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Troubleshooting Stealth ROM Quarterdeck Technical Note #205 Filename: STEALTH.TEC by Quarterdeck Testing & Compatibility CompuServe: STEALT.ZIP Last revised: 4/02/95 Category: QEMM Subject: Troubleshooting and resolving rare problems with Stealth ROM, and extensive information on how Stealth ROM works. Stealth ROM may seem mysterious and cryptic, but it really is not. This note tells you how to diagnose and solve problems related to the Stealth ROM feature of QEMM. Although this note may appear lengthy, it is detailed and informative. For those who are more interested in fast solutions, the path to resolving a problem is quite straightfoward and quick. Q. What do I need to know first? Before beginning the steps outlined in this technote, please review the information in Quarterdeck Technical Note #248, "Product Compatibility Information" (PRODUCTS.TEC), which contains information on various hardware and software products that may require specific treatment with Stealth ROM. This bulletin can be found in your QEMM\TECHNOTE directory. If you are reading this technote because QEMM displayed the message "Disabling Stealth ROM becauase QEMM cannot find the ROM handler for INT xx", you should instead refer to Quarterdeck Technical Note #233, "QEMM and the XSTI Parameter" (XSTI.TEC). This note can also be found in your QEMM\TECHNOTE directory. You may also wish to consult Quarterdeck Technical Note #168, "QEMM's Stealth ROM Technology" (STLTECH.TEC") for background information on Stealth ROM and how it works. Q. How do I resolve a conflict with Stealth ROM? In almost all cases, the OPTIMIZE program that comes with QEMM will detect and resolve automatically any aspect of your system's hardware or basic configuration that is incompatible with Stealth. OPTIMIZE cannot, however, anticipate the behaviour of programs that are not run as part of your CONFIG.SYS, AUTOEXEC.BAT, or other batch files that are CALLed as part of your system's startup process. The following troubleshooting procedure is divided into simple steps, contained in several sections, to address compatibility issues with programs that are not run as part of the startup process, or that manage to evade OPTIMIZE's automatic handling of Stealth ROM. SECTION ONE 1) The first step is to ascertain whether Stealth ROM is involved with the problem. Remove the Stealth ROM parameter (ST:M or ST:F) from the QEMM device line in your CONFIG.SYS file and rerun Optimize. When Optimize completes, try to duplicate the problem. If the problem still happens, then Stealth ROM is not causing the problem, and you should refer to the troubleshooting section of your QEMM manual for further information. However, if removing ST:M or ST:F solves the problem, proceed to Step 2. 2) Now that we have proven that Stealth ROM is involved in the problem, add the Stealth ROM parameters ST:M and XST=F000 to the QEMM device line in the CONFIG.SYS file. Your QEMM line would look something like this: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M XST=F000 Reboot the computer. If this step solves the problem, go on to Step 3 immediately below; if it does not, go to SECTION TWO. 3) If XST=F000 solves your problem replace this parameter with X=F000-FFFF, reboot your computer, and try again to create the problem. The QEMM line in your CONFIG.SYS file would look something like this: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M X=F000-FFFF If the problem persists, go to Step 4 below. If you cannot recreate the problem with the above line, add the parameter FSTC to the end of the line as follows: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M X=F000-FFFF FSTC and reboot. If this step solves the problem, continue on. If it does not (and FSTC may not work in all circumstances) then remove the FSTC parameter and reboot with the previous QEMM line. In either case, run Manifest (by typing MFT from the DOS prompt) and look at the QEMM/Analysis screen. The last line should look something like this: Fn00 IIII IIII IIII IIOO Since the entire F000-FFFF range is EXCLUDEd, Analysis here is suggesting that the last two 4K pages of the F region are Okay (that is, the EXCLUDE is appropriate for the region FE00-FFFF) and that the other pages are INCLUDEable (that is, the EXCLUDE is not needed for these pages). This is so because some program or piece of hardware is trying to read the contents of the last two pages of ROM directly, rather than accessing them through interrupts. QEMM must be prevented from mapping High RAM over this ROM to allow the ROM to be be accessed directly. This is done by using the EXCLUDE parameter. In our example the target region is FE00-FFFF; thus appropriate EXCLUDE is X=FE00-FFFF and the QEMM line would look like this: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M X=FE00-FFFF This EXCLUDE allows Stealth ROM to do its job and costs only 8K of High RAM. If you are at this point, your problem is solved and you do not need to continue with this technical note. 4) If XST=F000 solves your problem while X=F000-FFFF does not, try