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COMPUTER BITS BY GREG SWAIN Running MemMaker & avoiding memory conf licts Having trouble with General Protection Faults in Wind­ows? Try running the MemMaker memory optimisation program. This will sometimes overcome the problem and your programs will run more efficiently too. I remember seeing a movie some time ago – a Western actual­ly – in which someone gets shot. “Who would want to shoot Bad Bart?”, queried a bystander after the bullets had stopped flying and everyone had crawled out from behind the bar. “Just about every­one who ever knew him”, came the reply. What’s this got to computers and memory? Well, in this case, the question is “Who’s encountered a General Protection Fault when running Windows?” Answer: “just about everyone who’s ever used it”. OK, so it’s a bad analogy but you get the general idea – General Protection Faults in Windows are not uncommon. There you are working away happily, running lots of applications, when all of sudden up comes an error message. Often, it will read someth­ing like this: Progman caused a General Protection Fault in module File­name at 0001:0296. Now isn’t that helpful? What this means in plain English is that your Windows application has written to a memory space that was already occupied, clobbering another module (or file) in the process. As a result, the system becomes unstable and the wisest course is usually to exit all applications and reboot Windows. Now there are lots of reasons why GP faults can occur, including incompatible terminate-and-stay-resident programs (TSRs) or device drivers in your CONFIG.SYS and AUTOEX­EC. BAT files. In that case, you can often troubleshoot the problem by removing these TSRs – just type “REM: in front of the appropriate entries. If that solves the problem, you can then proceed to replace the lines one by one until the problem reappears. When it does, you’ll know which one is causing the GP fault. Often, however, GP faults are caused by other memory man­agement problems. If you consistently get the same error message when a certain function is performed, then running Mem­Maker may overcome (or at least minimise) the problem. EXTENDED MEMORY 1024K FFFF UPPER MEMORY AREA 384K 640K A000 CONVENTIONAL MEMORY AREA 640K Computer memory Before we take a look at the Mem­ Maker program, let’s first briefly look at how memory is organised in a PC. Fig.1 shows the memory configuration of a typical computer. The first 640Kb is called “conventional” mem­ory and is used by all MS-DOS programs. Above that but below 1Mb is a 384Kb block called the “upper mem­ory area”. This block is normally reserved for use by hardware expansion cards, such as your display adapt­ er, and for shadowing video ROM and the ROM BIOS. Following the upper memory area, the area beyond 1Mb is known as “extended” memory. This memory HIGH MEMORY AREA 64K 0K 0000 Fig.1: the memory configuration in a PC. The first 640Kb is called “conventional” memory, while the area from 640Kb to 1024Kb (1Mb) is the “upper memory area”. The area beyond 1Mb is known as “extended” memory. requires the use of an extended memory manager such as HIMEM. SYS and this device driver is typically loaded as the first line in your CONFIG.SYS file. Finally, the first 64Kb of extended memory is known as the “high September 1995  57 drivers and programs. On the other hand, if you run a DOS-based program that does require expanded memory, you will have to replace the NOEMS switch with the RAM switch instead. This will allow EMM386.EXE to simulate expanded memory so that the program will run. For exam­ple, the command: DEVICE=C:\DOS\EMM386.EXE 512 RAM By typing mem /c/p at the DOS prompt, you can see which programs are loaded into conventional memory and which are loaded into upper memory. It will also tell you how much free conventional memory you have and whether or not MSDOS is resident in the high memory area. memory area” (HMA). Usually, MSDOS is set to run in the HMA, to free up conventional memory for use by other programs. To see how your computer currently organises memory, exit Windows and type mem /c/p at the DOS prompt. This will show you which programs are loaded into conventional memory and which are loaded into upper memory. It does this by displaying a detailed listing of the load order and size of these programs – see Fig.2. It will also tell you how much free memory you have, the largest executable program size and whether or not MS-DOS is resident in the high memory area. What MemMaker does Because the hardware expansion cards do not use up the entire upper memory area, it contains free areas of space and these are known as “upper memory blocks” (UMBs). When you run MemMak­er, it modifies your AUTOEXEC.BAT and CONFIG.SYS files so that some TSRs and device drivers are loaded into these UMBs instead of into conventional memory. As a result, conventional memory is freed and this can make a big difference to the way your