Re: 32MB is size???

["Bryan Parkoff" <none@nospam.net>]

"Jack Tseng" <tseng4@hotmail.com> wrote in message 
news:ryCXf.7475$t22.368@dukeread08...
> Linards,
>
> For example, 256 bytes times 65536 equals to 16,777,216 bytes total ~ 
> 16MB.
> Another example of Microsoft FAT16, 32,000 Cluster Size times 65536 equals 
> to ~ 2GB.
>
> Is it 256 bytes times "double 65536" equals to 32MB ? or 512 bytes times 
> 65536 equals to 32MB or ??? bytes times ????? equals to 32MB.
>
> Is it clear?
> Thanks!
> Jack
>
>
> "Linards Ticmanis" <ticmanis@gmx.de> wrote in message 
> news:442ee9d3$0$7753$9b4e6d93@newsread4.arcor-online.net...
>> Jack Tseng wrote:
>>> Apple DOS provides the 16 sector low-level format of DOS 3.3 for 5.25 
>>> inch disks. DOS 3.3 can store up to 16MB in size.
>>
>> As far as I know, that is not the case. Unpatched DOS 3.3 can store only 
>> 140K since it supports only 5.25 inch disks. Patched DOS 3.3 (with 
>> another hardware driver I mean) can store up to 400KB if the medium is 
>> big enough, but not 16MB.
>>
>>> New ProDOS introduced a new high level format that stores up to 32MB in 
>>> size.
>>
>> Yes.
>>
>>> Does it mean 512 bytes per sector or double "65535" ? If not that, how 
>>> does it make 32MB in size?
>>
>> The "16 sector" low level format has nothing to do with any 16MB DOS 
>> maximum; such a 16MB DOS maximum does not exist at all.
>>
>> ProDOS uses the same 16-sector low level format as DOS, *if and only if* 
>> you use ProDOS on a 5.25 inch disk. On other disks (hard disks, 3.5 inch 
>> floppies, CD-ROMs, etc.) it does not use that format.
>>
>> I don't really understand that question, though. Could you reword it?
>>
>> -- 
>> Linards Ticmanis
>
>
Jack,

    Hi, I suggest you to read "Beneath to ProDOS" and "Beneath to DOS 3.3" 
manual.  DOS 3.3 is designed to read 256 bytes per sector at this time. 
ProDOS is designed to read 512 bytes per two sectors at this time.  It shows 
that ProDOS is faster than DOS 3.3 for reading and writing because double 
sectors are stored in the RAM.  It reduces 6502 instruction cycles by 
increasing the performance.
    One block equals to two sectors or 512 bytes.  ProDOS can handle up to 
65,536 blocks to hold 32MB.  It can't increase beyond 65,536 blocks to reach 
2GB because 6502 CPU can only handle 16 bits while it loads 8 bits in both 
low and high byte to manipulate blocks.  If you want to hack ProDOS to 
support 2GB, you will need to rewrite ProDOS' source code to support 24 bits 
which it whould be 8GB (16,777,216 blocks * 512 bytes = 8GB.  It would be 
non-ProDOS.
    I have 2GB hard drive using Turbo IDE controller card for Apple IIgs. 
It allows to use 64 partitions of ProDOS 32MB which it equals to 2GB, but 16 
partitions are visible to Apple IIgs.
    Please find any technical reference of FAT16 and FAT32.  It would 
explain how 16 bits and 32 bits are used.

Bryan Parkoff


Bryan Parkoff