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EXPANSION BOX REFERENCE MANUAL Published by Rupp Corporation Copyright (C) 1989 by Sewell Development Corporation Expansion Box is a set of programs that allow one IBM compatible PC to use the disks and printers of another IBM compatible PC. This document describes the various device driver and TSR modules of Expansion Box. Note: Expansion Box and FastLynx are independent programs. FastLynx does not require Expansion Box nor does Expansion Box require FastLynx. However, it is possible to use FastLynx in "Local Copy" mode with the Expansion Box device drivers. The basic idea behind Expansion Box is to let one PC use another PC as an expansion box. The communication between the two PCs is accomplished with the high speed serial and parallel protocols developed for FastLynx (Fastwire II). The FastLynx program transmits files quickly between two computers. However, in many environments it is convenient to use two computers as if they are one computer. Expansion Box lets the disks and printers of one computer be accessed directly by another. Thus application programs can access information on both computers simultaneously. Regular DOS commands can use files on both computers and printing can be done by either computer (or both). A program like Expansion Box is possible because of a powerful feature of the MS-DOS operating system--known as installable device drivers. Device drivers are part of the operating system. They perform communication between a device--such as a disk or printer--and the rest of the computer. In some cases the device is in the same box as the rest of the computer (for example a disk or internal modem). In other cases the device is separate from the computer and communication is performed through a communication port and cable (such as a printer). In either case, the device driver is the software that controls the communication to the device. Expansion Box device drivers are no different from regular device drivers. Communication occurs on a serial or parallel cable and the controlled device is another computer. The computer with the device drivers is called the lead or master computer. The controlled computer is called the server or slave computer. You may have noted that these device drivers are "installable". Unfortunately, this means that they must be installed. The EBOX program has a quick and easy installation option. The installation option modifies your CONFIG.SYS and AUTOEXEC.BAT files. To start the installation process, connect both computers with either a serial or parallel FastLynx cable and start the EBOX program on both computers. On the lead computer (you must decide which should be the lead computer) press Enter and follow the given instructions. It's likely that you will need no further information about the installation process. However, some environments require a different setup than the installation option provides. To handle these situations, an explanation of the device driver options and features follows. If you have any problems or suggestions, please give us a call! EXPANSION BOX FILES There are seven files in the Expansion Box program. They are: 1) EBOX.EXE The server program. Execute this program on the server computer when you want Expansion Box to be active. EBOX handles requests from the device drivers on the lead computer. Also, EBOX has options to install the device drivers, to change the current drive assignments and print mode, and to un-install the device drivers. 2) EBOX.HLP The help screens for the EBOX.EXE program. 3) README.BOX This file. 4) EBOXPAR.SYS The main Expansion Box device driver for parallel communication. This device driver contains all the code needed to use the disk drives of the server computer using a parallel communication protocol. 5) EBOXSER.SYS The main Expansion Box device driver for serial communication. This device driver contains all code needed to use the disk drives of the server computer using a serial communication protocol. 6) EBOXCHAR.SYS An auxiliary Expansion Box device driver for additional character devices. This device driver contains all the code needed to use character devices on the server computer. Usually this would be a printer, but it could also be used for COM ports or even the server's clock. 7) EBOXPRN.COM A TSR (Terminate and Stay Resident) program used for redirecting BIOS level printing. EBOX.EXE and EBOX.HLP are the only files required on the server computer. All others are used only on the lead system. The EBOX.EXE program must be executing on the server system with the FastLynx cable connected for the lead system to be able to access the drives and devices of the server. If EBOX is not executing or the cable is not connected, a drive or device not ready error will be issued. Main Block Device Drivers EBOXSER.SYS and EBOXPAR.SYS EBOXSER.SYS and EBOXPAR.SYS perform the same function. The only difference between the two drivers is the communication protocol used. EBOXSER.SYS uses serial communication and EBOXPAR.SYS uses parallel communication. The installation process will determine which FastLynx cable you connected and install the correct driver for that cable. The installation process also performs three other important services for these drivers: First, it sets the ports on which communication can take place. It sets the device drivers port list to EBOX's port list. The parallel driver ignores serial ports, likewise the serial driver ignores parallel ports. Normally the port list is "LPT*,COM*", and communication can occur on all valid ports. To have the program automatically select the port that is connected to the other computer is a great