changing ST:M to ST:F, and remove XST=F000. You may end up with more High RAM with ST:F than with ST:M and XST=F000. However, if ST:F fails, remove ST:F and place ST:M and XST=F000 back on the QEMM386.SYS line. SECTION TWO This section is ONLY for systems that have video ROMs--that is, systems with an EGA or VGA video card. CGA color and Hercules-compatible monochrome systems do not have video ROM; If you have one of these systems, proceed to Section Three. Manifest, on its First Meg Overview screen will identify the ROMs on your system when Stealth ROM is inactive. On most systems, the Video ROM is located at C000-C7FF and uses 32K of upper memory address space. Some machines (particularly Micro Channel machines such as the IBM PS/2 family) have a video ROM elsewhere, generally at E000. If this is true of your system, you should use E000 (or wherever your video ROM begins) instead of C000 in the QEMM386.SYS lines that follow. 5) If XST=F000 does not solve your problem, try XST=C000. The QEMM line of the CONFIG.SYS would look like this: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M XST=C000 If XST=C000 does not work, go on to Section Three. If XST=C000 does work, proceed to Step 6 immediately below. 6) If XST=C000 solves the problem, try placing the page frame at C000 by removing XST=C000 and adding FR=C000 to the QEMM386.SYS line. Do this only if the entire C000 range is available--that is, no device is using address space between C000 and CFFF for Adapter ROM or RAM. The QEMM line of the CONFIG.SYS would look like this: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M FR=C000 If this works, you may find this an acceptable solution. All the address space in which High RAM can be created is being used in this configuration, and you will want to stop troubleshooting here. If this step does not work (or if you cannot put the page frame at C000) go on to Step 7 below. 7) If XST=C000 solves the problem but you do not want to put the page frame at C000 (or cannot for some reason) then try the parameter F10:N (or FASTINT10:N). By default QEMM uses its own code for some video functions, rather than the video ROM's own code. The F10:N parameter tells QEMM not to perform this function. The QEMM line of the CONFIG.SYS would look like this: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M F10:N If this step works, all ROMs are being Stealthed at the expense of some speed. You may find this satisfactory, at which point you may stop here. If you do not find the modest decrease in speed acceptable, or if this step does not work, proceed to Step 8 immediately below. 8) If XST=C000 solves the problem but FR=C000 or FASTINT10:N does not (or you either cannot put the Page Frame at C000 or do not want to use FASTINT10:N) then replace XST=C000 with X=C000-C7FF. The QEMM line of the config.sys would look like this: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M X=C000-C7FF If replacing the XST=C000 parameter with X=C000-C7FF does not work then you should replace the X=C000-C7FF with XST=C000, which will avoid all Stealth conflicts with your system's video ROMs; you may stop troubleshooting here. If replacing the XST=C000 parameter with X=C000-C7FF works, add the parameter FSTC to the QEMM line: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M X=C000-C7FF FSTC Reboot your computer. If this step works, continue on; if this step does not work (and FSTC may not work in all circumstances) then remove the FSTC parameter and reboot with the previous QEMM line. In either case, run Manifest (by typing MFT at the DOS prompt) and look at the QEMM/Analysis screen. The Cn00 line should look something like this: Cn00 OIII IIII OOOO OOOO This indicates that the first 4K region of the C000 range (in the video ROM) is being accessed directly. This portion of the address space must be EXCLUDED from QEMM's use when Stealth ROM is enabled. The appropriate QEMM line in the CONFIG.SYS would be: DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M X=C000-C0FF SECTION THREE 9) On some machines there are other ROMs that can be Stealthed. Typically these are disk ROMs; sometimes they are associated with network cards or with other peripherals. To determine if your system has one of these other ROMs, boot your system without ST:M or ST:F and check the First Meg / Overview screen in Manifest. If you see more than two ROMs listed, than your system has another ROM. Troubleshooting Stealth ROM with these ROMs involves a similar procedure to those above; that is, add XST=??00 (using the beginning address of that particular ROM). If this solves the problem, replace the XST=??00 with the appropriate EXCLUDE (X=??00-!!FF, replacing ??00 and !!FF with the beginning and ending addresses of the ROM) to determine whether the problem is related to Stealth or to the fact that some portion of the ROM's address space needs to be directly accessible. If some portion of the address space must be EXCLUDED for Stealth ROM to work you should check Analysis with the FSTC and X=??00-!!FF parameters on the QEMM line in a manner similar to that detailed in Step 3. The trick of placing the page frame at the beginning of the ROM may also work here as well. If XST=??00 solves your problem, try replacing it with FR=??00. This is possible if there is a 64K portion of the address space that is either ROM or RAM beginning at ??00, and if ?? is a multiple of 16K. 10) Use XST=F000, XST=C000, and XST=??00 simultaneously for all ROMs being Stealthed. Then replace the XSTs one by one with the appropriate regular Exclude (X=F000-FFFF, X=C000-C7FF, X=??00- !!FF...) and look at the QEMM/ Analysis screen of Manifest to see what portions of the address space need to be directly available. 