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Intel 845e versus 850e. DDR266 versus 800Mhz RDRAM

Forum CPU & Components : CPUs - Intel 845e versus 850e. DDR266 versus 800Mhz RDRAM

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fern3   08-06-2002 at 12:53:17 AM

What are the pros/cons of an 845e versus an 850e based system?

How about an 850e based system with a P4 2.0Ghz with a 400Mhz FSB and 800Mhz RDRAM versus an 845e based system with a P4 2.0Ghz with a 400Mhz FSB and DDR266 RAM?

Basically, what are the pros/cons of an 800Mhz RDRAM system versus a DDR266 RAM system? Are there any scaling issues? That is, does the RDRAM based system begin to outperform the DDR266 only at higher clockspeeds?

What about the longevity of DDR versus RDRAM technology? Is picking an RDRAM based system a bad move? Will RDRAM be around in 1 year? 2 years? What are Intel's plans in the future regarding memory technology?

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TWC   08-06-2002 at 03:13:12 AM
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pc 800 rdram is faster than ddr266, but ddr333 is faster than pc800 rdram.

"I'd rather laugh with the sinners than cry with the saints."

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aufan17   08-06-2002 at 03:25:35 AM
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Remember, if you have the money, you can always get pc1066 RDRAM. It flies

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Crashman   08-06-2002 at 07:50:54 AM
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LOL, I don't think so Tim. DDR266 is ~2100MB/s, DDR333 is ~2700MB/s, PC800 is ~3200MB/s.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>

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Crashman   08-06-2002 at 07:57:47 AM
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RDRAM has higher bandwidth that DDR SDRAM. Although PC800 has the same bandwidth as DDR400, PC1066 is unequaled in bandwidth by any DDR SDRAM. SDRAM (including DDR SDRAM) usually offers a little less latency in real time, which is why DDR333 gives similar performance to PC800 on the P4 even though it has less bandwidth.

RDRAM will be around for a while yet, but eventually it will likely be replaced with Dual Channel DDR SDRAM, which will have both high bandwidth and short latency. Since these boards are not yet available, PC1066 is your best performance option right now.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>

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Chuck232   08-06-2002 at 03:08:13 PM
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But SiS is coming out with their DC DDR chipsets pretty soon actually eh? And I think DDR333 would cost less than PC1066. Put that in a DC board and you've got 5.4GB/s bandwidth with low latency.

<i>Past mistakes may make you look stupid, but avoiding future ones will make you look smart!</i>

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fern3   08-06-2002 at 08:47:38 PM
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Crashman, thanks for the info.

In order to use PC1066 RDAM, must I have a P4 with a 533Mhz FSB? I was planning on purchasing a P4-2.0Ghz with the 400Mhz FSB because it is much cheaper.

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Crashman   08-06-2002 at 08:56:13 PM
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Dual Channel PC2100 would compete directly with current Rambus technology (PC1066 for the i850E is dual channel DDR1066 Rambus at 533MHz). That is, it has the same bandwidth. As usual, going with faster DDR333 memory while at the stock 133MHz bus speed doesn't give you any more real bandwidth, becuase the CPU to Memory transfers would be limitted by the slower of the two busses. But it would give you a slight latency advantage.

The real advantage is for overclockers. If you raised your bus speed to 166MHz at a 1:1 ratio, DC DDR333 would be perfect.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>

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Crashman   08-06-2002 at 08:57:16 PM
- 0 +

To the point, 5.4GB/s memory bandwidth doesn't mean much when your CPU bus is 4.2GB/s.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>

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Chuck232   08-06-2002 at 09:12:13 PM
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Well, as Crash said, the only way you'll use the full potential of PC1066, you'll have to overclock to 133MHz FSB. That may be attainable. That's 2.66GHz... Not too high. P4 1.8A can hit that sometimes.

<i>Past mistakes may make you look stupid, but avoiding future ones will make you look smart!</i>

Reply to Chuck232
Chuck232   08-06-2002 at 09:15:10 PM
- 0 +

Well, I don't follow the AMD scene much, but is that why the DDR333 doesn't seem to help the AXPs too much? They're limited by their 133MHz DDR FSB... So if the rumour is true that they're switching to a 166MHz FSB, it could mean quite a bit more performance, if you used DDR333.

BTW, how do you figure out the CPU bus? Is it just MHz * by something?

Like to figure out the bandwidth of the 133MHz FSB for the AXP, what do you do? (I know it's 2.1GB/s)

<i>Past mistakes may make you look stupid, but avoiding future ones will make you look smart!</i>

Reply to Chuck232
Crashman   08-06-2002 at 09:41:52 PM
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You could get a 1.6A and overclock it to 2.13GHz (very reliable overclock, almost 100% of processors). Or you could get a 1.8A and overclock it to 2400MHz (very reliable overclock, over 90% of processors). Or you could get a 2.26.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>

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Crashman   08-06-2002 at 09:45:33 PM
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Figure out the bus bandwidth with simple math 133MHz x 64bits / 8 = 1064 MB/s. For DDR bus, multiply by 2. For QDR bus, multiply by 4.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>

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Chuck232   08-07-2002 at 12:46:33 AM
- 0 +

Ok thanks!

<i>Past mistakes may make you look stupid, but avoiding future ones will make you look smart!</i>

Reply to Chuck232
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