Have you ever taken public transit? Sometimes you get off one bus and straight onto another. That's syncronous.
On Sunday you get off a bus and spend more time waiting than you do riding, that's async.
And these 'schedules' (cycles) correspond to the RAM speed and FSB? So,
If the FSB > RAM speed
Nothing in the queue. //Is this true?
Also, if the FSB != RAM, is it possible to overflow something with large amounts of data? Is this hardly even a concern? As an example, I am getting the Barton 2600. If PC2700 and PC3200 are basically the same price, do I care which I get?
<b>SYNC = Same speed on both side of the chipset (northbridge).
AMD Barton 2500+ 333MHz FSB(166MHz * 2) <-> northbridge <-> DDR333 RAM (166MHz * 2)
P4C 2.8GHz 800MHz (200MHz * 4) <-> northbridge <-> DDR400 RAM (200MHz * 2)
<b>ASYNC = Different speed on both side of the chipset (northbridge)
AMD Barton 2500+ 333MHz FSB(166MHz * 2) <-> northbridge <-> DDR266 RAM (133MHz * 2)
Usually people want to go SYNC, since it ensure that the data transferred from both side of the northbridge will not have to "wait" or be queued in buffers. This can degrade performance. But it depends on chipset architecture, some chipsets can handle the speed mismatch with less problems. I know that nForce2 chipset performs well in SYNC mode but have some proble mwith ASYNC mode.
But, for examble, if you have an old CPU and memory and want to get a LOW cost upgrade. You might only buy a new CPU with higher FSB and run your system in ASYNC mode without a problem. But, you would not get all the performance of your CPU, since it would probably have to wait for the memory to catch up.
The best setup is MEMORY speed higher or equal to CPU FSB. So, the CPU, will never wait for the memory.
But don't forget 99% of the time, users tends to keep FSB/RAM speed in SYNC. I will stop there, because we talk a lot about this issue. Because, when you overclock, you often play with the FSB/RAM speed to get the most of your setup. I hope this post helped you understand SYNC/ASYNC issue.
If you're so willing to have the better, you buy the PC 3200 and overclock the FSB or underclock the RAM if you're not comfortable wiyh the idea of overclocking or both(let's say a sync clock of 185Mhz. Just go for the sync mode. Actually today's RAM is called "Syncronious Dynamic Random Access Memory'(SDRAM) and "Double Data Rate" for DDR and gets to DDR SDRAM. But let's focus on "Syncronious". This actually means the Ram is in sync mode with the FSB, meaning the wait states have been eliminated. Why regress from SDRAM to DRAM? The transition was made almost 10 years ago. 10 years of regress, who wants that?
That's why you want sync mode.
That was a great explanation, and the one I was looking for. I appreciate all of the input. ChipDeath, thanks...I had also wanted to know if Faster RAM would perform equal to or worse than the slower RAM, and your response was ideal. Thanks all!