CP/M

home *** CD-ROM | disk | FTP | other *** search

/ CP/M / CPM_CDROM.iso / jsage / znode3 / tcj / tcj40tp.ws < prev next >

Wrap

Text File | 1994-09-02 | 15.8 KB | 358 lines

[Note from Jay Sage: When I met Terry Pinto in Portland in May, he told me about the technique he had developed to overcome the 88 Mbyte limit on the Ampro Little Board he uses to run his remote access computer system. My immediate response was, "Please write it up for TCJ!" And here it is.] 86 YOUR 88! Discard the 88Mb limit on your Ampro LB Z80 by Terry Pinto That old saying that "Necessity Is The Mother Of Invention" certainly holds true. After purchasing my Ampro, I noticed that I was limited to a maximum of 88Mb of hard disk space. My feelings then were, WHO CARES! How could I ever fill that much space! I found a good price on a Priam V150 60Mb RLL certified hard disk and added it to the system. Well, you guessed it. It certainly didn't take long to fill up the disk. I run a BBS, Access Programming RAS, and my users were slowly eating away any free disk space I had. The time had come to enlarge the system. The problem was that I couldn't justify the expense of expanding to an 88Mb drive just to gain the additional space, and the extra 20Mb was a small addition that would disappear rapidly. The only solution was to engineer a way to utilize the fact that the Adaptec 4070 controller I used could support two hard disk drives. I purchased a copy of the source code to the Ampro BIOS and set to work writing HDS v1.00 (Hard Disk Select). Before explaining how HDS works, a brief description of Ampro's drive table is in order. This table contains the information necessary to relate the logical drives to the physical drives on the system and to select the driver routine needed for each logical drive. The table is arranged in 16 groups of 4 bytes each for logical drives A-P. The information in byte 2 is used to select the physical drive on the controller (see Tables 1 and 4). Setting bits 7, 6, and 5 to a value of 000 will select physical drive 0 on the controller while a value of 001 will select physical drive 1. Provided that both drives are physically compatible (for example, the same make and model) and are partitioned identically, simply changing bit 5 in byte 2 from 0 to 1 for a given logical drive (partition) will cause the system to access (read/write) the drive set up as SCSI drive 1 in place of the drive set up as SCSI drive 0. As you can see, the fact that both drives are partitioned the same is VERY IMPORTANT! The only thing I attempt to do with HDS is to tell the controller to use the other hard disk. HDS gives you double the disk space without the loss of any additional TPA. ---------------------------------------------------------------------- Drive A 01 00 C6 00 Floppy Drives A-D Drive B 01 11 C6 00 Drive C 01 22 86 00 Drive D 01 33 86 00 Drive E 02 44 00 FF Foreign Format Drive E Drive F 03 50 0A 01 Hard Disk Drives F-P Drive G 03 60 0A 01 Drive H 03 70 0A 01 Drive I 03 80 0A 01 | | | | | | | +--- SCSI Address | | +------ Drive Type Identifier | +--------- Physical Offset and Drive Unit Number +------------ Disk Drive ID 0 = Not Installed Table 1. Physical Driver Table ---------------------------------------------------------------------- 00 = Reserved for errors 01 = Floppy Drive 02 = Foreign Format Drive 03 = Hard Disk Drive 04 = Currently Undefined 05 = Currently Undefined 06 = Currently Undefined 07 = RAM Disk (N/Systems) Table 2. Values of the Disk Driver ID (byte 0) ---------------------------------------------------------------------- Bits 7654 Offset to base 0-F Bits 3210 Physical device address to be passed to the respective driver. (For floppies, this is the drive unit#. For hard disks, these are reserved.) Table 3. Physical offset from start of disk parameter headers and the drive unit number (byte 1). ---------------------------------------------------------------------- Floppy Usage: Bit: 76543210 Density X 0=Single 1=Double Sides X 0=Single 1=Double Sector#'s X 0=Same 1=Contiguous Track Cnt X 0=Down 1=Down Front - Up Back Alloc Unit XX 00=1k 01=2k 10=4k 11=8k Sector Size XX 00=128 01=256 10=512 11=1024 Hard Disk Usage: Bit: 76543210 LUN XXX Logical unit number (0-7) Reserved X Alloc Unit XX 00=1k 01=2k 10=4k 11=8k Sector Size XX 00=128 01=256 10=512 11=1024 Table 4. Drive Type Identifier (byte 2). ---------------------------------------------------------------------- Bit: 76543210 SCSI address 0 X This is the actual bit pattern SCSI address 1 X supplied during the SCSI select SCSI address 2 X routine. No internal address SCSI address 3 X translation or bit scaling is done. SCSI address 4 X SCSI address 5 X SCSI address 6 X SCSI address 7 X Table 5. SCSI bus address for hard disks (byte 3). ---------------------------------------------------------------------- Hard Disk Select The Ampro