convenience. However, you can select a specific or non-standard port (or set of ports). See the help screen to the port list configuration for more details. Second, the installation process sets up the default drive assignments. Each drive on the server computer that you want to use from the lead computer must be assigned a drive letter. Unfortunately, the drive letter on the server system is usually being used by some other drive on the lead system. For example: if you want to use the server's drive A:, it needs to be assigned a drive letter on the lead system. It would be nice to use the same drive letter, but A: is already assigned to the lead computer's floppy disk so another drive letter, such as D: or E:, must be assigned. It is possible to assign any currently unused letter to the drive. However, MS-DOS assigns drive letters sequentially. If you assign a drive to the letter Z:, all other drive letters (for instance letters between E: and Y:) will be unavailable for use other than within EBOX. Also, each unused drive letter can require up to 200 bytes of resident memory! Attempts to use unassigned drive letters will result in the lead system issuing an invalid unit number error. The installation option will display a warning if this condition can occur. The drive letter assignments are probably the most difficult part of the Expansion Box programs to understand and use. It is often difficult to remember which drive letters you have assigned to server drives. You can examine the current drive assignments by choosing the "Change drive assignments" option of the EBOX program. This option also allows you to change the current drive assignments. One mnemonically useful way to set up the drive assignments is to assign the server systems floppy drive to F: and its hard disk to H:. The last service performed by the installation option is for serial drivers only. The installation will set the baud rate of the serial driver to the baud rate used at installation time. Some computers cannot use the highest baud rate (notably the PS-2 Model-80). If you are having problems with serial communication, run the FastLynx diagnostic option to determine a safe baud rate. There are some options for block device drivers that are not available through the installation process. To use these options, install the device driver normally. After installing the drivers, you can edit your CONFIG.SYS file to take advantage of these options. After you have edited the CONFIG.SYS file, you will need to re-boot the computer to make the options effective. The syntax for the device line in the CONFIG.SYS file is as follows: DEVICE=[path\]EBOXPAR.SYS [/Rdddd] [/Ssignature] [/A] for parallel communication or DEVICE=[path\]EBOXSER.SYS [/Rdddd] [/Ssignature] [/A] for serial communication (fields in [] are optional). /Rdddd Specifies a maximum wait time for receive timeouts in seconds. /Ssignature Specifies a unique signature for this device driver. /A Specifies Auto Configuration Mode. Some types of devices are unusually slow in responding to requests made by the device driver. Normally the device driver makes a request and waits for a response from the server system. The maximum time that the device driver will wait is specified with the /R option. Example: /R60 tells the device driver to wait one minute before timing out. The default value is 20 seconds. This is more than necessary for all hard disks, floppy disks, ram disks, etc. However, once in a while a longer timeout is needed. A case where a longer timeout would be needed is when a tape drive is being used to emulate a disk drive and the rewind time takes too long. The /S switch is used to give this device driver a unique identity. This is useful for hooking up multiple server computers to one lead computer. A later section explains the use of this option. In some environments it is useful to have the drive assignments set up according to information received at boot time. The following actions will take place when the /A option is used and communication is established at boot time. 1) The number of logical drives installed will be the number of logical drives on the server system. 2) The drive assignments will begin at the first available drive letter and proceed sequentially--one for each drive on the server. If communication is not established at boot time, the /A option has no effect. After booting, the drive assignments can be changed in the normal manner. This option is most useful when you are using one computer to hook up to several different server computers at different times. However, its usefulness is limited because you must reboot every time you hook up to a different computer. If you do not reboot when you hook up to another computer, you will receive a server mismatch error. Expansion Box forces this error to avoid problems with the computer's disk cache. BIOS Level Print Redirector EBOXPRN.COM Printing can be sent to the server computer at two levels. One method is to install a character device driver for the printer. This method will be described in the next section. Another method is to trap the print requests at the BIOS level. There are several advantages to trapping print requests at the BIOS level. First, many applications use BIOS level printing rather than DOS level printing. Also, the Print Screen keys (PrtSc and Ctrl/P) use BIOS level printing. The standard LPT device drivers simply call the BIOS to perform the actual printing, so trapping the print requests at the device driver level is not really necessary. The EBOXPRN.COM TSR performs BIOS level print redirection. The installation process will place a command in AUTOEXEC.BAT to load this TSR. If you do not desire printing