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MacPro RAM - HW4 reports different amount from OSX

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JulianMoney-Kyrle

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MacPro RAM - HW4 reports different amount from OSX

PostMon Jun 13, 2011 4:02 pm

Having now received and installed my additional RAM, I now have 24GB in a 2007 quad-core MacPro that officially supports up to 16GB. OSX reports the full 24 GB, but when I start HW4 without a sample sets installed it reports only 16GB free. So far I have had no trouble with Freiberg Surround at maximum quality 24-bit, but that is supposed to take around 14GB. Still, I am wondering what is going on here, and whether I will be able to load anything larger.

Julian
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B. Milan

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Re: MacPro RAM - HW4 reports different amount from OSX

PostMon Jun 13, 2011 4:11 pm

Hello Julian,

This is due to Mac OS X allowing up to 2/3 of your overall RAM to safely be used.16 GB is 2/3 of 24GB so that sounds right. If you search this forum you will find many discussions about this subject from other users in the past as well. If you try to use more than 2/3 of that memory then OS X may page the data to the hard drive which can result in audio glitches and/or MIDI glitches. Thus Hauptwerk reports the available memoy that OS X says is "safe" to use.

I hope that helps.
Brett Milan
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MILAN DIGITAL AUDIO

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JulianMoney-Kyrle

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Re: MacPro RAM - HW4 reports different amount from OSX

PostTue Jun 14, 2011 7:41 pm

Dear Brett,

Thank-you for pointing that out. I will check out the previous Forum discussions before troubling you any further, though it does make me wonder what happens with the large, wet, surround sample sets that can take up to 26GB or even more, as there can't be many computers that could manage more than 32GB. And it seems a bit odd that OSX would start to use the page file after reserving (in my case) 8GB, most of which probably wouldn't be used by anything else.

With Best Wishes,
Julian
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mdyde

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Re: MacPro RAM - HW4 reports different amount from OSX

PostWed Jun 15, 2011 6:05 am

Hello Julian,

Here are some relevant on the subject of paging and how much memory can safely be used on OS X (and Windows):

http://forum.hauptwerk.com/viewtopic.php?f=16&t=7189&p=50587#p50587
http://forum.hauptwerk.com/viewtopic.php?f=6&t=6862&p=48762#p48775
http://forum.hauptwerk.com/viewtopic.php?f=4&t=5100&p=35238#p35238

E.g.:

There are lots of previous posts covering how OS X works with regard to memory and paging. Searching for 'active' and 'page' finds quite a few, e.g. here are some of the more recent ones:

viewtopic.php?f=16&t=6419
viewtopic.php?f=4&t=5100&p=35238
viewtopic.php?f=4&t=4563&p=31355

Brief summary: OS X will allow an application to fill its memory up to about 2/3, then it will start preparing to page data out (mirroring it to disk), giving slow loading. As long as no other applications or background processes run, you won't necessarily get audio glitches beyond that point, but if they do then you probably will. So up to 2/3 is safe.

Windows works differently, and will sometimes (especially if it's a fairly clean Windows installation) allow an application to load more data into memory. As long as you don't get the Hauptwerk low-memory warning then no data should have been paged to disk. On my PC, I find that in practice (perhaps because it's no longer a clean Windows installation) that happens at around the 2/3 mark anyway.

However, if another application then runs on Windows, Windows might be more aggressive than OS X in trying to page Hauptwerk's memory out, and the resulting performance impact (e.g. audio glitches) can be worse than OS X (because OS X has already prepared itself to handle the eventuality by mirroring the data).

Hauptwerk actively tries to prevent Windows paging the data back out if you have the 'Keep sample set memory active' option ticked on the 'General settings | General options | Audio engine' screen tab (see on-screen question-mark help for that setting for more details).

Generally, on either Windows or OS X you should be fine as long as you don't ignore (or disable) Hauptwerk's low-memory warning, and (especially on Windows) as long as you don't then launch any other applications if you've nearly filled the memory.
Best regards, Martin.
Hauptwerk software designer/developer, Milan Digital Audio.

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