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From: Paul Keinanen on 19 Jan 2010 04:19
On Sun, 17 Jan 2010 13:09:28 -0800, D from BC
<myrealaddress(a)comic.com> wrote:

>I'm tried out a trial version of 'Ramdisk' and set aside 4G of memory
>(I have 8G) to be used as a ramdrive for the raw file created during
>an LTSPICE simulation..
>
>Conclusion
>Yup. It's faster.
>Helps with long smps simulation.

While I fully understand the benefit of using a RAM disk on a 32 bit
platform (e.g. 386+) with a large physical RAM running some 16 bit
operating system (MS-DOS/Win 3.x), I do not understand why anybody
would want to run some kind of RAM disk on a 32 bit virtual memory OS
(except CDROM/Flash booted systems).

On a virtual memory operating system, the page fault mechanism has
much less overhead than the traditional file I/O.

Exactly for this reason large (hundreds of GB) disk based data bases
are handled in 32/64 bit virtual memory operating systems as memory
mapped files, actually treating the small (1-64 GiB) RAM just as a
large L3 cache.

If some RAM disk implementation is actually going to give some
improvement, much more improvement could be gained by persuading the
software vendor to understand, how virtual memory is effectively used.

From: Michael on 19 Jan 2010 13:47
On Jan 17, 1:09 pm, D from BC <myrealaddr...(a)comic.com> wrote:
> I'm tried out a trial version of 'Ramdisk' and set aside 4G of memory
> (I have 8G) to be used as a ramdrive for the raw file created during
> an LTSPICE simulation..
>
> Conclusion
> Yup. It's faster.
> Helps with long smps simulation.


You have 8 G of RAM? What OS? What mainboard? How did you do that?

Michael
From: Spehro Pefhany on 19 Jan 2010 14:43
On Tue, 19 Jan 2010 10:47:39 -0800 (PST), Michael
<mrdarrett(a)gmail.com> wrote:

>On Jan 17, 1:09�pm, D from BC <myrealaddr...(a)comic.com> wrote:
>> I'm tried out a trial version of 'Ramdisk' and set aside 4G of memory
>> (I have 8G) to be used as a ramdrive for the raw file created during
>> an LTSPICE simulation..
>>
>> Conclusion
>> Yup. It's faster.
>> Helps with long smps simulation.
>
>
>You have 8 G of RAM? What OS? What mainboard? How did you do that?
>
>Michael

You can get 24G with Win7 64 and an I7 1366 (6 SIMM sockets for triple
channel), but the 4G DDR3 PC3 12800 sticks are still extremely
expensive (down from obscenely expensive a few months ago-- about
$1600 US retail for 24G right now (Mushkin).

From: D from BC on 19 Jan 2010 17:46
On Tue, 19 Jan 2010 11:19:09 +0200, Paul Keinanen <keinanen(a)sci.fi>
wrote:

>On Sun, 17 Jan 2010 13:09:28 -0800, D from BC
><myrealaddress(a)comic.com> wrote:
>
>>I'm tried out a trial version of 'Ramdisk' and set aside 4G of memory
>>(I have 8G) to be used as a ramdrive for the raw file created during
>>an LTSPICE simulation..
>>
>>Conclusion
>>Yup. It's faster.
>>Helps with long smps simulation.
>
>While I fully understand the benefit of using a RAM disk on a 32 bit
>platform (e.g. 386+) with a large physical RAM running some 16 bit
>operating system (MS-DOS/Win 3.x), I do not understand why anybody
>would want to run some kind of RAM disk on a 32 bit virtual memory OS
>(except CDROM/Flash booted systems).
>
>On a virtual memory operating system, the page fault mechanism has
>much less overhead than the traditional file I/O.
>
>Exactly for this reason large (hundreds of GB) disk based data bases
>are handled in 32/64 bit virtual memory operating systems as memory
>mapped files, actually treating the small (1-64 GiB) RAM just as a
>large L3 cache.
>
>If some RAM disk implementation is actually going to give some
>improvement, much more improvement could be gained by persuading the
>software vendor to understand, how virtual memory is effectively used.


afaik LTSPICE does not attempt to fill memory and then spill over to
virtual memory.
afaik LTSPICE directly dumps it's data onto disk.

I've watched the ltpsice .raw file grow in size as a simulation runs.
Ltspice doesn't first fill physical memory and then switches to
virtual memory. Seems to me Ltspice dumps straight to physical disk
disregarding whatever system memory exists..

From: D from BC on 19 Jan 2010 17:57
On Tue, 19 Jan 2010 10:47:39 -0800 (PST), Michael
<mrdarrett(a)gmail.com> wrote:

>On Jan 17, 1:09�pm, D from BC <myrealaddr...(a)comic.com> wrote:
>> I'm tried out a trial version of 'Ramdisk' and set aside 4G of memory
>> (I have 8G) to be used as a ramdrive for the raw file created during
>> an LTSPICE simulation..
>>
>> Conclusion
>> Yup. It's faster.
>> Helps with long smps simulation.
>
>
>You have 8 G of RAM? What OS? What mainboard? How did you do that?
>
>Michael

win 7
gigabyte ga-ma770t-ud3p
Supports 16G mem

Freaky huh?
I dished out a bit more coin just to test out ramdisk apps with
ltspice.

Whenever I click on a new test point, the graphing seems faster as
ltspice is accessing the .raw file from memory and not from a spinning
drive.

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