programs run. 58  Silicon Chip If you’ve already run MemMaker and subsequently installed additional software, it can also help to avoid memory management conflicts be reallocating space in the upper memory blocks. By the way, in order to load programs into the upper memory blocks, you must use an expanded memory manager such as EMM386.EXE. Depending on the entry in your CONFIG. SYS file, this device driver can also use extended memory to simulate expanded memory for those DOS-based programs that require it. Typically, the first three lines of CONFIG.SYS will look like this: DEVICE=C:\DOS\HIMEM.SYS DEVICE=C:\DOS\EMM386.EXE NOEMS DOS=HIGH,UMB Note that it is necessary to load HIMEM.SYS before EMM386.EXE to gain access to the upper memory blocks. The NOEMS switch ensures that EMM386.EXE behaves as an upper memory manager only and prevents it from allocating extended memory (EMS) for use as expanded memory (XMS). Use this switch if your programs do not require expanded memory, as this frees an additional 64Kb of upper memory for running device will allocate 512Kb of your computer’s extended memory for use as expanded memory. Note that you should only allocate as much expanded memory as the program requires and this will usually be specified in the installation manual. If the command line that loads EMM386.EXE is missing, it can easily be added by editing the CONFIG.SYS file in an ASCII text editor. Alternatively, the MemMaker program will automatically install and configure EMM­386.EXE for you. Start-up disc Before running MemMaker, it’s vital that you create a start-up disc in case anything goes wrong. To do this, install an unformatted floppy disc in drive A and type: FORMAT A:/S. This done, copy your AUTOEXEC.BAT and CONFIG.SYS files (and preferably your SYSTEM.INI file in the Windows directory) to the floppy disc. That way, if anything goes wrong, you can boot from the start up disc and simply copy the original files over the top of the modified files on the hard disc. It’s also a good idea to disable any commands in your AU­TOEXEC.BAT and CONFIG.SYS files that start unnecessary device drivers and utility programs. This will help to free up conven­ tional memory by ensuring that such programs do not compete for space in upper memory. For example, if you only use a mouse when running Windows, then you can disable any mouse device drivers such as MOUSE. COM. To disable a command, simply open the file in an ASCII text editor (eg, DOS Edit or Notepad) and insert a REM statement at the beginning of the command line, eg: REM DEVICE =C:\DOS\MOUSE. This done, save the file and then reboot the computer. By disabling the command in this manner, rather than deleting the line, you can easily restore it later on if required. Running MemMaker MemMaker is supplied with MSDOS 6.0 and above and is straightforward to run – just quit all programs, go to the com­mand prompt (ie, C:>) and type Memmaker. All you have to do then is follow the on-screen prompts or the step-by-step proce­dure set out in the manual. Unless you are an experienced user, it’s best to choose Express Setup (as opposed to Custom Setup) when running MemMaker for the first time. You should also initially answer “No” to the prompt that asks you whether you use any programs that require expanded memory, unless you are sure that the reverse is true. If you choose No and subsequently find that some programs no longer run or display error messages (eg, “Expanded Memory Unavailable”), then its simply a matter of running Mem­Maker again and answering “Yes” to the same question. After you have finished running MemMaker, take a look at your CONFIG.SYS and AUTOEXEC.BAT files. In CONFIG.SYS, you will see that MemMaker has changed certain “device” commands to “devicehigh” and added switches to those “device­high” commands. Similarly, in AUTO­EXEC. BAT, you will find that Mem­Maker has added “lh” (loadhigh) to the beginning certain commands. These “devicehigh” and “lh” commands ensure that the corre­ sponding device drivers and TSRs are loaded into the upper memory area. Note, however, that HIMEM.SYS and EMM386.EXE cannot be loaded high. Now for the acid test – to find out AUTOEXEC.BAT Before MemMaker <at>ECHO OFF VERIFY OFF PATH C:\DOS;C:\WINDOWS;C:\ALDUS;C:\PM5;C:\UTIL; C:\DESKSCAN;C:\TSCSI; SET TEMP=C:\TEMP SET DIRCMD=/P/O PROMPT $P$G C:\DOS\MOUSE C:\DOS\MSCDEX.EXE /D:PANASON /L:R C:\DOS\DOSKEY VER WIN After MemMaker <at>ECHO OFF VERIFY OFF PATH C:\DOS;C:\WINDOWS;C:\ALDUS;C:\PM5;C:\UTIL; C:\DESKSCAN;C:\TSCSI; SET TEMP=C:\TEMP SET DIRCMD=/P/O PROMPT $P$G LH /L:3,56928 C:\DOS\MOUSE LH /L:3,27984 C:\DOS\MSCDEX.EXE /D:PANASON /L:R LH /L:2,6400 C:\DOS\DOSKEY VER WIN Fig.3 (above): a typical AUTOEXEC.BAT file before and after running MemMaker. MemMaker has added “LH” commands to the start of several lines, to ensure that these TSRs are loaded into the upper memory blocks. Fig.4 (right): devices are loaded into the upper memory blocks using the DEVICEHIGH