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RE: W2K RAMlimits



<x-charset iso-8859-1>>is the issue that there's no way to create a RAM drive in Windows, or
Photoshop
>will detect that and flat out refuse to use it?  If the former
>(there's no RAM filesystem driver) it makes sense; it would be very
>unpleasant to do with user-mode code, and Adobe's not in the
>filesystem business.  If the latter -- i. e. it's possible to create a
>RAM-based filesystem -- and Photoshop will refuse to use it for its
>swapfile, this seems rather contrary of it.

It is primarily the latter.  Photoshop generally refuses to use RAM for
certain operations and will only use itsown virtual memory for those
operations which it gets by swaping memory to and from the designated
scratch disks.  In Windows one can crate a RAM disk and designate it as a
scratch disk which Photoshop in all probability will use as a source for its
virtual memory.  However, one runs into some practical problems such as
enough actual physical RAM to support the operating system functioning as
well as Photoshop's working operational overhead in addition to that needed
for the RAM disk which has to be from 3-5 times the size of the largest
image file that is to be worked on.  One could also face the practical
problem of sometimes needing to access both RAM and the RAM disk
simultaneously for different purposes and operations, which might result in
having to alternate between accessing the RAM  and the RAM disk which will
then slow down the system to the point that one has not gained anything by
creating and using the RAM disk as a scratch disk.

As for your other comments, I cannot address them since such issues are
beyond my understanding.

-----Original Message-----
From: owner-epson-inkjet@leben.com
[mailto:owner-epson-inkjet@leben.com]On Behalf Of Robert L Krawitz
Sent: Friday, June 14, 2002 4:46 PM
To: epson-inkjet@leben.com
Cc: epson-inkjet@leben.com
Subject: Re: W2K RAMlimits


   From: "dickbo" <dickbo@btopenworld.com>
   Date: Fri, 14 Jun 2002 21:59:04 +0100

   Photoshop will not allow it and neither I suspect will Adobe
   because there are many millions of users who do not or cannot
   install volume RAM.

Bear with me, since I'm not familiar with Windows, but is the issue
that there's no way to create a RAM drive in Windows, or Photoshop
will detect that and flat out refuse to use it?  If the former
(there's no RAM filesystem driver) it makes sense; it would be very
unpleasant to do with user-mode code, and Adobe's not in the
filesystem business.  If the latter -- i. e. it's possible to create a
RAM-based filesystem -- and Photoshop will refuse to use it for its
swapfile, this seems rather contrary of it.

   Mind you with a nifty hard drive it is hardly worth the bother
   anyway

I don't think I'd agree with that at all.  RAM has 10-100x more
bandwidth (the very fastest disks today top out at about 50 MB/sec;
RAM bandwidth varies with the memory architecture but these days it's
typically between 1 and 3 GB/sec on Intel platforms) and about
100,000x better latency (~100 ns for RAM, ~10 ms for disk).  Again,
I'm not familiar with how well Photoshop optimizes its use of the swap
file, but if it's not able to do I/O in close to megabyte chunks it's
going to be latency-bound (which means really disastrous slowdowns)
rather than bandwidth-bound (which is still bad, but not nearly as
bad).

--
Robert Krawitz <rlk@alum.mit.edu>      http://www.tiac.net/users/rlk/

Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom -- mail lpf@uunet.uu.net
Project lead for Gimp Print/stp --  http://gimp-print.sourceforge.net

"Linux doesn't dictate how I work, I dictate how Linux works."
--Eric Crampton
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