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Will the cache size make this CPU a no go?

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February 18, 2007 4:17:58 AM

I am trying to upgrade the CPU on an older computer with an Intel d845ept2 mobo, and I came across a P4 2.8 533MHz 1MB cache at a very good price. Problem is, I referred to Intel's website and it says the top CPU for this mobo is a P4 2.8 533MHz with 512 KB cache. Since I kinda sorta already agreed to buy the CPU, I'm really hopeful that it will work? :? Will the cache size cause any problems? The Intel page re: supported CPUs is here:

http://www.intel.com/support/motherboards/desktop/d845e...

Thanks!

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February 18, 2007 4:49:08 AM

Quote:
I am trying to upgrade the CPU on an older computer with an Intel d845ept2 mobo, and I came across a P4 2.8 533MHz 1MB cache at a very good price. Problem is, I referred to Intel's website and it says the top CPU for this mobo is a P4 2.8 533MHz with 512 KB cache. Since I kinda sorta already agreed to buy the CPU, I'm really hopeful that it will work? :? Will the cache size cause any problems? The Intel page re: supported CPUs is here:

http://www.intel.com/support/motherboards/desktop/d845e...



Thanks!


Should be a non-issue. Have you checked for any BIOS updates? That may have been the top dog when they built the board and they never updated the literature.


There's a P08 BIOS here
February 18, 2007 4:49:21 AM

Quote:
I am trying to upgrade the CPU on an older computer with an Intel d845ept2 mobo, and I came across a P4 2.8 533MHz 1MB cache at a very good price. Problem is, I referred to Intel's website and it says the top CPU for this mobo is a P4 2.8 533MHz with 512 KB cache. Since I kinda sorta already agreed to buy the CPU, I'm really hopeful that it will work? :? Will the cache size cause any problems? The Intel page re: supported CPUs is here:

http://www.intel.com/support/motherboards/desktop/d845e...

Thanks!


The one megabyte cache is a Prescott and the 512 megabyte cache is a Northwood. If the motherboard does not support Prescott's then you should look on the motherboard manufacturer for a bios flash. When the socket 478 Prescott came out, older motherboards needed a bios flash.

For example, my current new AM2 motherboard will support the AM2+ quad core processors in a year or so, but it will need a bios flash. That's not too hard to do, but screwing it up can be as serious as screwing up installing the CPU itself. Since you're okay with installing the CPU, check for bios updates and see if you can use that CPU. Get a CPU cooler rated for the hotter socket 478 Prescotts as well. Don't use an old Northwood cooler.

You can find out how to check your bios here:

http://www.intel.com/cd/channel/reseller/asmo-na/eng/pr...

I'm guessing that it doesn't have a bios that supports a Prescott, so you should get another board that will. There are still some inexpensive socket 478 boards around that would work.
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February 18, 2007 4:52:45 AM

Quote:
I am trying to upgrade the CPU on an older computer with an Intel d845ept2 mobo, and I came across a P4 2.8 533MHz 1MB cache at a very good price. Problem is, I referred to Intel's website and it says the top CPU for this mobo is a P4 2.8 533MHz with 512 KB cache. Since I kinda sorta already agreed to buy the CPU, I'm really hopeful that it will work? :? Will the cache size cause any problems? The Intel page re: supported CPUs is here:

http://www.intel.com/support/motherboards/desktop/d845e...

Thanks!
It's not a matter of the cache size, it's that the new CPU(1mb) is a Prescott core. Many older motherboards don't support Prescott CPU's. Prescott called for a new VRM spec(different voltage graduations), and the capacitors and VRM's had to be able to handle the increase heat and current draw of the newer CPU. You can try it, and it will likely work, but the motherboard could possibly die a quick death... or die over several weeks/months. It could also work fine for years, but only you know if you're willing to take that chance. GL :) 
February 18, 2007 4:58:49 AM

I could do a bios update. I looked into it today but it required a floppy disk, and I haven't used a floppy disk in ages and don't have any on hand. I suppose I could just burn the file to a CD and it would get booted just the same, right?
February 18, 2007 5:05:35 AM

Quote:
It's not a matter of the cache size, it's that the new CPU(1mb) is a Prescott core. Many older motherboards don't support Prescott CPU's.


Ah. That explains it. I was wondering why this CPU, which seemed to have better specs, would be so much cheaper than the ones with 512 cache. If I am understanding correctly, it's because the northwood represents the highest upgrade for a lot of people with a certain mobo, and the prescott is probably a lower end CPU for mobos that can accommodate it.
February 18, 2007 5:29:27 AM

Quote:
It's not a matter of the cache size, it's that the new CPU(1mb) is a Prescott core. Many older motherboards don't support Prescott CPU's.


