Posted by
ryuzaki0
on from the finally-moving-forward dept.
jandrese writes "According to Cnet, Intel is finally getting around to supporting DDR SDRAM in their P4 chipsets. This is a good move on Intel's part, as they need to bring the cost of their P4 based systems down to compete with AMD, and moving away from Rambus is a good start."
(*) DDR and Rambus transfer data at both the rising and falling edge of the clock cycle, thus doubling the effective bandwidth. Bacause of that they are often reffered to as 200MHz, 266MHz, and 800MHz respectively.
Anyway, the point is that DDR has greater bandwidth than Rambus. On top of that, Rambus has a pathetically high latency. Because of that Pentium 3 systems with PC133 SDRAM outperformed their Rambus counterparts most of the time.
As an aside, Intel decided to "fix" this flaw by making Pentium 4 waste four times as much memory bandwidth as Pentium 3 -- that makes P4 highly sensitive to memory bandwidth./. linked to a very interesting article discussing the P4 architecture a while ago.
Back to the point, Pentium 4 chipset uses two channels of Rambus memory that work in parallel. That gives it 2 * 1600 = 3200MB/s of bandwidth, which is greater than a single channel of PC2100 DDR (though it still has high latency). Problem is that you need to install memory in pairs (on RIMM for each channel), and each RDRAM channel can have only two memory slots. That means you are only one upgrade away from maxing out your memory. On the contrast, each DDR channel can have up to 4 memory slots and you can upgrade one slot at a time.
Also note that NVidia Nforce does the same thing for Athlons & DDR as the P4 chipset. Of course two channels of DDR have the bandwidth of 4256MB/s).
Ahh well, I'm just grumpy b/c I convinced my mom to buy a P4T/Rambus-based P4 1.7Ghz, and now I have to ditch the Ram/Mobo/CPU to upgrade it.
I'm so tempted to say "I told you so" -- which I would have if we ever spoke.
(I'd have given her an Athlon but the dustbunnies at her place are such that I'd be afraid of her burning the place down... remember that THG vid of the flaming Athlons?)
This is about the stupidest thing I ever heard. It's like claiming that Ford makes unsafe cars because their engines fry when you drain all the oil from them. Try this: remove the heatsink and fan from your P4 and see how long it takes for it to catch fire.
-- ___
If you think big enough, you'll never have to do it.
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False. Comparing just bandwidth:
100MHz SDRAM -> 800MB/s
133MHz SDRAM -> 1064MB/s
100MHz DDR -> 1600MB/s (*)
133MHz DDR -> 2128MB/s (*)
400MHz RDRAM -> 1600MB/s (*)
(*) DDR and Rambus transfer data at both the rising and falling edge of the clock cycle, thus doubling the effective bandwidth. Bacause of that they are often reffered to as 200MHz, 266MHz, and 800MHz respectively.
Anyway, the point is that DDR has greater bandwidth than Rambus. On top of that, Rambus has a pathetically high latency. Because of that Pentium 3 systems with PC133 SDRAM outperformed their Rambus counterparts most of the time. /. linked to a very interesting article discussing the P4 architecture a while ago.
As an aside, Intel decided to "fix" this flaw by making Pentium 4 waste four times as much memory bandwidth as Pentium 3 -- that makes P4 highly sensitive to memory bandwidth.
Back to the point, Pentium 4 chipset uses two channels of Rambus memory that work in parallel. That gives it 2 * 1600 = 3200MB/s of bandwidth, which is greater than a single channel of PC2100 DDR (though it still has high latency). Problem is that you need to install memory in pairs (on RIMM for each channel), and each RDRAM channel can have only two memory slots. That means you are only one upgrade away from maxing out your memory. On the contrast, each DDR channel can have up to 4 memory slots and you can upgrade one slot at a time.
Also note that NVidia Nforce does the same thing for Athlons & DDR as the P4 chipset. Of course two channels of DDR have the bandwidth of 4256MB/s).
Ahh well, I'm just grumpy b/c I convinced my mom to buy a P4T/Rambus-based P4 1.7Ghz, and now I have to ditch the Ram/Mobo/CPU to upgrade it.
I'm so tempted to say "I told you so" -- which I would have if we ever spoke.
(I'd have given her an Athlon but the dustbunnies at her place are such that I'd be afraid of her burning the place down... remember that THG vid of the flaming Athlons?)
This is about the stupidest thing I ever heard. It's like claiming that Ford makes unsafe cars because their engines fry when you drain all the oil from them. Try this: remove the heatsink and fan from your P4 and see how long it takes for it to catch fire.
___
If you think big enough, you'll never have to do it.