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LGA 775 CPU compatibility

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First post, by nd22

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I am creating this topic in order to clarify the compatibility between different chipsets/motherboards with different generations/revisions of LGA775 processors. This is more like a general topic and will include memory compatibility and also when necessary storage/video card compatibility.
1. For the first problem let's take the first generations of Intel chipsets for LGA775: 915p/925x/925xe - they support Prescott all revisions and do NOT support dual cores such as Pentium D, but do they support Cedar mill - the last Pentium 4 revision with the best - lowest - power consumption ? Another problem here is the memory: on Wikipedia the maximum amount is 4gb - this is the maximum addressable limit of the chipset meaning you have to use 1gb modules or 2gb will also work - you can put 4 2gb modules but the board will only recognize 4gb?
2. Second problem: Intel 945p/955x support all Pentium 4/D but some motherboards support Core 2 duo also. 945p can address 4gb of ram maximum or did someone tried more?
3. Third problem: Intel 965p/975x can take first Core 2 duo revision with 1066FSB only or they can take the last models with 1333FSB; dual cores and quad cores have different revisions - are they all supported or only certain revisions?
4. Fourth problem: Intel P35/X38 have the broadest support - practically all LGA775 CPU are supported by these boards - are there any exceptions?
5. Fifth problem: Intel P45/X48 support all Core 2 duo all revisions but probably not the early Pentium4/D - are any boards that can take all LGA775 CPU with these chipsets?
6. Sixth problem: others chipsets from Intel such as 865/875
7. Seventh problem: non Intel chipsets - NVIDIA 600/700 series
8. Eight problem: non Intel chipsets - VIA PT800/900 series

The problem is not limited to the CPU/chipset but also to the motherboard manufacturer - late BIOS versions if released means more support sometimes!

Reply 1 of 33, by nd22

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I will put here the first example - a build designed to take on Windows Vista; targeted period: January 2007
CPU: Q6600 cooled by cooler master 212x
RAM: 4*2gb Corsair DDR2 - 800
GPU: Ati Radeon X1950XTX * 2
Motherboard: Abit AW9D-MAX
SSD/HDD/ODD: -/750gb from WD/unknown
PSU: Corsair RM850i
Q6600 is supported out of the box; next to test was E8400 C0 revision which also passed followed by E8400 E0 revision also confirmed to work just fine; Q9650 E0 - only revision! - not supported, the board enters a continuous restart loop!
Another problem observed during testing: VRAM is really important: Ati radeon RX580 8GB - the board simply refuses to start with these particular video card or even if it starts on the POST screen a message is displayed that overclocking has failed loading defaults - even after loading the defaults values Windows is highly unstable and crashes often at any GPU intensive application such as 3dmark 2006! Radeon 4890 1gb tested and working just fine! GTX 960 2gb tested - EVERYTHING OK!
SSD - all from Intel work out of the box including: 330/335/540/545 series with capacities ranging from 180gb to 512gb.
HDD: everything up to 2000gb is correctly recognized - they are all WD - have not tested capacities over 2000gb!

Reply 2 of 33, by chinny22

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Don't forget about the LGA 775 Xeons,
X3000, 3100, 3200, 3300 CPU's have a very good chance of been supported out of the box if the motherboard supports the Pentium equivalents.
(confirmed on my Asus P5KPL-AM and Asus P5N-D Rev 1.02G motherboards)

If no direct equivalent exists it will come down to the BIOS.

LGA 771 is also an option with a mod
https://www.delidded.com/lga-771-to-775-adapt … d-compatibility

Reply 3 of 33, by cyclone3d

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P45 should support ALL LGA775 CPUs.

Looking at the CPU support list for the Gigabyte EP45-UD3P motherboard that looks to be the case:
https://www.gigabyte.com/us/Motherboard/GA-EP … ort#support-cpu

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Reply 4 of 33, by agent_x007

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Ad. 1.
Old "first gen" chipsets for LGA 775 should support Prescott/Gallatin no problem, however getting SpeedStep, VT-x, and/or 64-bit support may be an issue for oldest ones.
If board doesn't have proper BIOS, some options may not be available (usually OEM ones).
Cedar Mill support is PCB thing (VRM spec), newer boards based on 925X can support it, example : LINK.
4GB+ support isn't possible on those (chipset does not support memory Remap function).
Getting 2x2 GB to work may be possible, but again, it all comes down to BIOS (and how good it is with picking timings on AUTO for unsupported memory capacities).

Ad. 2. Getting 8GB+ memory requires expensive RAM sticks (Intel compatible ones).
It's far better to buy proper DDR3 LGA 775 board than to buy them.