11) If ST:M with XST on all Stealthed ROMs fails, add the following parameters to the QEMM line we used in Step 10: FB:N UFP:N VHI:N F10:N If this works, remove the XSTs one at a time to determine which one(s) you actually need. If an XST alone does not solve the problem, turn back to SECTION ONE for help in determining the appropriate XST or EXCLUDE while keeping the above parameters. The parameters are explained later in this technote as well as in your QEMM manual. 12) If ST:M does not work, try ST:F instead. If ST:F does not work, try ST:F XST=C000 (and XST=??00) for Stealthed ROMs other than the one(s) the page frame overlays. 13) If none of these steps solves the problem, Quarterdeck's Testing and Compatibility Department wants to know what program or device is failing (and at what point). Please contact our Technical Support staff so that our technicians can get all the necessary information about your problem. The following section contains questions and answers on various aspects of Stealth and its parameters. Again, you may wish to consult Quarterdeck Technical Note #168, "QEMM's Stealth ROM Technology" (STLTECH.TEC") for background information on Stealth ROM and how it works. Q. I have a ROM that is not being turned in High RAM by Stealth ROM. Why? A. QEMM's Stealth ROM feature relocates ROMs which are accessed through the use of interrupts. A ROM that is not Stealthed may still have regions that are never used during the system's normal operation. Some disk ROMs, video ROMs, and devices that only use their ROMs during bootup (before the CONFIG.SYS is loaded) fit into this category. You may be able to get more High RAM by INCLUDING these unused regions on the QEMM386.SYS device driver line in CONFIG.SYS. To find out what addresses you can include, run the Analysis procedure, then use the INCLUDE parameter to include these addresses. Refer to your QEMM manual for further information on Analysis. Q. What is FASTINT10:N? A. When Stealthing a video ROM, QEMM replaces some of the video ROM's routines with code written by Quarterdeck. This replacement code is suitable for almost all video cards. The FASTINT10:N parameter (which may be abbreviated F10:N) tells QEMM not to use its code but the code of the video ROM instead. This in no way limits the amount of High RAM Stealth ROM creates and may be an acceptable solution for those users who need it. It should only be necessary on unusual video cards. If placing the page frame at the beginning of the video card's ROM works or if a small regular exclude also solves the problem you may choose to use F10:N instead. Q. What is FSTC? A. In addition to program code, ROMs contain various tables of information. A ROM may itself access these tables directly. When the ROM is being Stealthed normally, Stealth ROM will prevent direct access to the ROM by copying various tables into QEMM's own data area, which uses some extra memory -- usually in High RAM. When a ROM is being Stealthed but the address in which the ROM resides is EXCLUDEd (as with X=C000-C7FF), QEMM cleverly figures out that it does not need to make copies of these tables in its own data area. QEMM therefore saves memory by not making copies of the tables. However, if the copy is not made, portions of the ROM where these tables are stored will be accessed directly. This will cause Analysis to report that a portion of the address space is OK when EXCLUDED even though it would not be accessed directly were it not EXCLUDED. FSTC (which stands for ForceStealthTableCopy) makes the Analysis procedure accurate by forcing QEMM to make copies of these tables so that inappropriate EXCLUDEs are not recommended. Some system and video ROMs may not function properly with the FSTC parameter. If this is the case on your system you will have to perform the Analysis procedure without the FSTC parameter. However, you should be aware in this case that some of the EXCLUDE statements that Analysis prompts you to use may not be necessary. You can try reducing these EXCLUDES on a trial-and-error basis if you wish. FSTC should only be used when you are testing a portion of a ROM's address space for direct access by excluding the whole ROM. It is not an appropriate parameter for a final configuration. Q. What is FB:N? FB:N, short for FRAMEBUF:N, disables QEMM's feature of breaking up disk reads into the page frame and disk writes from the page frame. FB:Y is the default with Stealth ROM; FB:N is the default without Stealth ROM. Q. What is