Synchronous vs asynchronous

[leandrodafontoura]

Can someone please explain to me the diference? Wich one should I get, synchronous memory, or highest possible? What are benchmarks in file transfer, gaming loading and fps?

 

[blazorthon]

All system RAM is synchronous. the s in ddr Sdram, ddr2 Sdram, and ddr3 Sdram stands for synchronous.

Wikipedia can probably go into further detail about the differences between the two than I can but rest assured all RAM being manufactured today is synchronous.

Its been a while since we used asynchronous RAM as system memory in mainstream computers.

 

[MrBig55]

Nowadays this term is used for cpu/memory overclocking. If the memory runs at the speed of the Front side bus, then it is synchronous, else it is not. Ex.:

a core2duo with a 1066Mhz FSB means 4x266Mhz. Synchronous ram should be 533Mhz, or 2x266Mhz. In this forum this is called a 1:1 ratio.

Say you change the ram multiplier, then it will be asynchronous as the speed will differ from the FSB speeds.

There is performance hit when ram is asynchronous from the FSB (using any other than x2 multiplier).

Using memtest86+ I set my ram at 666mhz, using a x2 multiplier (333x2), then did another test with the same 666mhz using a x2.5 multiplier (266x2.5). The first test cleared more than a minute faster than the latter test even tho ram was set at the same speed. For the tests I used two different cpu multipliers to get the exact same cpu clock between tests.

 

[leandrodafontoura]

Nowadays this term is used for cpu/memory overclocking. If the memory runs at the speed of the Front side bus, then it is synchronous, else it is not. Ex.:

a core2duo with a 1066Mhz FSB means 4x266Mhz. Synchronous ram should be 533Mhz, or 2x266Mhz. In this forum this is called a 1:1 ratio.

Say you change the ram multiplier, then it will be asynchronous as the speed will differ from the FSB speeds.

There is performance hit when ram is asynchronous from the FSB (using any other than x2 multiplier).

Using memtest86+ I set my ram at 666mhz, using a x2 multiplier (333x2), then did another test with the same 666mhz using a x2.5 multiplier (266x2.5). The first test cleared more than a minute faster than the latter test even tho ram was set at the same speed. For the tests I used two different cpu multipliers to get the exact same cpu clock between tests.

So, my FSB is 266. Does it matter if I get 533MHZ or 1066 memory? I never overclock

 

[jaquith]

Can someone please explain to me the diference? Wich one should I get, synchronous memory, or highest possible? What are benchmarks in file transfer, gaming loading and fps?

The differences is SDRAM is Synchronized with the system bus {BCLK/FSB}, Asynchronous is not.

Most ALL RAM is SDRAM and 'most' platforms 'today' benefit from DDR3-1600 CAS 8/9 RAM, and while higher Frequency RAM is 'better' for Multi-Tasking it also often adds instability unless you OC; even current AMD requires a FSB 240MHz+ <OR> CPU-NB Frequency to 2400MHz+ with DDR3-1600. In addition, 'most' current platforms both games and Apps benefit from 'more' RAM e.g. 8GB of RAM with 64-bit OS the only down side is the expense.

So the Answer depends on what CPU/Platform you are using now.

 

[leandrodafontoura]

Wich memory speed would be the best to pair with i5 2500 then? At stock settings

 

[jaquith]

Depends also on your MOBO, so

On a P67 or Z68 DDR3-1600 on anything else DDR3-1333, but get 4GB/stick density and a matched set of 2x4GB.

P67 & Z68 -> F3-12800CL8D-8GBXM ; the set can run DDR3-1333 CAS 7-7-7-21 or DDR3-1600 8-8-8-24

Everything else -> F3-10666CL7D-8GBXH DDR3-1333 CAS 7-7-7-21

--

Cheaper:

IF you'll never add another DDR3-1600 2x4GB set then P67 & Z68 -> F3-12800CL9D-8GBXL and they can run DDR3-1333 8-8-8-24

Everything else F3-10666CL9D-8GBXL DDR3-1333 9-9-9-24.