Ad. 3. If 975X board can work with 1333MHz when OC, it does support CPUs with 1333MHz FSB (it's simply marketing thing to not say older stuff also supports this).
All Quad Cores should be supporteed if one of them is (but this is PCB/BIOS limitation to overcome, so some boards can do it, while some don't)

Ad. 4. X38/X48 do not support Gallatin (you can try to add uCode support but VRM specs can't changed). 16GB support (only 4x Dual Ranked modules).

Ad. 5. My Rampage supports Pentium Extreme 955 no problem, same goes for Cedar Mill : https://valid.x86.fr/ffqup6.
Prescott support on X48 : LINK

Ad. 6. Can do 4GB RAM and support AGP. Interesting for having 64-bit on AGP cards, but that's pretty much it. Can make good Win98 setups (if ISA isn't required), limited to DDR1 RAM type.

Ad. 7. Worse OC than Intel, on DDR2 don't limit DRAM to twice FSB clock (it can go lower).
Are required for SLI support (officially), some like Xeon's some don't, may get quite hot under load, mixed bag experience. Don't use unless you have to.

Ad. 8. SUCK at OC (high multi [fully unlocked best] and low FSB base, are requirements for OC).
Usually are Vcore/NB Voltage locked (hard mods needed)
Support only GPUs with PCi-e up to 2.0 version. No NVMe support (same goes for GPUs with PCIe 3.0). 4GB RAM limit, can do AGP when needed and support Win98.
Usefull in limited cases, not that great for general use.

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Reply 5 of 33, by Fujoshi-hime

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Are there any issues with Win98 or ME and 775 CPUs? I've seen some YouTubers use a few some 775 CPUs on 98 but I'm not sure if there are any compatibility pitfalls.

I'm asking because I picked up an Asrock 775i65G (Not the R3.0, but I think they should be nearly the same?) for building a 'powerful 98 machine' but I'm wondering if there's any CPU's I need to avoid. (Other than 98 being single core, so it'll ignore any additional cores in a system)

Reply 6 of 33, by chinny22

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Double check your motherboard against the list here, MB's like the AsRock 775i65GV have issues with their AGP port
LGA 775 Motherboards with AGP Slots

Re the CPU, as long as the motherboard supports it so should Windows as its a case of windows simply been to "dumb" to recognize the extra cores, it's no so much a case of it doesn't understand it, more it doesn't even know they exist.
As for Cache, FSB, clock speed, Windows doesn't even care about this that's the job of the bios. It's why Win98 boot disks work in systems for so long. UEFI is where Win9x starts to get confused.

Reply 7 of 33, by Fujoshi-hime

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chinny22 wrote:
Double check your motherboard against the list here, MB's like the AsRock 775i65GV have issues with their AGP port LGA 775 Mothe […]
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Double check your motherboard against the list here, MB's like the AsRock 775i65GV have issues with their AGP port
LGA 775 Motherboards with AGP Slots

Re the CPU, as long as the motherboard supports it so should Windows as its a case of windows simply been to "dumb" to recognize the extra cores, it's no so much a case of it doesn't understand it, more it doesn't even know they exist.
As for Cache, FSB, clock speed, Windows doesn't even care about this that's the job of the bios. It's why Win98 boot disks work in systems for so long. UEFI is where Win9x starts to get confused.

That's an interesting page but I'm not entirely sure all the info is accurate. That is to say, my AsRock 775i65G, not the R2.0 or R3.0 and for sure on paper and on the Asrock site it states it only supports Pentium D or lower. That said, it has Conroe Celeron 420 in it and it POSTs at least. That's how I bought it and that's def a Core 2 series chip. I've not had time to test it beyond plugging it in to POST it and ensure it survived it's way from Poland.

I've been thinking of trying to swap in a more powerful Core 2 chip to test. I can report my findings, it wouldn't be expensive, we're talking about the kinda chips that cost CAD$10-$15

Reply 8 of 33, by chinny22

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Fujoshi-hime wrote:

That's an interesting page but I'm not entirely sure all the info is accurate. That is to say, my AsRock 775i65G, not the R2.0 or R3.0 and for sure on paper and on the Asrock site it states it only supports Pentium D or lower. That said, it has Conroe Celeron 420 in it and it POSTs at least. That's how I bought it and that's def a Core 2 series chip. I've not had time to test it beyond plugging it in to POST it and ensure it survived it's way from Poland.

I've been thinking of trying to swap in a more powerful Core 2 chip to test. I can report my findings, it wouldn't be expensive, we're talking about the kinda chips that cost CAD$10-$15

If it is wrong, post an update or send a PM to the OP as he's still active here 775 based Win98 rigs are getting really popular now

Reply 9 of 33, by Fujoshi-hime

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chinny22 wrote:
Fujoshi-hime wrote:

If it is wrong, post an update or send a PM to the OP as he's still active here 775 based Win98 rigs are getting really popular now

To be clear, Asrock ALSO doesn't list a single Core 2 CPU as being supported by this mobo. So this CPU support for a Conroe and maybe others appears to be undocumented.

