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Troubleshooting Stealth ROM This QEMM 7 technote is an abridged version of a technical bulletin that is available through our standard support channels. The information contained in this version pertains ONLY to QEMM version 7.0. If you need information relating to earlier versions of QEMM you can obtain the unabridged version from the following sources: Quarterdeck Technical Support BBS: STEALTH.TEC CompuServe: STEALT.ZIP Q/FAX: #205 Subject: Stealth ROM may seem mysterious, but it really is not. This technote tells you how to diagnose and solve problems related to the use of the Stealth ROM feature of QEMM. This document tells you how to diagnose and solve problems related to the use of the Stealth ROM feature. Please review the information in PRODUCTS.TEC before beginning the steps outlined in this technote. This technote contains information on various hardware and software products that require specific excludes or other parameters when used with Stealth ROM, and you may find the information you need here. If you are reading this technote because QEMM displayed the message "CANNOT FIND ROM HANDLER FOR INTERRUPT XX" you should instead refer to technote XSTI.TEC which was installed in your QEMM\TECHNOTE directory at the time you installed QEMM. A SIDE NOTE: QEMM's Stealth ROM feature only relocates those 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 an Analysis procedure (explained in Chapter 9 of the QEMM manual). Then use the INCLUDE parameter to include the addresses (see Chapter 7 of the QEMM manual). SECTION ONE STEP ONE: 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. Reboot your computer and 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. STEP TWO: If Stealth ROM is involved in the problem, add 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 THREE; if it does not, go on to SECTION TWO. STEP THREE: 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 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 The portions of the address space with the O in them are being accessed directly. Some program or piece of hardware is trying to read the contents of the ROM here directly, rather than accessing them through interrupts. This portion of the address space must be allowed to be accessed directly. This is done by using an EXCLUDE statement to prevent QEMM from mapping memory into this area. In our example the target region is FE00-FFFF. The 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 you only 8K of High RAM. STEP FOUR: If XST=F000 solves your problem while X=F000-FFFF does not, try using ST:F instead of ST:M. You may end up with more High RAM with ST:F than with ST:M and XST=F000. SECTION TWO PLEASE NOTE: This section is ONLY for users with video ROM. Hercules-compatible monochrome and CGA systems do not have video ROM; therefore, this section does not apply to users with such systems. On most systems, the Video ROM is located at C000-C7FF and uses 32K of upper memory address space. Some machines have a video ROM elsewhere, usually E000-E7FF. If this is true of your system, you should use E000 (or wherever your video ROM begins) instead of C000. IBM PS/2 Micro Channel machines and other Micro Channel machines have their video ROM at E000-EFFF; when using the XST parameter on such a machine, you would use XST=E000 when performing the steps outlined in this section. See the instructions in STEP NINE for the proper use of the XST=E000 parameter on a Micro Channel machine. STEP FIVE: 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 STEP THREE. If XST=C000 does work, go on to STEP SIX. STEP SIX: If XST=C000 solves the problem, try placing the Page Frame at C000. 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, this may be an acceptable solution. All the address space in which High RAM can be created is being used in this configuration. If this step does not work (or if you cannot put the Page Frame at C000) go on to STEP SEVEN: 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) which tells QEMM to allow the video ROM's own code to be used. By default QEMM replaces some of the video ROM's code with its own video code. This 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. (You may choose to try STEP EIGHT as an alternative.) If this step does not work, go on to STEP EIGHT. STEP EIGHT: 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 this 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 STEP NINE: On some machines there are other ROMs that can be Stealthed; often these are disk ROMs. The same procedure would be used for troubleshooting a disk-related problem. 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 !!00 with the beginning and ending addresses of the ROM) to determine whether the problem is related to Stealthing or to the fact that some portion of the ROM's address space needs to be directly accessible. The trick of making the Page Frame begin at the beginning of the disk ROM may also work here as well. If XST=??00 solves your problem, try replacing it with FR=??00 (as long as there is a 64K portion of the address space free beginning at ??00 and that ?? is a multiple of 16.) 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. Because of the way the ROMs are written for the IBM PS/2 machines and, perhaps, other Micro Channel machines, it is necessary to load HOOKROM.SYS before QEMM386.SYS in the CONFIG.SYS for XST=E000 to work. For example: DEVICE=C:\QEMM\HOOKROM.SYS DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M XST=E000 STEP TEN: 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. STEP ELEVEN: If ST:M with XST on all Stealthed ROMs fails, add the following parameters to the QEMM line we used in STEP TEN: 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 further in the longer, unabridged version of this technote as well as in your QEMM manual. STEP TWELVE: 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) overlain by the Page Frame. STEP THIRTEEN: If none of these steps solves the problem, Quarterdeck's Testing and Compatibility Department want 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. ADDITIONAL INFORMATION ABOUT STEALTH ROM AND RELATED ISSUES: 1) WHAT ARE ADVANCED DISK FEATURES AND VHI:N? The BIOS has a set of function calls intended for use by multitasking programs. These are Int 15, functions 90 and 91. The system ROM or disk ROM may issue the Int 15, fn 90 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 15, Fn 91, signaling the multitasking program that the disk information is ready to be processed by the system or disk ROM. 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. Whereas these caches 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 the BIOS uses the Page Frame itself (as does Stealth ROM), this could generate conflicts and system failures. Since no known disk cache does the proper Page Frame preservation, QEMM automatically suppresses INT 15, function 90 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 has these "Advanced Features" and does not save and restore the Page Frame you will crash or corrupt data on the cached drive(s). 2) CAN I LOAD A DRIVER THAT USES ROM BEFORE QEMM? You can load a device driver that uses a ROM before QEMM and still Stealth that ROM by loading the driver HOOKROM.SYS before you load this driver. HOOKROM is installed in your QEMM 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:\????????.SYS DEVICE=C:\QEMM\QEMM386.SYS RAM ST:M 3) WHY DOES XST=E000 ONLY WORK ON PS/2 MACHINES IF I USE HOOKROM.SYS? The code in the E000-EFFF portion of the ROM on PS/2 (and perhaps other Micro Channel machines) is not directly pointed to by the interrupt table. The interrupt table points to addresses in F000-FFFF, which then point to the appropriate code in the E000- EFFF segment. You can see this in the FirstMeg/ Interrupts section of Manifest. When you load HOOKROM.SYS, it traces down the redirection of the interrupts to the place where the executing code begins, so that interrupts that are serviced by code in the E000-EFFF segment actually point to addresses in the E000-EFFF segment. The use of HOOKROM.SYS is discussed in STEP NINE of the troubleshooting section of this technote. 4) WHY DOES MY COMPUTER'S SETUP PROGRAM NOT COME UP WHEN ST:M IS ENABLED? Some machines have a built-in System Setup program in the BIOS ROM that can be popped up at any time. Using Stealth ROM might 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. SUMMARY: The Stealth ROM technology has been exhaustively tested; however, due to the wide variety of software and hardware in the PC world, it cannot be guaranteed to work with every configuration. The actual Stealthing of interrupts is very successful. The most common failures are due to programs (or other ROMs) trying to access a portion of the ROM directly, rather than by means of interrupt. If you are interested in a longer, highly technical explanation of Stealth ROM, read the unabridged version of this technical bulletin, available through our standard support channels. See CONTACT.TEC in your QEMM\TECHNOTE directory for information on obtaining technotes. 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. **************************************************************** This technical note may be copied and distributed freely as long as it is distributed in its entirety and it is not distributed for profit. Copyright (C) 1991-3 by Quarterdeck Office Systems ******************* E N D O F F I L E **********************