command. Note, however, that HIMEM.SYS and EMM386.EXE cannot be loaded high. what effect MemMaker has had on your system, go to the command prompt and again type mem /c/p. You should see that many (if not all) of the available device drivers and TSRs are now loaded into upper memory instead of conventional memory. In addition, you should have a corre­ sponding increase in conventional memory. Fig.3 shows a typical AUTOEX­EC. BAT file before and after running MemMaker, while Fig.4 shows typical before and after CONFIG.SYS files. If you encounter problems after running MemMaker, you can easily undo the changes that have been made. To do this, you simply go to the command prompt (ie, C:\>) and type: Memmaker /undo. By then following the on-screen prompts, the program will restore the original AUTOEX­EC. BAT, CONFIG.SYS and SYSTEM.INI files, using backups that it made during CONFIG.SYS Before MemMaker DEVICE=C:\DOS\HIMEM.SYS DEVICE=C:\DOS\EMM386.EXE NOEMS X=C800-CBFF BUFFERS=30,0 FILES=60 DOS=HIGH,UMB LASTDRIVE=Z FCBS=4,0 DEVICE=C:\TSCSI\MA348.SYS DEVICE=C:\TSCSI\TSCSI.SYS DEVICE=C:\CDMKE.SYS /D:PANASON DEVICE=C:\DOS\SETVER.EXE DEVICE=C:\DESKSCAN\SJII.SYS BREAK=ON COUNTRY=61,,C:\DOS\COUNTRY.SYS SHELL=C:\DOS\COMMAND.COM C:\DOS\ /E:1024 /p STACKS=9,256 After MemMaker DEVICE=C:\DOS\HIMEM.SYS DEVICE=C:\DOS\EMM386.EXE NOEMS X=C800-CBFF BUFFERS=30,0 FILES=60 DOS=HIGH,UMB LASTDRIVE=Z FCBS=4,0 DEVICEHIGH /L:2,9568 =C:\TSCSI\MA348.SYS DEVICEHIGH /L:2,15488 =C:\TSCSI\TSCSI.SYS DEVICEHIGH /L:2,13472 =C:\CDMKE.SYS /D:PANASON DEVICEHIGH /L:2,12048 =C:\DOS\SETVER.EXE DEVICEHIGH /L:1,7040 =C:\DESKSCAN\SJII.SYS BREAK=ON COUNTRY=61,,C:\DOS\COUNTRY.SYS SHELL=C:\DOS\COMMAND.COM C:\DOS\ /E:1024 /p STACKS=9,256 September 1995  59 Fig.6: this detailed map shows the upper memory area from A000-FFFF. The gray areas are treated as ROM and are reserved for the video card (C000C7FF) and the ROM BIOS (F000-FFFF). The areas marked with “U” indicated used UMBs, while “F” indicates free UMBs. the optimisation process. Alternatively, if you suspect that the problem might be caused by one or more commands in AUTO­EX­EC.BAT or CONFIG.SYS, you can bypas some or all of the commands in these files (MS-DOS 6.0 and above). To bypass all the commands in these two files, press the F5 key when you see the text “Starting MS-DOS . . .” while the computer is booting up. Alternatively, to bypass individual commands, press the F8 key instead and follow the on-screen prompts to carry out or bypass each command in turn. The Memmaker.sts file That’s not necessarily the end of the memory optimisation process. Often, you can free up even more memory by changing the order of the command lines in your CONFIG.SYS and AUTOEXEC.BAT files. The reason for this is that as each driver is loaded in turn into the upper memory area, it uses the largest free remain­ing UMB. This means that if the smaller drivers are loaded first, the remaining UMBs might not be able to accommodate some of the larger drivers. In this case, these remaining large device drivers will be loaded into 60  Silicon Chip conventional memory rather than upper memory, despite the presence of “devicehigh” or “lh” commands. The trick is to reorganise your CONFIG.SYS and AUTOEXEC.BAT files so that the largest device drivers are loaded first. That way, it will be easier to fit the remaining drivers into the smaller UMBs that are left over. How do you know the sizes of your device drivers? Well, when you run MemMaker for the first time, it logs this informa­tion in a file called MEMMAKER.STS (in the C:\DOS directory). Open this file in an ASCII text editor (or better still print it out) and make a note of the MaxSize line for each command in the [SizeData] section – see Fig.5. It’s now simply a matter of editing the CONFIG.SYS and AUTOEXE­C.BAT files so that those command lines with larger Max­File values are positioned Command=C:\DOS\SETVER.EXE Line=11 FinalSize=864 MaxSize=12048 FinalUpperSizes=0 MaxUpperSizes=0 ProgramType=DEVICE Fig.5: a typical section from a MEMMAKER.STS file. The MaxSize value is the one to note. above those with smaller MaxFile values (make sure that HIMEM.SYS and EMM386.EXE are before any of these, however). Save each file in turn, then reboot your comput­er to check that the system starts properly and that there are no error messages during start-up. If all is well, run MemMaker again to optimise the system for the revised CONFIG.SYS and AUTOEX­EC. BAT files. By now typing mem /c/p at the command prompt again, you can quickly check how much more conventional memory has been freed. Note, however, that the above procedure is not always hassle free. Sometimes, for example, it is necessary to load the drivers for a particular device in a set order (where more than one driver is involved). If the order is incorrect, you will get an error message during boot-up, often to the effect that a particular driver is missing. In that case, it’s usually just a matter of moving the command line for the “missing” driver ahead of its companion driver. Fig.4 shows an example of this. If you look at this file, you will see that the line DEVICEHIGH /L:2,9568 =C:\TSCSI\MA348.SYS precedes the line DEVICEHIGH /L:2,15488 =C:\TSCSI\TSCSI.SYS even though the second line has the largest MaxSize value. That’s because it’s necessary to load MA348.SYS before TSCSI.SYS for this particular device (an external cartridge drive). Fine tuning Now take a look at the detailed memory map of Fig.6. One im­portant thing to realise here is that not all addresses in the upper memory area are available for loading device drivers and TSRs. For example, the area from A000-C800 is reserved as ROM for video card addresses, while the area from F000-FFFF is reserved for shadowing the ROM BIOS. Similarly, the area from E000-EFFF is also normally a reserved area. What this means is that these ranges are out of bounds for use as UMBs unless you specifically instruct EMM386. EXE to in­clude certain areas within them (ie, EMM386.EXE does not map over unused ROM). This is done using the I= switch. For example, if your computer has a VGA or EGA monitor, you can generally include the range of address from B000-B7FF and from E000-EFFF. In this case, the EMM386 entry in your CONFIG.SYS file would look something like this: Exploring the Memory with MSD 1. To see how memory is allocated in your machine, go to the DOS prompt and type MSD. The screen shown at left will appear. Click on Memory. DEVICE=C:\DOS\EMM386.EXE I=E000-EFFF I=B000-B7FF NOEMS If you subsequently find that your monitor doesn’t respond correctly or your computer hangs when you start Windows, delete the I=B000-B7FF entry. If you still have problems, delete the I=E000-EFFF statement On the other hand, it is also often necessary to specifi­cally exclude certain address ranges to prevent memory conflicts with hardware cards. If this is not done, a device driver can be loaded into the address normally occupied by the hardware card and this will prevent the card from being found. For example, let’s say that you have a hardware card (eg, a scanner card) at address C800. In this case, you might want to exclude the range from C800-CBFF and this is done using the X= switch, ie: 2. The resulting screen shows free (F) and used (U) UMBs, plus areas which are reserved as ROM. Click the down arrow to see the area below C000. 3. Clicking “Utilities” and then “Memory Block Display” brings up this screen. You can now examine the memory allocated to each driver by clicking on it (in this case, SMARTDRV.EXE). DEVICE=C:\DOS\EMM386.EXE I=E000-EFFF I=B000-B7FF NOEMS X=C800-CBFF Note that MemMaker will normally automatically exclude the address ranges occupied by hardware cards the first time you run it. If you subsequently install another hardware card and you strike problems, try changing the address setting on the card. Alternatively, you can work through the section entitled “You Installed A Hardware Device And Your Computer Stopped Working” in chapter 8 of the MS-DOS 6 manual. By the way, it’s also a good idea to edit the Emmexclude= entry in SYSTEM.INI, to prevent Windows from accessing this address range when running in Enhanced mode – ie, add the line Emmexclude=C800-CBFF to the [386Enh] section of SYSTEM.INI. In addition, some video cards use additional memory in the region from C400-C700. Although Windows automatically detects most of these cards and avoids this area, there are cases where you have to specifically exclude it using the Emmexclude entry. For example, to avoid the area from C400-C7FF (to prevent conflict with a video card) and from C800-CBFF to prevent conflict with another hardware card, the line would read: Emm­ex­clude=C400-CBFF. If you are still having trouble running Windows in enhanced mode (eg if the system frequently crashes), try starting Windows using the “/d:x” switch – ie, type win /d:x at the command prompt. This will prevent Windows from accessing any of the upper memory area and is equivalent to adding Emmexclude=A000-EFFF to SYSTEM.INI. If this solves the problem it means that there is a con­flict with some hardware card that Windows is unable to detect. To solve this problem, you need to identify which hardware card is causing the problem and then exclude its address with Emmexclude. To find out the address, check the address switches on the card or use the Micro­ soft Diagnostics program MSD.EXE . Try to limit the excluded the range to the specific card. If Windows is unable to find enough free UMBs for what are called “translation buffers” when it loads, it uses conventional memory instead. As a result, there will be less memory available to run non-Windows applications. Finally, if it’s all too hard, consider upgrading to Windows 95. With this system, the old DOS/Windows combination is gone and you don’t have to worry about tweak­ing AUTOEX­EC. BAT, CONFIG.SYS and SYSTEM.INI files. Is your computer up to Windows 95? Here we go again! SC September 1995  61