BIOS can be set up to accommodate hard disk space up to 88Mb. This is due to the fact that a CP/M system can address sixteen drives, A-P, of up to a maximum of 8Mb of space each. Ampro defines drives A-D as floppy drives and drive E as the foreign format floppy. These allocations are predefined and cannot be changed, although by using the SWAP utility they can be moved around. For the purposes of this article, we will assume that the original drive mapping is intact and that you have not used SWAP to redefine the drive parameter tables. In fact, the use of SWAP is not restricted, and you may feel free to swap your drives at will either before or after running HDS. With five drives being predefined, this leaves us eleven drives of 8Mb each, which gives us 88Mb of space. This will leave a TPA of about 56k. If you have elected to size your system to allow 88Mb of space, you may use HDS to 'mount' any eleven drives available to the system. What this means is that although you may have 22 logical drives attached to the system, you may only define eleven of them as currently active. This action is referred to as 'mounting' the drive. HDS will allow you to select any eleven drives available and make them active on the system. You may select an individual logical drive, a group of logical drives, or an entire physical drive. HDS will accept options passed on the command line describing what actions you want to take. Syntax: HDS [n|d] (one option allowed - global select has priority) n=logical drive number (global select) d=list of drives to select When HDS selects a drive from the appropriate hard disk, it toggles the selection. To reset the drive, you must either reselect the drive, or do a global select to drive 0. You should either select a global option or a set of individual drives. If both options are specified, the global select will occur. Examples: HDS fghi selects drives F,G,H and I from HD 1 HDS bij (the drives do not need to be consecutive) HDS c selects drive C from HD 1 HDS 0 global select to HD 0 (reset). HDS shows map of system In the first example above, HDS will attach drives F,G,H and I from logical drive 1 to the system replacing their counterparts on drive 0. The drives do not have to be contiguous, as the second example shows. In this example, drives B, I, and J are attached, replacing their counterparts on drive 0. In the third example, just drive C is exchanged. In the fourth example, a global select is issued to select all drives on logical hard disk 0. This can be used as a quick method of reseting the system. The last example, HDS is run without a command line argument. This causes the system to display a map of the available drives on the system and how they are selected. HDS will monitor both the QUIET flag and the WHEEL byte in order to control the display features and to provide system security. The use of the global select function requires that the wheel byte be set, if selected during assembly. If the wheel byte is not set, the user is given an illegal function error and control is returned to the operating system. To give you a higher level of security, I have provided a bitmap of the drives on the system. Setting any of the drives in this bitmap will secure the drive and will require that the wheel byte be set to mount that drive. ABCDEFGH IJKLMNOP Example: DRVMAP: DB 01000000 00000000b In the example above, drive B has been set as secure. This means that if the wheel byte is not set, the user could not issue a command of 'HDS B'. Attempting it would generate the illegal function error and return the user to the operating system. For use on a remote access system, I've tied the display functions of HDS to the QUIET flag. When the quiet flag is on, no screen output is generated during the selection of drives. This will enable you to include HDS in an alias and have it totally transparent to the user. With the QUIET flag off, a signon message will appear each time you run HDS. The same is true for the display function of HDS. If you call HDS without a command line option, it will give you a map of what drives are selected and from which physical drive. Table 6 shows an example of a typical run of HDS. ---------------------------------------------------------------------- A0:BASE>HDS Hard Disk Select v1.03 (c) 05/17/89 Written by Terry Pinto ZCPR v33 ZRDOS v19 Ampro BIOS v38 PHYTAB D072H (Type 3 - Loaded at 8000H) Selected Drives A - Floppy Drive B - Floppy Drive C - Floppy Drive (not installed) D - Floppy Drive (not installed) E - Foreign Format Drive F - Drive 0 G - Drive 0 H - Drive 0 I - Drive 0 J - Drive 0 K - Drive 0 L - Drive 0 M - Drive 0 N - RAM Disk O - Does Not Exist P - Does Not Exist Table 6. Example of screen display after running HDS. ---------------------------------------------------------------------- You can see from the output that HDS reads the