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Partitioning and Formatting

This section describes more advanced use of the !PPortForm program, including partitioning drives.

Important. Before you attempt to format or re-format a disc please read the section Problems with older machines at the end of this manual.

What are Drive Partitions?

The ParPortFS system supports hard drive partitions. This is nothing to do with 'PC partitions' used by PC cards or emulators and alternative operating systems like ARM LINUX and RISC BSD but a way of dividing up a large 'physical' drive into several partitions or 'logical' drives. There are three reasons why you may want to do this.

  1. With operating systems before RISC OS 3.6 the maximum drive size permitted is 512 Mb. Chopping up bigger drives into a series of partitions enables large drives to be used on earlier OS's.
  2. Each partition can be protected by a password. This is useful if more than one person uses the computer or you have confidential data on your disc.

First you must understand the terms physical drive and logical drive.

A physical drive is an actual hard disc. A logical drive is a drive as it appears to the operating system and to the user. In the RISC OS desktop it's a drive icon on the icon bar. ParPortFS supports up to eight logical drives so you could have up to eight ParPortFS drive icons. This is far more than would normally be required but it does allow very large drives to be used with pre RISC OS 3.6 machines.

Partitions and removable drives

Because of the problems that partitioned removable discs can cause you are strongly advised NOT to partition removable discs under normal circumstances. A lot of confusion could be caused if you replace a disc with two (or three or four) partitions with a 'normal' disc with a single partition!

The obvious exception to this is if you want to use the system with a machine which has an OS before RISC-OS 3.6. With these machines the largest drive that can be used is 512Mb. You must therefore either format the disc to 512Mb or less (in fact, this means create a single partition of 512Mb) or split it into two partitions.

If you use just one partition then the disc will be readable (in theory) in a drive used under any other Acorn system, eg. a Cumana parallel port drive, or an IDE drive connected to any Acorn IDE interface. If you use more than one partition then only the FIRST partition will be visible to other filing systems. All partitions will be usable if you use the disc in an IDE drive connected to an APDL ideA interface, but to ensure they all appear it will probably be necessary to reset the computer after inserting the disc or to put the disc in the drive before switching on the machine.

Using the PPortForm program

Although it is called a formatting program modern drives are actually formatted by the manufacturers and all that is necessary is to write the Boot Block, Map, Root Directory structure and other essential data to the drive. This is called 'initialising' and takes only a couple of seconds.

When you run the program it will display the characteristics of the selected drive. You will then see a menu with the following options -

  1. Add new partition to table
  2. Delete partition from table
  3. Edit drive parameters
  4. Change drive interleave
  5. Clear bad blocks
  6. Initialise all drive partitions
  7. Initialise ONE drive partition
  8. End

Instead of describing these individually I will go through the process of initialising a new, unformatted, 1 GB disc drive with two partitions, one of 320Mb and one using up the rest of the available space.

First select Option 1. The program will inform you how much space you have available to allocate, and with a 1 GB drive this might be something like 988 Mb (drives sizes are nominal). Enter the size of the first partition, 320, and press RETURN. You will be told that you have 668 Mb available (988 minus 320). Enter 688 and press RETURN again. The program will now tell you that you have 0 mb left (it's all been used up) so just press RETURN and the menu will come back again.

Now select 6 to initialise the drive partitions. You will be asked if you want the drive to be 'bootable'. It is unlikely you would want to 'boot' from a parallel port drive, if you really want to do so it is possible, but you would normally enter 'N'.

You will next be asked if you want a RISC OS 4 style format with long filenames. If you are using the drive on any OS version less than 4.02 you should enter 'N', otherwise enter 'Y'.

You will see various messages as the partitions are initialised and then, when the menu re-appears, select 9 to finish.

In this example, as you have partitioned the drive it is best to quit the parallel port software and re-run it so that it can re-initialise itself with the correct drive icons.

As you can gather, if you had wanted to have just a single logical drive you would have entered the full drive size for the first partition.

Warning If your computer is fitted with an OS less than 3.6 do not attempt to create a partition greater than 511Mb. PPortForm may appear to create and initialise the partition but it is larger than the maximum permitted for these machines and will cause serious problems as the drive fills up with almost certain loss of data.

Drive names

As has already been described you can set the name of each drive or partition from the drive menu. Each drive must have a unique name or the computer will be unable to distinguish between them and you will constantly get 'Ambiguous disc name' errors.

The PPortForm program assigns default drive names based on the day and time of day rather like formatting a floppy disc. The name is in the form

      <day><hour><minute>-<Partition number>

For example, a drive with three partitions formatted on Tuesday at 10.27 would have the partitions named -


This isn't particularly elegant but most users will want to rename them anyway. It does serve the main purpose which is to ensure that removable discs are given unique names.

Partitioned discs on other filing systems

The partitioning system used by ParPortFS is identical to that used by the APDL ideA IDE interface. Partitioned discs can therefore be moved between these two systems without problems. Unpartitioned discs have a 'standard' Acorn format and can therefore, in theory, be used with any other Acorn filing system. This will only be of interest if you have a SparQ internal IDE drive fitted to another computer.

If you do partition a disc then, should you move it to another filing system only the first partition will be visible. This can be used normally without problems.

Deleting a partition

This option is used to remove a partition. If a drive has been formatted and you wish to change the number or size of the partition(s) you will have to use this to remove the old partitions before you can install the new one(s). Note that altering the partition table normally means you will have to re initialise the drive and lose all the data on it.

Clear bad blocks

This will verify the drive and swap any blocks which return errors with spare blocks.

Edit drive parameters

This is used to change the drive parameters from the standard values for the drive. Unless you are sure of what you are doing you should not alter any of these.

Change drive interleave

Almost all modern drives are set to use a 1:1 interleave and this will be suitable for most computers. On older machines or with very old drives it may be possible to speed up data transfer by altering the interleave but unless performance is disappointingly slow it is unlikely that it will have any effect. With some drives this can completely wipe all data from the drive so you will need to repartition and initialise it.

Initialising a single partition

Normally you would only want to initialise partitions when you first install a drive, and you would then want to initialise them all. However, there may be times when you would want to initialise just a single partition, for example, if you no longer want any of the data on a partition then it is quicker to re-initialise it (wiping out all the files) rather than deleting them, or you may have a 'broken directory' which can be difficult to remove by other means.

When using this option be absolutely sure you are selecting the correct partition to initialise. If you choose the wrong one you will be unable to recover the data.

Partitions are identified by number, starting at 1. To equate this to the drive icon, partition number 1 would be the right hand icon, number 2 the next icon to the left, icon 3 the next, and so on.


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