Message-ID: <67BAFB085CD7D21190B80090273F74A45B7D0B@emwatent02.meters.com.au> From: "Da Silva, Joe" To: "'opendos AT delorie DOT com'" Subject: RE: 1024 cylinder limit; anti-bloat (was DRDOS FDISK) Date: Mon, 30 Oct 2000 17:40:47 +1100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2448.0) Content-Type: text/plain Reply-To: opendos AT delorie DOT com See below ... Joe. > -----Original Message----- > From: Patrick Moran [SMTP:pmoran22 AT yahoo DOT com] > Sent: Friday, 27 October 2000 7:01 > To: opendos AT delorie DOT com > Subject: Re: DRDOS FDISK > ---- snip ---- > other OSes can use logical drives in an extended partition. However, > people > having older mother boards with older BIOS have a limit of 1024 cylinders > in > which you may boot from. So often times people will make small primary > partitions so that the boot files needed to boot the OS will be within the > first 1024 cylinders of a drive. For example. a lot of people make a small > primary partition for the Linux /boot directory of about 8MB and install > LILO in that boot record and make sure thst the entire partition is within > the first 1024 cylinders. The OS/2 boot manager or any other boot manager > must be within the first 1024 cylinders. In later BIOS, you do not need to > worry about this. many people are still using 286/386/486 machines and > most > of these BIOS have this limitation. Many of the Pentium I and II system > may > also have this limitation. It would cost more to update these BIOS than it > would cost to get a good late model new or used motherboard. > > I don't know what the limitation is on my BIOS, but all my drives are less > than 1024 cyl or they lie to the BIOS and show less than 1024. Some people > even run much older systems such as 8088/80286 and would rather run DOS > 3.3 > on them. MSDOS 3.3 has a maximum size of 32MB per primary or logical > drive. > Nobody I know uses MSDOS 4.0.) The reason they do this is because the > system > files and many of the DOS files are much smaller and take less disk space. > ---- snip ---- [da Silva, Joe] Actually, it's not the drive that lies to the BIOS (well, it does that too, but that's a different story), it's the BIOS that lies to the O/S. For recent BIOSes, when you select either Extended (IIRC) CHS, or LBA settings, what you are saying is for the BIOS to translate O/S (Int 13) CHS parameters to/from either the Extended CHS or LBA parameters of the drive. For older BIOSes, you need to load a sort of patch to the BIOS, in the MBR, using Disk Manager or equivalent. This allows the O/S to break the 504M limit (to 8G), while still operating within the Int 13 limit of 1024 cylinders. I don't know for sure, but I think the current versions of Disk Manager also add Extended-Int13 services to the BIOS to break the 8G limit (for suitable O/S only, eg. M$DOS 7.10). As for using M$DOS 3.3 to avoid bloat, I would recommend instead, DR-DOS 6. This gives you partitions of up to 2G (instead of just 32M), has reasonable memory support (note - it's EMM386 has very *good* compatibility with app's :-), yet has nice, compact executables.