DRIVER#2.SYS ; which uses 10kb RAM HIINSTALL = TSR#2 ; which uses 6kb RAM HIINSTALL = TSR#1 ; which uses 4kb RAM Note: There can be exceptions to loading TSRs and drivers in the "largest first" system described previously. Some device drivers must be loaded in a specific order. Read the manufacturer's documentation carefully before installing any driver. Note that in the above example, you can load the two TSRs with the HILOAD command placed in the autoexec.bat file. For a discussion of the MemoryMAX HIINSTALL, HIDEVICE, and HILOAD commands, see "MemoryMAX System Commands and Drivers" on page 4 in the DR DOS 6.0 User Guide. LIM Page Frame Some applications run better with the availability of LIM memory (sometimes called EMS, or expanded memory). The documentation for each of your applications will indicate if LIM memory is required. If the application does not require LIM memory, be sure that no LIM page frame is defined. This will save 64 Kbytes of upper memory. In the EMM386.SYS line of your config.sys file, disable the page frame with the switch /F=NONE. If using HIDOS.SYS on a machine with a LIM 4.0 memory card, you can disable the page frame by specifying /CHIPSET=EMSALL.