parameter table to determine if a drive is on the system and, if so, what kind of drive it is. Notice that all four floppy drives are always defined by Ampro but that on this system drives C and D are 'not installed'. The foreign format floppy is drive E and is used for the reading/writing of disks formatted for other systems. The display shows that hard disk drives F-M are defined and are currently the drives residing on the hard disk defined on your system as being physical drive 0. Drive N is defined as a RAM Disk (N/Systems) and drives O and P do not exist on the system. If you select drives FGH and I, you get the output shown in Table 7. Notice that the drive identifier for drives F,G,H and I now show that these drives are currently attached from the hard disk defined on your system as physical drive 1. ---------------------------------------------------------------------- A0:BASE>HDS FGHI Hard Disk Select v1.03 (c) 05/17/89 Written by Terry Pinto ZCPR v33 ZRDOS v19 Ampro BIOS v38 PHYTAB D072H (Type 3 - Loaded at 8000H) Selected Drives A - Floppy Drive B - Floppy Drive C - Floppy Drive (not installed) D - Floppy Drive (not installed) E - Foreign Format Drive F - Drive 1 G - Drive 1 H - Drive 1 I - Drive 1 J - Drive 0 K - Drive 0 L - Drive 0 M - Drive 0 N - RAM Disk O - Does Not Exist P - Does Not Exist Table 7. Example of screen display after running HDS a second time. ---------------------------------------------------------------------- After the selection of the requested drives, it is necessary for HDS to perform a disk reset to log in the newly defined drives. To accomplish this, HDS must know what type of DOS you are using. A check is done to determine if you are running vanilla CP/M 2.2, ZRDOS, or ZSDOS. In either case, an appropriate disk reset is called upon to log in the new drives. During the check process, HDS also determines if you are running a vanilla CP/M or a ZCPR3 system and gets the version number. This is necessary to enable HDS to find the physical tables in your BIOS. The type of system you are running will be displayed during the signon if the QUIET flag is off. For now, HDS only detects Z33, Z34, and CP/M operating systems. Future versions may include detection of CP/M plus. Online examples from Access Programming... To enable an easier way for the remote user to use HDS, I've placed the following alias' in my ALIAS.CMD file. (The case switching symbols have been eliminated to make the alias a little easier to read). HDSEL echo;The Following Hard Disk Selections are Available;echo;echo AMPRO;echo;MSDOS;echo;ZCPR;echo;SYSTEM;if wh;echo;EXTEND;fi;echo AMPRO echo;Loading AMPRO Drivers - Please Wait...;hds 0;hds c MSDOS echo;Loading MSDOS Drivers - Please Wait...;hds 0;hds dfghi ZCPR echo;Loading ZCPR Drivers - Please Wait...;hds 0 SYSTEM echo;Loading SYSTEM Drivers - Please Wait...;hds 0 EXTEND echo;Loading EXTENDED Drivers - Please Wait...;hds 1 The HDSEL command will display the following selections: A0:RCPM>HDSEL The Following Hard Disk Selections are Available AMPRO MSDOS ZCPR SYSTEM EXTEND A0:RCPM> This give my users an online guide to what is available. Running AMPRO will attatch drive C from HD 1. This is where all the Ampro specific file are located on my system. MSDOS will load drives D, F, G, H and I from HD 1 and allow the users to access the MSDOS programs stored there. ZCPR and SYSTEM actually perform the same function for now. ZCPR will grant access to the ZCPR specific files on HD 0. The SYSTEM command will serve as a system reset. I've made BYE an alias on my system allowing me to include the command 'HDS 0' in the signoff module. This effectively resets my system for the next caller. This allows me to maintain a default status so that each new caller will enter the operating system with the same drives attatched. The EXTEND command selects all drives from HD 1 to the system. Much of my commercial software is kept here so I've set HDS to require that the wheel byte be set to do a global select to drive 1. I've also set up drive B as a secure drive. This is done by setting the corresponding bit in the drive bitmap to 1. If HDS detects the security bit on any drive passed on the command line, access will be denied. ACKNOWLEDGEMENTS Many hours of research have gone into the development of HDS. Release of this software would not have been possible without the information that was obtained from the source code of version 3.8 of the Ampro BIOS. Much of the information describing the bit selections necessary for HDS were quoted directly from the source code listing. If you would like a copy of HDS or have any questions about the software or its operation, please contact: Terry Pinto Access Programming RAS 14385 SW Walker Rd. B3 Beaverton, OR 97006 (503) 646-4937 6:00pm-10:00pm PST (503) 644-0900 300/1200/2400 8N1 PCP ORPOR StarLink 9164/222 (local exchange)