Late XP/early Vista was in the right era for all the 64-bit dual cores, and first quad cores.

What is the latest game/app you want to run on it?

I played this game with an E8400 and Q6600. The single core pefromace of the dual core processors is way more important in most games, so go with the C2D E6700.

Unless..

You want to ocverclock the Q6700, inwhich case you might be able to get 3.2GHz *and* 4 cores.

Both

Core 2 Duo E7500 @ 2.93GHz
Core 3 Duo E6700 @ 3.2Ghz

should be fine. Quad Core Q6700 @ 2.66Gz has too low clock. Unless you OC it, I would not use it.

IMO.

Single core performance is what matters for those games, everything else is secondary. Number of cores above 2 does not matter, so to answer the original question - higher frequency C2D is better than lower frequency C2Q.

Also E6700 is 2.66Ghz stock AFAIK.

I think Retronaut means the Pentium Dual-Core E6700 @ 3.2 GHz.

PD2JK wrote on 2025-08-25, 16:39:

I think Retronaut means the Pentium Dual-Core E6700 @ 3.2 GHz.

Well, in that case the question becomes what's more important - extra 1MB of cache or 250Mhz of frequency. Given overclocking is a thing my choice would probably be C2D E7500. If the motherboard is compatible with wolfdale that is...

If you can overclock E7500 up to 4500MHz, the benefit of 65nm quad cores is much less noticeable.

Dont believe any overclocking on the Dell Dimension E520. I have both the Q6700 and E6700 for my E520 but I stole a couple of caps from that motherboard for another board so cant compare, for games only I'm thinking E6700.

Yeah, in OEM machines Q6700 wins hands down.

It's a DELL machine, so I am assuming its NOT geared up for overclocking. Besides, it says that all three chips have locked multipliers, so I guess that also locks down overclocking as well.
The E520 has a CUSTOM cooler (its MASSIVE), and it's an aluminium block inside a custom shroud, blown over by a large fan, but I'm really not sure how effective it is.
The Q6700, along with being a slower clock DOES use about 30% more power at 95w, so it may prove to be a fan blaster and might be VERY noisy, which is not ideal.
I guess ONLY if I wanted to do era correct 3D rendering on the machine, would the Q6700 make sense.
I'll do a little reasearch on overclocking, its been a loooong while since I owned a Core-2 Duo machine.

Retronaut wrote on 2025-08-25, 14:49:

a Core 2 Duo E7500 @ 2.93GHz a Core 2 Duo E6700 @ 3.2Ghz […]
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a Core 2 Duo E7500 @ 2.93GHz
a Core 2 Duo E6700 @ 3.2Ghz

Is there ANY reason to go with the E7500? I'm assuming that just clock speed matters so the E6700 seems to be the best dual core CPU?
And then there is the Q6700 with 4 cores at 2.66Ghz. I am assuming most games of this era (all?) will not really make use of the extra 2 cores.

Well, the E7500 does have an extra Megabyte of cache (3 MiB vs 2 MiB). For some applications, that might give it an edge ... But no way to tell without trying it out 😀

[Edit] the E6700 is as far as I can see a "Pentium Dual-Core", which IIRC was marketed as a lower-tier spec than the Core2Duo

[Edit2] No, the E6700 is both Pentium Dual Core as well as Core 2 Duo, but the Core2Duo is 2.667 GHz, where as the Pentium Dual Core E6700 is 3.2 GHz, so which do you have? 😀

H3nrik V! wrote on 2025-08-26, 05:29:

Well, the E7500 does have an extra Megabyte of cache (3 MiB vs 2 MiB). For some applications, that might give it an edge ... But […]
Show full quote

Retronaut wrote on 2025-08-25, 14:49:

a Core 2 Duo E7500 @ 2.93GHz
a Core 2 Duo E6700 @ 3.2Ghz

Well, the E7500 does have an extra Megabyte of cache (3 MiB vs 2 MiB). For some applications, that might give it an edge ... But no way to tell without trying it out 😀

[Edit] the E6700 is as far as I can see a "Pentium Dual-Core", which IIRC was marketed as a lower-tier spec than the Core2Duo

[Edit2] No, the E6700 is both Pentium Dual Core as well as Core 2 Duo, but the Core2Duo is 2.667 GHz, where as the Pentium Dual Core E6700 is 3.2 GHz, so which do you have? 😀

Yeah good distinction, I didnt know there was another E6700 other than the Core 2 Duo. Now that I look at it better I see the Pentium Dual core E6700 and the Core 2 Duo E7500 are Wolfdale and as Archer57 said:

Archer57 wrote on 2025-08-25, 17:51:

If the motherboard is compatible with wolfdale that is...

I dont think that board is compatible with Wolfdale. If that is true then neither the Pentium Dual core E6700 or Core 2 Duo E7500 wouldnt work.

It was a while ago when I found the processors for my machine but I do remember reading something that said the Core 2 Extreme X6800 or the Core 2 Extreme QX6800 were the fastest that board would support. Both of those were expensive and harder to find so I picked up the Core 2 Duo E6700 and the Core 2 Quad Q6700 instead.

