My note below specifically addresses what a RAM disk might be able to do
operating as a device driver and not as an application. Device drivers
have full authority to do whatever the hardware is capable of and the OS
allows them to do. Applications do not. A RAM disk should certainly be
able to utilize PAE (Physical Address Extensions) if, like my system,
it's supported by the hardware. PAE allows support of up to 64GB.
As to what those "folks over here" tell you that Windows can do I would
advise you to ignore them and choose Microsoft as your authority on
Windows capabilities. I would suggest you start here.
<http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx>
And re-reading that myself I realized that my attempt to set "the 3GB
switch" in boot.ini was likely successful since I have XP Professional.
However, it requires that the application itself be aware of the
additional memory and figure out how to use it since normal memory
addressing will limit the app to 2GB. Whether PS recognizes the 3GB
switch I don't know.
Chuck Norcutt
khen lim wrote:
> That's where I get most confused, Chuck. I read with great delight about
> Windows' ability to access beyond the first 2GB via your Microsoft MSDN link
> but I keep getting folks over here telling me no, Windows only reads 2GB and
> nothing more. The thing is you mentioned about modifying the boot.ini file
> so that Windows can and will identify GB #3 and #4 and then assign them to
> applications. That would be good but what does one write to modify this
> file? Secondly with computers these days using unified or shared memory
> architecture (with graphics adaptor), would GB #3 and #4 be assigned instead
> to such devices to use so that the first 2GB can be left to the operating
> system. I'm confused as you can see.
>
> K.
>
>
>
> 2009/8/15 Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
>
>> If the hardware is capable of addressing more than 4GB via bank
>> switching or direct 64 bit addressing, some suitable software should be
>> able to use the upper memory without interfering with Windows claims on
>> the lower 4GB... assuming that Windows agrees to let it.
>>
>> Chuck Norcutt
>>
>> Mike Lazzari wrote:
>>>> Yes, XP only addressable to 2GB, as I memtioned below I have assigned
>> 2.5GB
>>>>> as RAMDISK with Vsuite Ramdisk, the software can access to the hidden
>>>>> memory.
>>> I've thought about setting up a RAMdisk as I had on my old 8086 but
>>> don't see much benefit. In that box I had a big RAMdisk card full of
>>> memory which originally cost over $2k. Maybe I'm wrong about the current
>>> systems and should try a RAMdisk.
>>>
>>> First of all I thought that windows32bit could address something like
>>> 3.2gb? At least that's what my computer reports depending on switches
>>> set in boot.ini. I believe it reserves some of that memory for its own
>>> use, e.g. addressing the video. Maybe that's where you get the +/-2gb
>>> _usable_ memory. In any event the memory between the usable amount and
>>> the addressable 3.2gb would not be available for a RAMdisk. Or at least
>>> it would be counter productive as it reduces the usable amount addressed
>>> directly by windows for apps. Perhaps it would be beneficial if you had
>>> more that 4gb installed on a 32bit system.
>>>
>>> Secondly, How does windows address the RAMdisk? I assumed that it would
>>> have to page it in/out in blocks using available memory? If so this
>>> would increase the memory windows reserves and further reducing direct
>>> access memory used for apps. Also this paging would be a bottleneck
>>> slowing the RAMdisk memory. True, still much faster than a swap to hard
>>> disk but wouldn't it be faster to just let windows use the memory and
>>> paging block for apps? It seems to me that with 4gb of RAM on a 32bit
>>> system a RAMdisk would have to be smaller than 1gb and that seems hardly
>>> worthwhile. But my presumptions may easily be way out of date.
>>>
>>> Mike
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