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Re: The AOD Virtual Partition Specification - First Draft - 2016-04-04 -

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"James Harris" wrote:
> Mike Gonta wrote:

>> The AOD Virtual Partition Specification
>> An alt.os.development Community Project
>> - First Draft - 2016-04-04 -
>>
>> The Virtual Partition  makes  it  possible  for  a  hobbyist
>> system to manage  a  FAT32  volume  as  easily  as  a  FAT12
>> floppy  disk  image.   Restricting  access  to   the    root
>> directory combined with the  small  sizes  of  the  FAT  and
>> root directory tables, resulted in a  simple  FAT12  driver.

> Can you quantify the difference - say in lines of code for
> the source or bytes for the object code - between a
> full-and-complete FAT32 driver and an equivalent driver
> for your proposed structure?

Hi James,

How long is a piece of string?
One is a subset of the other and thus smaller, simpler and
easier.

> If I may make some criticisms (which are intended to be
> helpful, of course) of your proposal I would say:
>
> The description needs to begin not with what a VP does but
> what it _is_.

The Virtual Partition is nothing and does nothing.
The FAT32 volume is completely FAT32 (by the MS
specification). It is only "formatted" slightly different.
There is nothing added or changed. Existing software is
totally unaware of it's purpose.

> For example, "A VP is a specific way to lay out the
> initial disk blocks of a FAT32 volume, as detailed below.

There is absolutely no lay out.

> Organising the beginning of the volume in the way
> suggested allows the software which accesses it to be
> reduced in size by x%. This, in turn, allows the driver
> software to be included in a volume boot sector which, at
> 512 bytes, is not large enough to work with a generic
> FAT32 volume."

Nothing is organized.
The Virtual Partition is simply a couple of "tricks of the
trade" that make life easier. For example, ancient DOS used
the trick of requiring the two named files to be 1st and 2nd
in the root directory so that only the first sector of the
root would have to be loaded.

> "This is often better than having the volume boot sector
> load a FAT32 driver because ...."

The web is full of examples of single sector boot loaders
for FAT32 (simply more tricks).

> Is "virtual partition" the best term? It seems more to be
> a specific type of FAT32.

It really has nothing to do with FAT32.

> Perhaps a name like "FAT32mg" would be clearer? (Lots of
> things could be called virtual partitions.)

It's a partition in the manner in which the driver
recognizes it. The only difference is the way in which the
driver locates and handles the three major components. The
data still follows the root which follows the FAT, but the
(virtual) sizes of the tables are not used to calculate the
beginning/s of the following table/s.

PS. I realize that your "examples" were my examples. But
those are not things that it "does", rather they are
analogies to the simple FAT12 driver and the Virtual
Partition enabling the same simplicity with FAT32.


Mike Gonta
look and see - many look but few see

http://mikegonta.com
http://tawk.to/mikegonta

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Thread

The AOD Virtual Partition Specification - First Draft - 2016-04-04 - "Mike Gonta" <mikegonta@gmail.com> - 2016-04-04 14:38 -0400
  Re: The AOD Virtual Partition Specification - First Draft - 2016-04-04 - James Harris <james.harris.1@gmail.com> - 2016-04-04 22:35 +0100
    Re: The AOD Virtual Partition Specification - First Draft - 2016-04-04 - "Mike Gonta" <mikegonta@gmail.com> - 2016-04-04 18:51 -0400

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