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Differnce between SDX and FDX

Posted: 19 Dec 2013 13:43
by thewiz

From a Memu emulation point of view is there a difference between handling SDX and FDX disks when using mfloppys?


Re: Differnce between SDX and FDX

Posted: 21 Dec 2013 01:03
by AndyKey
When using MFLOPPY or .mfoppy files, you don't need to worry about whether the floppies are to be used with FDX or SDX.
The disk formats themselves are independent of the hardware used to access them.

So a type 03 floppy works fine in an FDX or SDX.
Note that although on CP/M you can re-CONFIG drive types on the fly, the SDX BASIC ROM providing USER LOAD etc.. is hard coded to either type 03 or type 07, so if you want to access your floppy data from MTX BASIC, you have to get that right.

Also, types 00 .. 07 apply equally to 3.5" and 5.25" media.
eg: a type 07 5.25" floppy has the same number of sides, tracks, sectors per track and bytes per physical sectors as a type 07 3.% floppy.
You could make an image of a 5.25" floppy, and write it back to a 3.5" floppy, and it would work.

Although FDXs were the only machines with type 10 .. 13 8" floppies, these type code were understood by the SM1 computer, and the floppies were interchangeable.
And, the type 10 code has skew, so that its physical layout matches the MDS system.

As for MEMU, well, MEMU only emulates the SDX floppy disk controller (courtesy of Bill Brendlings code dontation).
MEMU doesn't emulate the FDX floppy disk controller.
But given the above, no problem, just supply an .mfloppy image to MEMU - it doesn't matter if it came from a floppy used in an FDX.

Re: Differnce between SDX and FDX

Posted: 21 Dec 2013 11:00
by thewiz
Thanks Andy.

Did the system disks that came with the SDX and FDX the same?

Re: Differnce between SDX and FDX

Posted: 21 Dec 2013 11:43
by Dave
Hi Paul,

No, in fact, I think that there were at least 5, subtly different ones ....

1. Initially, the FDX, Type 03, 54k CP/M system disk
2. Essentially the same as 1, but with single disk Copy, Format, etc.
3. A non-CP/M system disk for a single drive FDX with no 80 Column board
(2 and 3 were for what Memotech first described as an "SDX")

For what are most of often thought of as SDX systems, with the drive interface that attached to the cartridge port.
4. Type 03, 59k CP/M system disk for the first SDX style with external disk
(Probably also available in non-CP/M version)
5. Type 07, 59k CP/M system disk for the "new" style SDX with internal disk
(This controller only supported a single disk)
6. Also available in non-CP/M mode


Re: Differnce between SDX and FDX

Posted: 22 Dec 2013 23:05
by AndyKey
Dave is right that there are probably quite a few system disk images.

The 54K v 59K system difference is important.
SM1 and FDX were typically shipped with 54K system disks, and I speculate this could be to leave some high memory to be able to load a hard disk driver into.
Strangley, Icicle Works only works with a 54K system, reason unknown.
SDX typically shipped with 59K system disks.
This leaves more space for programs, so very large CP/M programs (can't think of an example) might need 59K system.
The SDX BASIC ROM needs a 59K system.

SDX system disks are likely to have handy COPY commands and alternative FORMAT programs.

System disks are not a problem on any Memotech.
We can make 54K or 59K system discs, with whatever set of files we want, relatively easily.

Things only get trickier when want 5.25" or 8" disks...

Re: Differnce between SDX and FDX

Posted: 29 Dec 2013 11:17
by thewiz
Thanks for all the info.

So is sys.mfloppy in the mfloppy package an untouched SDX type 07 System Master disks?

Is the sys54.mfloppy a home made SDX type 07 you created Andy? If so was it based on sys.mfloppy or a FDX System Master? Have I got that completely wrong and it is another untouched SDX type 07 System Master, just happens to be 54Kb?

If true, do we have an untouched SDX type 03 System Master? Dave, is that what you emailed me?

As with tapes, I am trying to collect images of commercially released disks that are Memotech specific.