I'm having to wait a couple of days, as I have had to change plans with this build. The custom cooler that DELL made for this machine seems to be the ONLY cooling solution I have at hand
As its so absolutely massive, I believe it's plastic shroud would block the cooler of the 8800 GTX I planned to use in this machine. But thats not the only issue...

I perched the stock Coolermaster cooler I have onto the CPU with thermal paste, and connected it to the motherboard using dupont connectors as the Dell connector is... non standard and that got the CPU cooler working
I rotated the cooler as its just paste and gravity holding it in place and I plugged in the 8800 GTX and well, now it has no graphics from that card (it was previously working).

To be candid I did power up the 8800 GTX for a short while WITHOUT the extra power cables attached and it squealed very loudly.
When I realised my mistake i plugged in the power cables and turned it on and poof, nothing.
However, these scenario was something that ASUS had anticipated, hence the speaker warning, although I wish I had NOT done it, I cant see giving the card less power for 10 seconds would have killed it.
Did this stress this boards caps, maybe, but again, I can't see that killing it....

Anyway, another Vogon suggested a different tack with the graphics card, to go for a SIX year newer card, a 750GTX as it uses 65W rather than 150w AND is actually more powerfull
It also comes in short versions, so I found a 750Ti for £28 and that should arrive tomorrow. I shall test then and see if it was JUST the 8800 GTX that had something go poof.

I now also have the ORIGINAL cooler here, the aluminium blocked one (£1.89! in Ebay) and then someone on Reddit mentioned there is a Copper heat-pipe model and indeed there is!
That is now ordered (£8.90) so that would I guess open up the possibility of overclocking. I need to get a stable test setup, with video of course before I can test out all of these various CPU's

The E6700 @ 3.2Ghz was sold to me as a CORE 2 Duo, but it was so cheap, that if it is not, I wont hassle the vendor.

I'm not sure if I would go down the overclocking route, its not something I had originally planned for this machine. I guess I can try it if its possible via software.

what motherboard has the dell got? it seems the Dimension E520 came out around 2006, some boards around this era are not the best for higher powered parts as they will be limited by cpu choice due to lack of bios updates and even more so if its 1066fsb, the later wolfdale cpus (pentium E6700) most likely wont have support unless dell kept up with the bios updates which i highly doubt, so you may be limited to conroe and kentsfield so you may have to settle for a core 2 E6700 instead,

also boards from around this time might be pci-e 1.0 so may only support up to pci-e 2.0, meaning the 750ti wont work as its pci-e 3.0, for £28 im guessing you got a 4gb from CeX, i was looking at one at a local store a couple of days ago as it seems like a good deal, just checked and they are now all out of stock 🙁

anyway ive got an MSI P4M900M2 from 2005/2006 and have issues with all of the above, i tried updating microcode for later wolfdale cpus but encountered the speedstep bug, which meant the cpus would run at half multiplier at 1.2ghz, so im just gonna settle for what it can officially support.

as for gpu i tried out a 640gt which is pci-e 3.0 and i got a blank screen, as the board is pci-e 1.0 it will only support gpus up to pci-e 2.0, i had the 640gt lying around and figured is a good choice as its on par with a 9800gtx and a modern card will draw less power and reduce heat. i think the gtx580 is the limit for this board, i went with a gtx460 gs which is more powerful than the 640gt.

if you want a board for overclocking go for a gigabyte, ive been using a GA-G31M-ESL2 for the last 7yrs, its a basic board but will support all 1333 core2/quads, i managed to overclock a low end E5400 from 2.6ghz to 4.09ghz, which is a 1.5ghz increase and it hasnt burnt out yet. 🤣

DudeFace wrote on 2025-08-28, 15:42:

what motherboard has the dell got? it seems the Dimension E520 came out around 2006, some boards around this era are not the bes […]
Show full quote

what motherboard has the dell got? it seems the Dimension E520 came out around 2006, some boards around this era are not the best for higher powered parts as they will be limited by cpu choice due to lack of bios updates and even more so if its 1066fsb, the later wolfdale cpus (pentium E6700) most likely wont have support unless dell kept up with the bios updates which i highly doubt, so you may be limited to conroe and kentsfield so you may have to settle for a core 2 E6700 instead,

also boards from around this time might be pci-e 1.0 so may only support up to pci-e 2.0, meaning the 750ti wont work as its pci-e 3.0, for £28 im guessing you got a 4gb from CeX, i was looking at one at a local store a couple of days ago as it seems like a good deal, just checked and they are now all out of stock 🙁

anyway ive got an MSI P4M900M2 from 2005/2006 and have issues with all of the above, i tried updating microcode for later wolfdale cpus but encountered the speedstep bug, which meant the cpus would run at half multiplier at 1.2ghz, so im just gonna settle for what it can officially support.

as for gpu i tried out a 640gt which is pci-e 3.0 and i got a blank screen, as the board is pci-e 1.0 it will only support gpus up to pci-e 2.0, i had the 640gt lying around and figured is a good choice as its on par with a 9800gtx and a modern card will draw less power and reduce heat. i think the gtx580 is the limit for this board, i went with a gtx460 gs which is more powerful than the 640gt.

if you want a board for overclocking go for a gigabyte, ive been using a GA-G31M-ESL2 for the last 7yrs, its a basic board but will support all 1333 core2/quads, i managed to overclock a low end E5400 from 2.6ghz to 4.09ghz, which is a 1.5ghz increase and it hasnt burnt out yet. 🤣

Pci-e 3 cards work just fine in pci-e 1 boards. There probably are some other compatibility issues which prevented it from working in your case. There were a few of those in early times of pci-e.

