Date   : Thu, 25 Aug 2011 01:47:29
From   : jgh@... (J.G.Harston)
Subject: [BeebSoc] Re: Amstrad emailer / DataCentre

Mick wrote:
> The Olympic bug strikes <eek!>. The version of HADFS I got from you
> years ago didn't do hard discs at all which is the reason I didn't use

All versions of HADFS pass access to unsupported drives to OSWORD
90 which external software can use to provide extra drives. In the
manual there is code for a simple RAMDisk, and on the System disk
there are two simple RAMDisks. For testing manipulating very large
files (eg ensuring BPUTting past the end of the largest physicallt
possible file size didn't wrap round to EXT=0!) I wrote a RSDisk
which talked to a 16M partition on an A5000 at the other end of a
serial link.

The HADFS Support ROM has various of these external drive support
functions.

> Now you've got me confused. According to my free space map for drives 0
[...]

Errr... You've lost me there... ;)

With an HADFS and an ADFS partition coexiting on the same device,
you should have:
  ADFS drive 0:  used: 16,777,216  free: 520,091,904
  HADFS drive 4: used:      2,816  free:  16,774,400

The ADFS free space map has a 16M "hole" at the beginning of it
that the HADFS partition live in.

> > HADFS claims a single page of workspace, so with only DFS and HADFS
> > claiming memory PAGE is as &1A00. If you want to lose floppy disk
> > access you could remove DFS and PAGE will drop to &1800.
> >
> 1 page is modest compared with ADFS. Why &1800? Do you mean &0F00?
> Before I added DFS, page was at &0E00.With DFS, it rose to &1900.

Where would HADFS put the file buffers?

&0E00 : Channel 25
&0F00 : Channel 26
&1000 : Workspace
&1100 : Directory sector 1
&1200 : Directory sector 2
&1300 : Directory sector 3
&1400 : Channel 27
&1500 : Channel 28
&1600 : Channel 29
&1700 : Private workspace if no other ROMs claim workspace
&1800 : Default PAGE if no other ROMs claim workspace

If DFS is present as well, you get:

&1700 : DFS private workspace page 1
&1800 : DFS private workspace page 2
&1900 : HADFS private workspace
&1A00 : Default page if no other ROMs claime workspace

-- 
J.G.Harston - jgh@...      - mdfs.net/jgh
There are three food groups: brown, green and ice cream.