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View Full Version : Re: SDRAM versus DDR


Rob Stow
April 7th 04, 07:04 PM
Dave wrote:

> I have got 768 MB of SDRAM (133 MHz) on my system.
>
> If I go to a DDR mobo then how much 3200 DDR-400 would I need to
> get to roughly match the performance of the SDRAM?

Depends on whether the things you do are most
dependent on the RAM speed or the RAM quantity.

If you do things like video editting, the more RAM the better,
even if you have to settle for something a little slower than
PC3200.

If you do mostly gaming (plus trivial stuff like word processing
and web browsing) then 512 MB of low latency PC3200 should do
you very nicely.

Arnie Berger
April 7th 04, 11:59 PM
Rob Stow > wrote in message >...
> Dave wrote:
>
> > I have got 768 MB of SDRAM (133 MHz) on my system.
> >
> > If I go to a DDR mobo then how much 3200 DDR-400 would I need to
> > get to roughly match the performance of the SDRAM?
>
> Depends on whether the things you do are most
> dependent on the RAM speed or the RAM quantity.
>
> If you do things like video editting, the more RAM the better,
> even if you have to settle for something a little slower than
> PC3200.
>
> If you do mostly gaming (plus trivial stuff like word processing
> and web browsing) then 512 MB of low latency PC3200 should do
> you very nicely.

As a general rule, the greater the memory bandwidth, the faster your
code will run. However, it isn't that simple. A lot will depend upon
how well your program utilizes the on-chip caches. Typically, cache
hit ratios are around 90% or better. This means that 9 times out of
10, the data or instruction that you need will be in cache. This is
independent of SDRAM or DDR memory.

Now, if you get a cache miss and have to go to memory, then you will
see the speed of memory. Or, if you are doing a lot of disk intensive
activity, the memory speed could come into play. In any case, it isn't
a 1:1 relationship between memory bandwidth and code execution speed.

arnie

Barry Watzman
April 8th 04, 02:11 AM
Video editing is not particularly memory intensive, it's much more CPU
intensive.


Rob Stow wrote:

> Dave wrote:
>
>> I have got 768 MB of SDRAM (133 MHz) on my system.
>>
>> If I go to a DDR mobo then how much 3200 DDR-400 would I need to get
>> to roughly match the performance of the SDRAM?
>
>
> Depends on whether the things you do are most
> dependent on the RAM speed or the RAM quantity.
>
> If you do things like video editting, the more RAM the better,
> even if you have to settle for something a little slower than
> PC3200.
>
> If you do mostly gaming (plus trivial stuff like word processing
> and web browsing) then 512 MB of low latency PC3200 should do
> you very nicely.
>

Rob Stow
April 8th 04, 03:08 AM
Barry Watzman wrote:
> Video editing is not particularly memory intensive, it's much more CPU
> intensive.

Video editting when you don't have enough RAM to hold
all or at least a large portion of the clip in RAM is a
painful process. A clip doesn't have to be very big
before even 4 GB of RAM is not enough, especially since
you don't work with compressed streams like AVI or MPEG
files - you do your editting and then compress/encode the
final product.

Video encoding/compression, by contrast, needs relatively
little RAM and is more dependent on raw cpu MHz.




>
>
> Rob Stow wrote:
>
>> Dave wrote:
>>
>>> I have got 768 MB of SDRAM (133 MHz) on my system.
>>>
>>> If I go to a DDR mobo then how much 3200 DDR-400 would I need to get
>>> to roughly match the performance of the SDRAM?
>>
>>
>>
>> Depends on whether the things you do are most
>> dependent on the RAM speed or the RAM quantity.
>>
>> If you do things like video editting, the more RAM the better,
>> even if you have to settle for something a little slower than
>> PC3200.
>>
>> If you do mostly gaming (plus trivial stuff like word processing
>> and web browsing) then 512 MB of low latency PC3200 should do
>> you very nicely.
>>
>