I have a couple of GTX660 cards, i use one with G31T-M3 board, another one i've recently plugged into A8N32-SLI Deluxe and it worked without issues. In both cases - pci-e 1.

Retronaut wrote on 2025-08-25, 14:49:

Hey, I am part way through trying to get a kerb sids found Dell Dimension E520 buffed up to be an XP gaming machine. =https://yo […]
Show full quote

Hey, I am part way through trying to get a kerb sids found Dell Dimension E520 buffed up to be an XP gaming machine.
=https://youtu.be/XEbO5vNhAfAI have the ... lick here)

Apart from having issues with no GFX in the machine, and the custom heatsink being a PITA, I have a quandary as to which CPU to use in it....

To hand I have....
Its original Core 2 Duo @ 1.86Ghz
a Core 2 Duo E7500 @ 2.93GHz
a Core 2 Duo E6700 @ 3.2Ghz
a Quad Core Q6700 @ 2.66Gz

Bear in mind, the machine is aimed at later stage Windows XP gaming, I have another machine from the beginning of the XP era, with a suitable spec for that time.

Is there ANY reason to go with the E7500? I'm assuming that just clock speed matters so the E6700 seems to be the best dual core CPU?
And then there is the Q6700 with 4 cores at 2.66Ghz. I am assuming most games of this era (all?) will not really make use of the extra 2 cores.

All viewpoints welcome 😀

Check out the single-core CPU benchmarks on Google. Then just pick the one with the lowest wattage — that’s the smartest choice.

Archer57 wrote on 2025-08-28, 16:36:

DudeFace wrote on 2025-08-28, 15:42:

what motherboard has the dell got? it seems the Dimension E520 came out around 2006, some boards around this era are not the bes […]
Show full quote

what motherboard has the dell got? it seems the Dimension E520 came out around 2006, some boards around this era are not the best for higher powered parts as they will be limited by cpu choice due to lack of bios updates and even more so if its 1066fsb, the later wolfdale cpus (pentium E6700) most likely wont have support unless dell kept up with the bios updates which i highly doubt, so you may be limited to conroe and kentsfield so you may have to settle for a core 2 E6700 instead,

also boards from around this time might be pci-e 1.0 so may only support up to pci-e 2.0, meaning the 750ti wont work as its pci-e 3.0, for £28 im guessing you got a 4gb from CeX, i was looking at one at a local store a couple of days ago as it seems like a good deal, just checked and they are now all out of stock 🙁

anyway ive got an MSI P4M900M2 from 2005/2006 and have issues with all of the above, i tried updating microcode for later wolfdale cpus but encountered the speedstep bug, which meant the cpus would run at half multiplier at 1.2ghz, so im just gonna settle for what it can officially support.

as for gpu i tried out a 640gt which is pci-e 3.0 and i got a blank screen, as the board is pci-e 1.0 it will only support gpus up to pci-e 2.0, i had the 640gt lying around and figured is a good choice as its on par with a 9800gtx and a modern card will draw less power and reduce heat. i think the gtx580 is the limit for this board, i went with a gtx460 gs which is more powerful than the 640gt.

if you want a board for overclocking go for a gigabyte, ive been using a GA-G31M-ESL2 for the last 7yrs, its a basic board but will support all 1333 core2/quads, i managed to overclock a low end E5400 from 2.6ghz to 4.09ghz, which is a 1.5ghz increase and it hasnt burnt out yet. 🤣

Pci-e 3 cards work just fine in pci-e 1 boards. There probably are some other compatibility issues which prevented it from working in your case. There were a few of those in early times of pci-e.

I have a couple of GTX660 cards, i use one with G31T-M3 board, another one i've recently plugged into A8N32-SLI Deluxe and it worked without issues. In both cases - pci-e 1.

i forgot to mention its not always the case and may depend on the board/chipset, the msi board i mentioned has a VIA chipset and seems to have the same issue with pcie 3.0 as the VIA asrock boards, also forgot to mention the GA-G31M-ESL2 im using has the gt640 which is pcie 3.0 though the G31 chipset supports pci-e 1.1, also if the previously working 8800gtx is having issues it could be board/PSU related and might not have enough juice to power the card.

I had this same dilemma recently, I ended up using a Q6600 overclocked to 3.33GHZ, I paired it initially with a GTX750, I later upgraded to a GTX950.
I then proceeded to never use the machine, 🤣. Per my usual.

I have a Dell G45M03 motherboard modded to run a 771 Xeon X5470. A sticker on the CPU, a BIOS mod for the needed microcode, and disabled higher C states in the BIOS. It's the only Core 2 config I have around and I thought a Yorkfield 12MB would be nice.