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Ram, FSB and CPU
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Jinkazuya
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7. November 2009 @ 16:37 |
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I am not sure if this would be appropriate to create a new thread of asking things similar to each other, but it would be best, in my opinion to create a new thread in fear of making things cluttered and complicated.
Well...When selecting the RAM, how can you determine the max ratio and max speed of the CPU that interacts with the memory? For instance, if I have the CPU with FSB 800MHz(which is old or ancient CPU back to P4), and I want the max ratio of 4:4 of the speed used to communicate between the CPU and the memory, that's via the FSB, how do I know which RAM to buy? Should I go for ram with the same MHz, which is 800MHz? Or half of it, which is 400MHz and why? Because P4 800MHz is quad pumped, which is 200MHz for the FSB, and the DDR2 ram is double pumped, and a 800HMz DD2 RAM should be running with two chips of DDR with 400MHz.
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AfterDawn Addict
4 product reviews
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7. November 2009 @ 21:59 |
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Originally posted by Jinkazuya:
I am not sure if this would be appropriate to create a new thread of asking things similar to each other
No it isn't, try to stick to one thread in future :P While it may unclutter your own threads, it clutters up the threads list for other people's threads. This isn't forum regulation to my knowledge, it's just something I prefer people to do.
800mhz FSB is old news, but modern CPUs of today still use it, the Pentium Dual Core E5000 range for example. If you have a CPU with a low FSB like 200(800), then there is no need for RAM of greater than 800mhz speed. Here's why:
The minimum memory multipler is 2, and the maximum memory multiplier of 4 (this goes for all Core 2 based systems).
Thus:
200mhz FSB - memory speed 400mhz (PC3200) - 800mhz (PC6400)
266mhz FSB - memory speed 533mhz (PC4200) - 1066mhz (PC8500)
333mhz FSB - memory speed 666mhz (PC5300) - 1333mhz (PC10666) (tends not to exist for DDR2)
400mhz FSB - memory speed 800mhz (PC6400) - 1600mhz (PC12800)
The intermediate multipliers vary depending on what strap you use (I won't go into that just yet), but ultimately, the mins and maxes are most important.
Of course, if you overclock a CPU the minimum required memory speed rises. However, buying anything less than 800mhz DDR2 tends to be a waste of time these days as it rarely costs any less. With a 200mhz FSB CPU, you can go all the way to 400FSB with even 800mhz memory, that's a 100% overclock. Very few CPUs can manage that much, the only one I can name being the Pentium Dual core E2140 (1.6 to 3.2).
Take my situation. Suppose you have a 333mhz FSB CPU, and want to overclock it a little bit, but keep the memory at rated speed, and as fast as possible. You can buy PC8500 memory which is 1066mhz, and get the CPU to a nice round 400mhz FSB. To do this, you need to use a 2.66 memory multiplier. Fortunately for strap D (when your CPU is at 400mhz FSB or higher), such a memory multiplier does exist.
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Jinkazuya
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8. November 2009 @ 00:39 |
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I will keep all my question in one thread but what I am afraid is if too many people create new threads, my thread would be left unanswered.
However, when you talked about multipler by 2 and by 4, min and max, you mean we take the base clock of the FSB multiply by 2 for min and 4 for max? For example, Premium 4 of intel, and it supports FSB of 800HMz, and because it is quad pumped, so the base clock is 200MHz. So if we go for ram between DDR, DDR2 and DDR3, we should get either 400MHz or 800HMz?
What is the advantage of getting the 400MHz or 800MHz?
Will that go the same for all kinds of rams(DDR, DDR2 and DDR3)?
(if base clock is 200MHz, if we get DDR, we get 400MHz or 800MHz, same goes for DDR2 and DDR3?)
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AfterDawn Addict
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8. November 2009 @ 01:43 |
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Essentially, in the BIOS when you overclock a CPU, along with setting the actual FSB speed, you set the memory multiplier, which has various options between 2 and 4 - typically 2, 2.66, 3.33 and 4. To get 800mhz RAM on a 200FSB you need 4x, to get 1066mhz RAM on a 400FSB you need 2.66x, and so on.
If you had 400mhz RAM you could not use a CPU with a FSB any higher than 200, nor could you overclock it.
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Jinkazuya
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8. November 2009 @ 19:41 |
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Yes that makes sense.
But the question I would like to ask is how I could get the most accurate, appropriate and proper ram that works efficiently with the FSB? Forget about the overclocking stuff just as by now. Because there are too many rams with latency like 3-3-3 9 or 3-4-6, stuff as such and even some rams with the clock speed that don't match the FSB, SO THAT's the problem. A lot of people talk about 1:1 ratio or 3:4 ratio and so on, some of them said 1:1 ratio is the most efficient but some others said different things.
So basically the questions I have boil down to these, and really hope Sammorris, you could spare a few minutes with me, detail what is required to make the FSB work efficiently with the RAM.
1) Latency? What does it have to do with the FSB and CPU?
2) Ratio. I thought 1:1 would be the best, but some people said async ratio would work better. So hope u could clarify the mystery here.
3) what is the timing? That's 3-3-3 9 as such.
4) When choosing the ram DDR, DDR2 or DDR3 with same rated speed such as 600MHz(this is just something I made up), what is the difference between three of them? Will one be faster than another?
5) Well...with a FSB that's 1200HMz(something I made up too), should I buy the ram 1200HMz? Or I have to get the real speed(clock rate) of the FSB(Intel divide by 4, AMD divide by 2), so the system clock(real clock rate of FSB) is 1200 / 4 = 400MHz, and then buy the ram 400MHz that matches it? Or double it up to 800MHz or slightly higher than 400MHz, which is 533HMz?
These are what I am confused about...AND I hope you could help me out with this before I decide to get the real thing done in order to assemble my PC.
This message has been edited since posting. Last time this message was edited on 8. November 2009 @ 21:18
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AfterDawn Addict
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11. November 2009 @ 12:45 |
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Long story short, buy the RAM that makes sense. For core 2 chips, you go with PC6400 for midrange or cheap builds, PC8500 for high-end builds. PC6400 RAM is typically CAS4 or CAS5, PC8500 RAM is typically CAS5. For i5 chips, you go with PC12800, CAS9 is cheap but perfectly fine to use.
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