Sinclair QL-SD, User Manual

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QL-SD User Manual 17
the correct disk!)
7.1. Preparing the QL File System Image
The step above has prepared the SD card for use with a PC - You want it to be usable with the QL,
however. So the next step is to create the DOS-File that will actually hold the QL file system. As
mentioned above, QL-SD comes with a number of pre-created file system images of various sizes -
If you can’t find one that suits your specific needs, you can create your own images: A QL image
file can easily be created on a PC using the tool
MakeImage.exe tool that should have come with
your QL-SD or downloaded from a QL software repository on the internet.
IMPORTANT NOTE:
To keep the driver lean (to fit into the available ROM space) and fast, there is no full
implementation of a VFAT32 file system in there. For this reason, the driver will only work if
the QL_BDI.BIN image file is located in
contiguous sectors on the VFAT32 SD card
partition.
This is most easily achieved by copying the image on a freshly formatted SD card, or at least
on a card that has not had files deleted from it since the last format. Deletion of files will
create small areas of free space that a ‘normal’ VFAT32 driver would collate into larger
space, re-use and allocate to files - That files are called ‘fragmented’ afterwards, because
the sectors belonging to them are not in contiguous space, but instead inter-mixed with other
files’ sectors.
The QL-SD driver is not able to handle fragmented image files. It is not even detecting
this situation, but will instead happily overwrite areas of the SD card that do not belong to the
image file - And thus might destroy other (PC-related) data on the card.
There are even tools in the PC world to de-fragment a disk (i.e. collate all files into
contiguous space on the disk) - While those tools are available and some of them would
even do the job - It is probably not worth the effort - As a general rule: If you want to put a
QL_BDI.BIN image on an SD card, simply format it first.
Start the tool, press the “New Image” Icon and select a location for the image. You then need to
decide on File system size and Group size (explained below). Press “OK” and you are done. This
new image should be stored on your freshly FAT32 formatted SDHC card under the filename
QL_BDI.BIN
. („BDI“ stands for the term „Block Device Image“ and is also used in the context of a
more general interface for QL file system access from within an emulator.)
The image file must reside in the SD-Card’s root directory. It must not be resized, renamed or
otherwise tampered with other than from the QL or a QL Emulator equipped with a proper BDI
driver. The FAT32 system may contain further files, but caution must be taken so the native QL file
system image is not harmed.
MakeImage.exe needs 4 parameters in order to create the QL disk image for you:
1. Image Filename : This is the DOS-Name of the image created - It will be shown when you
display a directory of the SD Card from the PC. The name should have the drive and root
directory designation in front of it - Make sure you choose the correct drive (the SD Card) when
you use MakeImage.exe. For the name itself, there is not much of a choice: Current versions of
the QL-SD driver will only pick up image files named “
QL_BDI.BIN ”.
2. QL Medium Name : Choose the name of the medium that you want the QL to display when
you request a directory listing - Otherwise the name is of no further relevance.