That said, considering all the hardware between the R1, R2, and R3 is nearly identical but for minor PCB revisions and their firmware is likely developed in paralelle, I wouldn't be surprised if the R1.0's CPU support actually matches the R3.0

Reply 10 of 33, by Warlord

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those earlyer boards that only support 775 cedarmill, have very limited support for 1st gen conroe parts, I am talking a bout the core 2s that 1st came out. they lack VRMs to handle later quadcores or even later core 2 duo. Probably highest you can put in it is 2ghz conroe

Reply 11 of 33, by Fujoshi-hime

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Warlord wrote:

those earlyer boards that only support 775 cedarmill, have very limited support for 1st gen conroe parts, I am talking a bout the core 2s that 1st came out. they lack VRMs to handle later quadcores or even later core 2 duo. Probably highest you can put in it is 2ghz conroe

So er, maybe don't go bigger than a single core Celeron 450 for my Win9X build then, huh? 😮

Reply 13 of 33, by pixel_workbench

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Depends on the board. My Asus P5Q doesn't support Celeron D processors, and wouldn't POST when I tried one, which was strange considering that it supports Pentium 4. Meanwhile, Gigabyte P45 boards with the same chipset support the Celeron D.

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Reply 14 of 33, by agent_x007

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pixel_workbench wrote:

Depends on the board. My Asus P5Q doesn't support Celeron D processors, and wouldn't POST when I tried one, which was strange considering that it supports Pentium 4. Meanwhile, Gigabyte P45 boards with the same chipset support the Celeron D.

It's not about name, it's about FSB.
Celeron Ds (and some Pentium 4s) have 533MHz FSB, and ASUS BIOS can't be set lower than 800MHz (200MHz real clock).

It MIGHT work, if you do Vcore VID mod those 533MHz CPUs (Vcore that it needs to work at 50% OC).

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Reply 15 of 33, by Fujoshi-hime

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pixel_workbench wrote:

Depends on the board. My Asus P5Q doesn't support Celeron D processors, and wouldn't POST when I tried one, which was strange considering that it supports Pentium 4. Meanwhile, Gigabyte P45 boards with the same chipset support the Celeron D.

Turns out that I was mistaken. While it was listed as an R1.0 board and the BIOS made no mention of being anything but that, 'R2.03' is silk screened on the board itself, so it's an R2.0 board which does support Conroe.

Reply 16 of 33, by nd22

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Finished testing GTX 960 4gb on Abit AW9D-MAX and i can report that VRAM is indeed a problem: the 2gb variant works fine. the 4gb crashes in many 3dmark test and also in many games but without hard locking the system! The video cards are both Asus GTX 960 strix so same manufacturer only the VRAM is different!

Reply 17 of 33, by agent_x007

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You ran RX 580 on Vista x64 ?

Are you on latest BIOS ? (LINK)
What driver you used for RX 580 on Vista ?

4x2GB of RAM may require additional NB Voltage (since more RAM = more stress on North Bridge).
Also, if BIOS doesn't correctly set timings on Auto (that goes for both 1-st and secondary/tertiary ones), system will be unstable.

Lastly, try changing Memory Remap Feature setting.

PS. I tested GTX 780 Ti on ASUS P5WD2 Premium board, worked fine with Gallatin P4EE (4x1GB RAM).

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Reply 18 of 33, by nd22

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I have a SSD with an Windows 7 installation just for testing - it's the version of Windows most compatible with newer stuff like new video cards or the like. GTX 780TI has 3gb of ram so I think problems start when you go with a 4gb video card. I am on the latest BIOS and memory remap is enabled.

1. On intel boards with 915/925x chipsets Cedar mill is supported or no? I have an Abit AA8XE and it works fine with a Pentium 4 3ghz that I got for free but it's a Prescott core - and it runs hot even at stock clocks; I am thinking about upgrading to a Cedar mill 3.6ghz but I do not know if it is compatible or no!
2. On Abit IL9 Pro 2gb modules are correctly recognized but only up to 4gb; with 4 sticks of 2gb each the board will boot just fine into memtest but it will recognize only the first 4gb; I strongly think this a chipset limitation on Intel side and not o board limitation.

Reply 19 of 33, by greasemonkey90s

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Im loving my asus commando 965p board supports all the p4s it seems and all the early conroes as well. Also has support upto e7000/8000 c2d and some 1066 quads. The only thing that honestly sucks is the 8x/4 pcie layout in crossfire kills performance not the more desired 8x/8x default when using 2 cards. The next possible negative that it more then likely cant out oc 975x boards. But i love mine.