Re: 32MB is size???

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

"Paul Schlyter" <pausch@saaf.se> wrote in message 
news:e0pfuc$2s0u$1@merope.saaf.se...
> In article <vTVXf.7800$4L1.2405@newssvr11.news.prodigy.com>,
> Bryan Parkoff <none@nospam.net> wrote:
>> "Paul Schlyter" <pausch@saaf.se> wrote in message
>> news:e0oh20$2h45$1@merope.saaf.se...
>>> In article <iAHXf.51135$2O6.5759@newssvr12.news.prodigy.com>,
>>> Bryan Parkoff <none@nospam.net> wrote:
>>>
>>>> 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.
>>>
>>> No, that's not the reason ProDos reads so much faster than DOS 3.3.
>>>
>>> One can fairly easily patch DOS 3.3 so it reads about as fast as
>>> ProDos does.  A number of special DOS'es, with these patches, are
>>> known by names like Diversi-Dos, Pronto-Dos, etc --- all of them use
>>> 256-byte sectors, both at the sector level as well as at the OS level.
>>>
>>> -- 
>>> ----------------------------------------------------------------
>>> Paul Schlyter,  Grev Turegatan 40,  SE-114 38 Stockholm,  SWEDEN
>>> e-mail:  pausch at stockholm dot bostream dot se
>>> WWW:     http://stjarnhimlen.se/
>>
>> Paul,
>>
>> Well, unpatched DOS 3.3 executes 6502 instructions by using extra cycles
>> because of crossing page boundary.  ProDOS borrowed patched DOS 3.3 to
>> reduce cycles by increasing performance so crossing page boundary is
>> avoided.
>>
>> Bryan Parkoff
>
> I never denied that.  But you claimed that this page boundary stuff was
> the reason unpatched DOS 3.3 reads disk so much slower than ProDos.  And
> that's what I objected to.
>
> The reason unpatched DOS 3.3 is so slow is that it pipes all its disk
> I/O stuff through a "read one byte" (and, if writing, "write one byte")
> subroutine.  And that subroutine saves and restores an environment 45 
> bytes
> large each time it is called.  This means that if you read (or write) a 
> large
> number of bytes, those 45 bytes are needlessly swapped back and forth for
> each and every byte read.  This slows down unpatched DOS 3.3 enough to
> make it miss the next sector when it passes under the disk r/w head, 
> forcing
> DOS 3.3 to wait another disk revolution for the next sector.
>
> Compared to this "swap 45 bytes back and forth for each and every byte 
> read",
> the delay due to the page boundary stuff you mention is quite 
> insignificant.
>
> -- 
> ----------------------------------------------------------------
> Paul Schlyter,  Grev Turegatan 40,  SE-114 38 Stockholm,  SWEDEN
> e-mail:  pausch at stockholm dot bostream dot se
> WWW:     http://stjarnhimlen.se/
Paul,

    Well, I can't remember the article when patched DOS 3.3 and ProDOS had 
some ways to reduce approximately 10,000 cycles which it runs faster.

Bryan Parkoff