to be redirected, remove the line from AUTOEXEC.BAT. EBOXPRN requires that one of the Expansion Box block drivers be loaded. If a main block driver is not found, an error message will be displayed and EBOXPRN will not install itself. If EBOXPRN has already been loaded, it does not reload itself, but simply changes the current options. The command line is: eboxprn [/Ssignature] [/Mm] [/Pls[ls[ls]]] The /Ssignature option identifies a particular main Expansion Box driver that contains the communication protocol. This option is described in a later section. The /P switch specifies a port mapping table. Each ls pair contains a mapping for a single BIOS port. Both the l and the s must be between 1 and 3 inclusive. The l specifies the line printer number on the lead system (1 for LPT1, 2 for LPT2, ...) and the s is the line printer number on the server system to which the print from the lead printer is to be sent. If the /P is specified, all ports not specifically mentioned, will not be redirected. Examples: /P12 redirects lead printer LPT1 to server printer LPT2 and does not redirect LPT2 or LPT3. /P1222 redirects both LPT1 and LPT2 to the server's LPT2. LPT3 is not redirected. If no /P switch is found when the TSR is loaded, /P112233 is assumed. The /Mm defines the current printing mode. M can be one of R, L, or A. R Remote mode. When in remote mode, all print requests will be sent to the server system. If the server printer is not on- line or the server system is not connected (or not running EBOX), a printer off line error code will be returned to the lead system. L Local mode. When in local mode, print requests are not sent to the server computer. No port mappings are done. This mode essentially turns off all print redirection. A Autoswitch mode. This mode attempts to print on the server computer. However, if the server printer is not on-line, an attempt will be made to do the printing on the lead computer. Essentially, this mode attempts to find which computer has an on-line printer, and sends the print request to that printer. The print mode can be changed by either the EBOXPRN command or by using the Change Print Mode option in the EBOX program. The port mapping table can only be changed with the EBOXPRN command. Character Device Drivers EBOXCHAR.SYS There are two kinds of device drivers--block and character. Block devices are devices which have files stored on them--such as disks, or floppy disks. Character devices are non-file devices used for input or output--such as printers, keyboards, or mice. Accesses to block devices are made through drive letters such as A: or C:. Accesses to character devices are made through a name such as COM1 or LPT2. The EBOXPAR.SYS and EBOXSER.SYS device drivers are block drivers. With one of those device drivers, you can get access to all of the block devices on the server computer. EBOXCHAR.SYS is a character driver with which you can gain access to a single character driver on the server system. The installation program does not install this driver for you. If you wish to use one of the server system's character devices, you will need to add the following DEVICE= line to your CONFIG.SYS file: DEVICE=[path\]eboxchar.sys /Nname /Rserver_name [/Ssignature] The signature option and path are optional. However you must specify both the lead name (/N) and the server name (/R). These options are described below: The /Ssignature option is used to identify the particular main Expansion Box driver that contains the communication protocol. This will be described in a later section. Note, an Expansion Box block device driver must be loaded before any character device drivers. The /Nname option specifies the character device name on the lead system. This can be from one to eight of the valid filename characters. If this name is the same as a device driver that already exists on the lead system, then the previous driver will be superceded by this device driver. The /Rserver_name specifies the character device name on the server system. This device name must be an already existing device driver on the server system. If it does not exist, you will be given an error message if you attempt to use the device. Like the lead name, this name can be from one to eight valid filename characters. Examples: DEVICE=EBOXCHAR.SYS /NLASER /RLPT2 This device line adds a new device LASER to the lead system. Output requests made to the device LASER will be sent to the server system's LPT2. DEVICE=EBOXCHAR.SYS /NPRN /RPRN This device line replaces the lead systems PRN device with the remote systems PRN device. Output that would normally go to the PRN device on the lead computer will be sent to the PRN device on the server computer. Normally this would not be needed as the BIOS level redirection (EBOXPRN.COM) can perform the same operation. However, if you have an improved print spooler, it may be useful to redirect the print at the device driver level rather than the BIOS level to take advantage of the spooler's better print buffering. DEVICE=EBOXCHAR.SYS /NCOM2 /RCOM1 DEVICE=EBOXCHAR.SYS /NREMPRN /RPRN The above example adds two device drivers to the lead system. Note that both device drivers use the same driver file. The first line replaces the lead system's COM2 with the remote system's COM1 device. Input and output requests on COM2 will be redirected from/to the server system's COM1. The second line adds a new device REMPRN to the lead computer. It will send output to the server computer's PRN device. (Note, there is a difference between the device PRN and LPT1--the difference is the name--but DOS thinks that the two are different devices). Any character device driver can be superceded by an Expansion