Date   : Fri, 26 Aug 2011 16:24:23
From   : rs423@... (Mick)
Subject: [BeebSoc] Re: Amstrad emailer / DataCentre

J.G.Harston wrote:
> 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. 
>   
Forward thinking.



> The HADFS Support ROM has various of these external drive support
> functions.
>   
I'm pretty sure I only got the HADFS ROM. I can't find that now though.



>   
>> Now you've got me confused. According to my free space map for drives 0
>>     
> [...]
>
> Errr... You've lost me there... ;)
>   
I have that affect on people.  :-)


> 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
>   
Slap my face with a wet fish! Yes. I've reserved 4 HADFS drives 
67,125,248 bytes used. Perfect with a single 16k file saved on the 
drive. I must have been very tired not to notice that before.



> The ADFS free space map has a 16M "hole" at the beginning of it
> that the HADFS partition live in.
>   
Or a 64M hole for the four 16M HADFS drives.



>   
>>> 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?
>   
Are you seriously asking me? Oh, it's rhetorical ... I see. ;-)



> &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
>
>   
When you said HADFS claimed one page, you meant one private page, 
therefore one above DFS and ADFS. There is where I got confused as I 
didn't take the 'private' bit on board. HADFS actually takes ten pages 
if used solo looking at your list. It's a real shame that there isn't a 
way of using a carrier board to enable a ROM to use its own sideways 
RAM, rather than poaching I/O memory. HADFS is efficient enough though.


Thanks,


Mick.