To: opendos AT delorie DOT com Date: Fri, 16 Feb 2001 03:26:24 -0800 Subject: Re: Max. drive letter, etc. (was Hard Disk 20gb and dos) Message-ID: <20010216.032625.-270235.0.domanspc@juno.com> X-Mailer: Juno 4.0.11 MIME-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Juno-Line-Breaks: 0-64,66-108 X-Juno-Att: 0 X-Juno-RefParts: 0 From: Robert W Moss Reply-To: opendos AT delorie DOT com From 'Upgrading and Repairing PC's', by Scott Mueller, sixth edition, 1997, QUE Books. ISBN: 0-7897-0825-6..... PAGE 762: SCSI Most systems support up to four SCSI host adapters, each with with up to 7 hard disk drives for a total of 28 physically installed drives. (Since this book was published I recall reading some place about a new super wide SCSI setup where you can install 16 devices per adapter.) (?) ROM BIOS CAPACITY LIMITATIONS In addition to the capacity limit of 504M, the standard ROM BIOS is limited to supporting only two hard disk drives. The enhanced BIOS is limited to 128 drives maximum. Most SCSI and IDE adapters get around the standard BIOS two-drive limits by incorporating an enhanced BIOS on board that takes over the disk interface. Some of the newer adapter on-board BIOS versions support booting from CD-ROM drives as well. OPERATING-SYSTEM Capacity Limitations IBM and M$ officially say that DOS 5 and later versions will support up to eight physical hard disks. IBM says that OS/2 1.30.1 and later versions (including 2.x) support up to 24 physical hard disks, and because OS/2 includes DOS, that implies that DOS under OS/2 would support 24 physical drives as well. (Since I have never installed over four disks of any kind on my computers, and since DOS, OS2, and Windoze all number the hard disks, CD's, tape drives automatically, the only time I could see you needing to identify a disk manually would be when using ASSIGN to give a disk or folder a specific ID. Then that would be Nullified next time you rebooted(?). All my networking and DOS classes seem to be rooted in this same concept, ie" last drive=Z. ) When DOS boots it automatically assigns C: to the first primary partition on the first hard disk and then assigns D:, E:, etc.. to all the primary partitions it finds and then assigns the remaining Alpha ID's to the logical partions on all extended partitions. After that it assigns all the removable drives and CD ROM drives. So what happens when it hits 24? ANYONE?? If SCSI can can have 28 drives how are they numbered? If the Enhanced BIOS allows up to 128 drives How Are They Numbered, or is that just for UNIX and LINUX, where they list all drives individually by NUMBER and type. Personally, I see no use for so many drives/devices except in a network server, and then it would have to have a pretty big , fast CPU, or 2/4/6/9 CPU's, and 500+ MGB fast memory just to keep track of it all. BOB 'DOMAN' MOSS "I know nothing, Colonel Klink" On Fri, 16 Feb 2001 18:32:29 +1100 "da Silva, Joe" writes: > Oh, yeah - that reminds me ... does anyone know for > certain that this 24 drive limit is real, or are people > simply assuming this because there are about 24 > letters (26 actually) in the English alphabet? > > I remember reading an old Micro$oft manual that > said you could have *more* drive letters than there > were letters in the alphabet, so that the drives above > "Z:" would be "[:" and so on, as per the ASCII > character set ... > > Joe. > > Speaking of other (possible) myths, I also vaguely > recall reading somewhere that the often quoted > statement, that "if you have two drives on an IDE > cable, then the slowest drive will determine the > speed (transfer rate) of both drives", is a myth ... > > > -----Original Message----- > > From: Bernie [SMTP:bernie AT mbox302 DOT swipnet DOT se] > > Sent: Friday, 16 February 2001 17:46 > > To: opendos AT delorie DOT com > > Subject: Re: Hard Disk 20gb and dos > > > > Pat wrote: > > >Yes the is very true. DOS only has the cpability of 24 total > drives, > > >whether they be physical or logical or a conbination of both. So > why use > > >an 8GB drive for FAT 16? Really seems rediculous to me. > > > > I know that, still I have more than 10GB for DOS (MS-DOS 6.2, two > drives) > > here. I have no idea what it is. My hope is that sometime this > week (ie. > > tommorow) or the next I'll get my new parts. With a new 46.1GB HD > I'll > > start over with a fresh set of GBs - not even copying the c:\dos > directory > > :) > > //Bernie ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/tagj.