Box device (except the NUL device). This includes devices such as CLOCK$ and CON. However, overriding the CON device (the keyboard and screen) will most likely not yield the expected results. Too many programs skip the device driver levels and write directly to the screen or read directly from the keyboard at the BIOS or hardware level. If you want to experiment with the CON device we STRONGLY!! recommend that you test the process from a bootable floppy disk before installing the device driver on you hard disk! Installing More than One Expansion Box It is possible to have multiple servers attached to a single lead computer. The main block drivers do all of the actual communication. The character device drivers and the TSR look for the presence of a main block driver and use the protocol routines within the main driver for communication to the server computer. This is done to save (a lot of) resident memory. However, it causes problems when multiple block drivers are installed; an auxiliary driver or TSR will not know which main driver to use. To solve this problem all Expansion Box device drivers, TSRs and the EBOX program itself take a command line argument /Ssignature. When the auxiliary driver or TSR is loaded, it looks for the main driver with the matching signature. If a main driver with the same signature is not found, an error will be reported and the device driver will not be installed. The signature can be from one to eight valid filename characters. To change drive mappings or print modes when multiple drivers are installed, the EBOX.EXE program also takes a /Ssignature option on the command line. Note that if you misspell the signature, the EBOX program will not find the main driver you were looking for and think that no drivers are installed. If this happens, simply exit and try again. One other problem can occur when trying to install multiple Expansion Boxes. If you have additional FastLynx parallel or serial cables, you may want to use the same communication protocol to talk to both server computers. The problem is that the device drivers for both server computers would have the same name (either EBOXSER.SYS or EBOXPAR.SYS). The port list and drive assignments tables are part of the driver itself, so you cannot use the same device driver file for both servers. One solution to this problem is to install the first driver, rename the device driver and change the DEVICE= line in CONFIG.SYS appropriately, then install the second driver (with a different port list, signature, and drive assignment tables). You should completely install the first driver (including the re-boot) before attempting to install a second one. Partitions Larger than 32MB and 12-bit vs 16-bit FATs Expansion Box correctly handles partitions larger that 32MB on IBM DOS 4.0, Compaq DOS 3.31, and Zenith DOS 3.30 PLUS. The method to handle large partitions for DOS 4.0 is slightly different than the method used by DOS 3.31 and DOS 3.30+. However, Expansion Box detects this condition and adjusts accordingly. That is, it is possible to have a DOS 4.0 system for one computer and a DOS 3.31 or DOS 3.30+ system for the other, both with large partitions. Due to the evolving nature of MS-DOS, there are certain errors that can occur when the lead computer is running a DOS version previous to the DOS version on the server. These conditions are given below. Please note, it is always possible to reverse the roles of the computers to avoid these problems. DOS 2.xx cannot access a DOS 3.xx or 4.xx disk if the FAT (File Allocation Table) entries are 16-bits. DOS 2.xx can only access 12-bit FATs. DOS 3.0 and greater can access both 12-bit and 16-bit FATs. Attempts by a lead system running DOS 2.xx to access a server disk drive that has a 16-bit FAT will result in a NON-DOS disk error (which can only be aborted). DOS versions previous to DOS 3.31 cannot access partitions larger than 32MB. An attempt by a lead computer running a DOS version previous to DOS 3.31 to access a partition larger that 32MB will result in a NON-DOS disk error. There are several products on the market that modify DOS to be able to access partitions larger than 32MB (previous to DOS 3.31). To use Expansion Box with these products, both computers must be running the same modified DOS version. Attempts to access partitions larger than 32MB by DOS versions that are not modified in the same manner will result in a NON-DOS disk error. Generally these products work by using a sector size larger than 512 bytes. Expansion Box looks for sector size incompatibility and issues errors and warnings appropriately. You can also hook multiple computers up in a chain. However, the performance will not be as good as if the server computers are hooked up directly to the lead. In this case the computers in the middle of the chain are acting as both lead and server simultaneously. Optional Device Driver Features Starting with DOS 3.0 there are several optional features for device drivers. The Expansion Box block drivers support all of these optional features except IOCTL and GENERIC IOCTL (which include get and set logical device). Since Generic IOCTL is not supported, you will not be able to format disks through the Expansion Box drivers. The only feature not supported in the Expansion Box character drivers is GENERIC IOCTL. Not supporting the Generic IOCTL feature means that setting alternate character sets for character devices cannot be done though the Expansion Box. Note that the normal IOCTL is support (since it is often used to control printers and modems). Also note: attempts to access Expansion Box devices through the BIOS will not work (except BIOS printing which is handled by EBOXPRN.COM).