Disc Transfer



DFS Explorer now has the facilities for sending or receiving disc images to your BBC computer.

This feature requires a serial cable to connect your PC to your BBC computer. Instructions for making up a serial cable can be found here.

The disc transfer features are based on the XFER 5.1 program but only has the facilities (at the moment) for sending or receiving complete disc images and not individual files.

However, a big advantage over XFER is that RLE compression is now used when transferring the data.

RLE compression works by counting the number of consecutive characters of the same value and sending a special count/byte sequence rather than the individual bytes.

You will see major benefits from RLE compression if your disc only contains a few files or lots of blank sectors.

If you have a disc full of random machine code files then you won't see much increase in transfer speeds.

I did try LZH compression but it took longer to compress the data than to actually send it so this was no use.

To use the disc transfer features, you need to make up a serial cable and connect it between your PC and BBC computer.

In DFS Explorer, there is a new menu called DFS Xfer with several options.

You need to first of all tell DFS Explorer which com port you are using so select it off the Serial Port menu.

Secondly, you need to transfer a small BBC Basic over to your BBC which acts as a server program for sending/receiving the disc images.

Select Send Basic Program off the menu and follow the instructions given on the dialog box.

If you get problems at this point and cannot get the program across, check out your serial cable connections.

Once you have the program on your BBC, save it away to disc somewhere, then fire it up !

The DFS Xfer menu contain two sub-menus for sending or receiving disc images.

Pick the BBC drive you want to use and the format of the disc in the drive, either single sided (ssd) or double sided (dsd).

After picking the DFS disc type, you will be asked for a PC filename containing the disc image to send or asking for the name to call the received disc image.

Once this is all entered, the disc transfer will commence. A progress bar will be shown on screen so you can see how the transfer is proceeding.

Once the disc is transferred, you can then load it into DFS Explorer to view the contents or run the software on your BBC as appropriate.

If things don't go to plan, a further option on the DFS Xfer menu called Trace will allow you to open a window to monitor the transfer process. You can also capture this information to disc so if you get problems, you can send me the trace file so I can help you work out where any problems may lie.

This is the first implementation of disc image transfer in DFS Explorer but it appears to work OK on my setup here.

Please ensure you have backup copies of your DFS discs before attempting to transfer them (just in case !)

Future versions may well incorporate some bufffer techniques at the BBC end to speed things up even further. Some time is being lost at the moment whilst the disc continually spins up to speed before reading/writing tracks. I should be able to improve on this by using sideways RAM or main memory to read multiple tracks at once which will improve on this issue.

As usual, if you get any problems or have suggestions to improve on this new feature, please let me know personally.

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Copyright 2006 Jon Welch
Last modified: 17-08-2010