UFP:N? A. When Stealth ROM is active, and when no program is using expanded memory, QEMM unmaps the memory left in the page frame. This allows the ROM underneath the page frame to be visible, in case some program reads that ROM directly. However some programs use expanded memory and then free an EMS handle (which is tantamount to ceasing to use that expanded memory) and yet expect the page frame to contain the memory that they last mapped there. The UFP:N (abbreviation for UNMAPFREEPAGES) parameter tells QEMM not to unmap the EMS page, which will make such programs work with Stealth ROM. Of course such programs violate the EMS specification by abandoning the EMS handle (and apparently common sense) but expecting the page frame to contain the memory just released. UFP:N is the default without Stealth ROM. Q. What are advanced disk features? What is VHI:N? A. The BIOS has a set of function calls intended for use by multitasking programs. These are INT 15h, functions 90h and 91h. The system ROM or disk ROM may issue the INT 15h, Fn 90h call while it is waiting for the disk controller to read or write a sector, allowing other programs to execute during this wait. When the sector is ready, the disk interrupt handler issues an INT 15h, Fn 91h, signalling the multitasking program that the disk information is ready to be processed by the system or disk ROM. The "advanced features" of some disk caches hook this call to allow your system to go ahead and execute your current program while the system or disk ROM is waiting for its requested sector. Although such caches properly preserve the stack and register state for the BIOS and the application when doing this pseudo-multitasking, they do not preserve the mapping of the page frame. Therefore, if a BIOS call causes the page frame to be used (as is the case with Stealth ROM active), conflicts and system failures could result. Since most disk caches do not preserve the page frame properly, QEMM automatically suppresses INT 15h, Fn 90h calls from the BIOS, effectively disabling advanced disk features. Caches that save and restore the page frame when using advanced disk features can use a programming interface to QEMM to re-enable advanced disk features. You may defeat QEMM's defeating of this feature with the VIRTUALHDIRQ:N (VHI:N) parameter on the QEMM device line in your CONFIG.SYS file. If your cache uses INT 15h Fn 90h as one of its advanced features, and does not save and restore the page frame you will crash or corrupt data on the cached drive(s). Q. Can I load a driver that uses ROM before QEMM? A. You can load a device driver that uses a ROM before QEMM and still Stealth that ROM by loading the driver HOOKROM.SYS (found in your QEMM directory) before you load this driver. directory. Here is an example of a CONFIG.SYS file that loads HOOKROM, then a driver that uses a ROM, then QEMM with Stealth ROM enabled: DEVICE=C:\QEMM\HOOKROM.SYS DEVICE=C:\DISK\ROMDRIVER.SYS DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M For a more detailed explanation of HOOKROM, refer to XSTI.TEC in your QEMM\TECHNOTE directory. Q. Why does my computer's BIOS Setup program fail when I use ST:M? A. Many machines have a built-in System Setup program in the BIOS ROM that can be popped up via a keystroke. Stealth ROM may make this feature inaccessible to you after your system has booted. Because the Setup program accesses the ROM directly, you must EXCLUDE the portion of address space where it is stored in order for it to work after QEMM has been loaded and Stealth ROM enabled. On most machines this Setup program is found in F000- F7FF. You may decide that you would rather have access to the Setup program ONLY on bootup and use this portion of the address space for High RAM. Since you must reboot your computer after making changes in your CMOS Setup anyway, most users consider this a fair trade. Q. How does Stealth ROM work? What can cause it to fail? A. Refer to consult Quarterdeck Technical Note #168, "QEMM's Stealth ROM Technology" (STLTECH.TEC") for background information on Stealth ROM and how it works and what can interfere with it. SUMMARY: The Stealth ROM technology has been exhaustively tested. Due to the wide variety of software and hardware in the PC world, however, Stealth ROM cannot be guaranteed to work with every configuration. The actual Stealthing of interrupts is very successful. Most failures are due to programs (or other ROMs) trying to access a portion of the ROM directly rather than by means of interrupt, and most of these failures can be resolved via the techniques in this note. If you experience a problem that you are unable to resolve using the steps outlined in this technical bulletin, Quarterdeck would very much like to hear about it. ****************************************************************** * Trademarks are property of their respective owners. * * This and other technical notes may be available in updated * * forms through Quarterdeck's standard support channels. * * Copyright (C) 1995 Quarterdeck Corporation * ******************** E N D O F F I L E ***********************