Way back in the February 1986 issue of Electron User, I reviewed Advanced Computer Products' 1770 DFS. This is a ROM which provides AP3 owners with a DFS compatible with that used in the BBC Micro. Both the BBC B+ and Master use 1770 DFS's and these are also designed to be compatible with the old 8271 DFS in the original BBC Model B.

With ACP's 1770 DFS, Electron users have the ability to access BBC B, B+ and Master discs, which greatly increases the amount of software available to them. In fact the only stumbling block is that the AP3 uses 3.5" discs whereas 5.25" is the standard on the BBC Micro. Still, you can always add a 5.25" second drive.

Now the same DFS is available on disc for Electron owners with ACP's Sideways RAM Cartridge. Simply insert the cartridge in one of the Plus 1's sockets, boot up the disc and you've got a 1770 DFS.

If you want to know what ACP's DFS is like take a look at the February issue - the disc version is identical except it runs in sideways RAM and not ROM.

So what are the advantages of having the ROM on disc? After all, it ties up the Sideways RAM preventing it from being used for anything else.

The advantage of the disc DFS is that it disables the ADFS and resets PAGE to &E00. This is the same as on an unexpanded Electron.

Compare this to &1D00 with just ADFS, &1900 with DFS and &1F00 with both ADFS and DFS. With ADFS you lose nearly 4k of memory whereas with ACP's E00 DFS you don't lose any. It avoids memory problems with long programs and the hassle of downloading software.

Programs which need PAGE to be at &E00 can still access the disc as normal. Downloaded software cannot do this and must select the tape filing system. After *FX200,2 and CTRL-BREAK the ADFS is restored, PAGE reset to what it was originally and you've got both ADFS and DFS.

ADFS can be selected with *ADFS and DFS with *DISC. This enables you to transfer your files to DFS discs. Simply *ADFS, load the file, DFS and save it.

I thought the 1770 DFS was superb but the E00 DFS is even better! I can recommend it to all AP3 owners.

Roland Waddilove