Ah. That explains it. I was wondering why this CPU, which seemed to have better specs, would be so much cheaper than the ones with 512 cache. If I am understanding correctly, it's because the northwood represents the highest upgrade for a lot of people with a certain mobo, and the prescott is probably a lower end CPU for mobos that can accommodate it.Yes and No . Northwood came first. Then after a few years-Intel tried to improve on it, by adding 512k more L2 cache, increased from 20 to 31 pipelines(which theoretically allows for higher clock-speeds)better prefetchers, better hyper-threading and new instructions(SSE3)plus other so-called improvements. Unfortunately increasing the pipeline from 20 to 31 stages caused a large drop in IPC(instructions per cycle)...which the extra L2 was supposed to help overcome, but the end result was a slower, hotter processor...that almost everyone grew to hate. A lot of enthusiasts moved back to Northwood(if they could), making the lower supply of N/woods more expensive(also Prescott is manufactured on 90nm vs. N/woods 130nm...which makes the chip cheaper to produce)along with N/wood being discontinued. Basically, Prescotts are okay, if you have decent cooling...and want top overclock...as they can reach higher clock-speeds ..negating the lower IPC. Some apps,( for example.. video encoding) are faster with Prescott, due to the larger cache. Sorry for the long post. :?
February 18, 2007 6:08:33 AM

Quote:
Then after a few years-Intel tried to improve on it, by adding 512k more L2 cache, increased from 20 to 31 pipelines(which theoretically allows for higher clock-speeds)better prefetchers, better hyper-threading and new instructions(SSE3)plus other so-called improvements.


Just to make sure there isn't a misunderstanding, the CPU does not have multiple pipelines. What he is refering to is that a pipeline has stages that do different parts of the instruction/calculation. The 20-31 change was a change in the number of stages. As the number of stages goes up, the speed at which each stage can go increases. However, it is also more difficult to keep the pipeline completely busy, which decreases efficiency.
February 18, 2007 6:32:06 AM

The added stages also require more memory band width. With the 20 stages, but only a 133 (quad pumped) fsb, the woodyb was a bit bandwidth starved, the prescott, with 31 (35?) stages layed down and died by comparison.
The NorthwoodB is a better performer than a 133 fsb prescott.

To the OP. Your board was not designed to give either the total current, or the variable voltage that prescott uses. You probably wont even be able to boot with that chip.
February 18, 2007 6:41:29 AM

Quote:
Then after a few years-Intel tried to improve on it, by adding 512k more L2 cache, increased from 20 to 31 pipelines(which theoretically allows for higher clock-speeds)better prefetchers, better hyper-threading and new instructions(SSE3)plus other so-called improvements.


Just to make sure there isn't a misunderstanding, the CPU does not have multiple pipelines. What he is refering to is that a pipeline has stages that do different parts of the instruction/calculation. The 20-31 change was a change in the number of stages. As the number of stages goes up, the speed at which each stage can go increases. However, it is also more difficult to keep the pipeline completely busy, which decreases efficiency.Yes, i sort of tried to correct that a few lines down:

Quote:
Unfortunately increasing the pipeline from 20 to 31 stages caused a large drop in IPC(instructions per cycle)...which the extra L2 was supposed to help overcome, but the end result was a slower, hotter processor...that almost everyone grew to hate.


:wink:
February 18, 2007 7:23:05 AM

Correct me if I'm wrong, but from what i've heard the northwood performs better than the prescott (for socket 478) anyway so this is really a non-issue. correct?

Edit: Didn't read all the posts carefully, i guess one or two people already mentioned this. :wink:
February 18, 2007 12:27:14 PM

Luckily, I was able to get out of purchasing the Prescott CPU amicably. I can now pursue a Northwood chip armed with some good knowledge. Thanks for the tips, everyone.
February 18, 2007 6:19:01 PM

http://www.ewiz.com/detail.php?name=P2.8-533
A 2.8GHz Northwood for ~$67, the most reasonable chip you could get for your board because higher clocked Northwoods are way too exatic in price for the performance they add and lower clocked ones are just not what is expected nowadays, however, if you've been stuck with some 2.0 or 2.4GHz celeron until now, even a 2.66GHz Northwood will be worth for ~$10 less, it will still perform like a 2.8GHz Prescott in most cases:
http://www.ewiz.com/detail.php?name=P2.66_533
February 18, 2007 9:20:04 PM

Quote:
http://www.ewiz.com/detail.php?name=P2.8-533
A 2.8GHz Northwood for ~$67, the most reasonable chip you could get for your board because higher clocked Northwoods are way too exatic in price for the performance they add and lower clocked ones are just not what is expected nowadays, however, if you've been stuck with some 2.0 or 2.4GHz celeron until now, even a 2.66GHz Northwood will be worth for ~$10 less, it will still perform like a 2.8GHz Prescott in most cases:
http://www.ewiz.com/detail.php?name=P2.66_533


Yes, I have a P4 2.8 Northwood 533fsb in my second PC with a D865PERL mobo and an AIW Radeon 9800 Pro. I thought of upgrading that one last time to a 3.4 Northwood and an X1950 Pro AGP, but the Northwoods are very expensive past 2.8. Of course, I could go the Prescott route, but I gave away an ASUS P5RD1 board with a P4 630 because it overheated and I went back to my Northwood setup in that PC. If I lived in Alaska, I might need a space heater, but not here in Texas!

I think the only people who love Prescotts are the guys who designed and marketed them. In games, in most applications, a Northwood performs better than a Prescott that's clocked 200 megahertz higher, so that 630 only had EM64T going for it, and I wasn't using a 64 bit OS, so the only reason for that upgrade was the PCIe slot, as it turned out the only dual core that motherboard would support was an 805.
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