NX-Bit on Socket 478 - A Possibility?

[Tech&Music]

Recently I've been looking into two features uncommon on the Socket 478 platform: EM64T and eXecute Disable Bit. EM64T has been something that's been confirmed to be possible on Socket 478, specifically the Prescott SL7Q8 and SL7QB S-Spec CPUs are known to support it, as proven by CPU-World user xsecret, and VOGONS users agent_x007 and MrGenius.

However, eXecute Disable Bit, or NX-Bit in non-Intel-speak, has been elusive. Since Windows 8, this has been a hard CPU requirement, and despite hacks existing, updates to Windows 8 frequently break these. Windows 10 is even less hackable, given it goes through a full feature update twice a year. So running these OSes on Socket 478 long-term is neigh impossible... or is it?

Recently I discovered the SL8JX, which according to some is a Prescott Socket 478 CPU with EM64T and XD-Bit support. According to Intel's ARK website, it is a Socket 478 version of the Pentium 4 511, which is normally known as a Socket 775 CPU, and does have these mentioned features. However, hard evidence of these CPUs actually having these features, XD-Bit specifically, made me want to get a SL8JX for myself, and prove or disprove this. And in case it was true, see if Windows 10 on Socket 478 without hacks is a possibility after all.

Getting this CPU has proved to be difficult. Many sites ask big bucks for it. Some ask acceptable prices, only to then email you that they don't actually have the CPU in stock. Just yesterday, another store mailed me back with this, but they mentioned two potential replacement S-Specs they could ship. And this made me discover that these are also supposedly the Pentium 4 511 on Socket 478, but with a different stepping.

Looking at the CPU family on CPU World, this is the information on different S-Specs of the P4 511 on Socket 478 there supposedly are. In bold are the different steppings, under which the S-Specs are listed. The regular S-Specs are confirmed to be 511's on Intel's ARK, but don't take this as a hard confirmation of XD-Bit on S478 just yet. The qualification samples are not listed on the ARK. There is one that I will mention that is a bit different:

C0:
QW78
SL7D8
SL7K9
D0:
QP11
SL7E2
E0:
Q00V
SL7PK
SL88G
G1:
SL8JX

The curious case is the SL7K9. CPU World just lists it as a 2.8GHz part, like the 511, but if you look this S-Spec up on the ARK, it will show both the page for the 511 in the results, but it also shows the page of a 2.4GHz, 32-bit, non-XD Bit Prescott Socket 478 Pentium 4. It could potentially mean Intel accidentally used the same S-Spec twice, or it's an error in the ARK database. Eitherway, if you look for this CPU for testing, be sure to check clockspeeds.

Still, even though the ARK reports this, I am not 100% confident that this is a hard confirmation that XD-Bit on Socket 478 is possible, and whether these CPUs actually have it or not. Also, even if it is the case, whether every board supports it or not is another question. I know my SL7QB's EM64T feature doesn't work right with my Socket 478 boards. The crappy Lite-On HP OEM board just craps out with it, and the Gigabyte 8KNXP board I have will properly ID it as an EM64T CPU in CPU-Z, yet booting any 64-bit OS results in the computer resetting the moment it tries to enable the kernel, as far as I can tell. What exactly is causing the incompatibility here, I am not sure. Maybe something physical with the board, maybe something with the BIOS (which is fully updated). I have no idea if XD-Bit would have similar problems.

My end goal is to get a ASRock P4i945GC board for testing, as it's known to work with the SL7QB and SL7Q8 and EM64T, and it has PCI-e, which is beneficial for Windows 10, as current versions lack support for AGP Graphics. 64-bit Windows 8 or 10 might still not work, because they require the CMPXCHG16b, LAHF/SAHF, and PrefetchW instructions which the CPU might also not have. However, this should not be a problem for the 32 bit versions of these operating systems, which do require NX-Bit.

On eBay, I did find a seller from China with an ad for the SL7E2, SL7PK, and SL7D8 S-Specs, for just a mere $5 with free shipping. Just look these S-Specs up on eBay, list by cheapest, and you should find it (not linking it to not create the sense that I might be affiliated, which is not the case). I'm sure you can message them for a specific S-Spec, but all three are confirmed to be 511 by the ARK, so they should all give a good idea of whether the claims are true or not.

I have ordered one of these CPUs today, and will be reporting back once it arrives and I get the opportunity to test it.

[xsecret]

If you have a cpu-z dump (or online validation) for one of these cpu, I can check if it supports NX-Bit.

Doing a search is much more complex but still possible

[Tech&Music]

[xsecret]

I've just checked C0, D0, E1 and G1 stepping on S478 Prescott.

None of them supports XD-Bit :-/

[max1024]

Wow I missed interesting topic Mome weeks ago I tested SL7QB in modern environment. It was very interesting http://valid.x86.fr/y0g57j
I would like to find SL8JX, but so far this has not been possible. The best motherboard for such experiments of cource - ASRock P4i945GC

[i845pe@800+MHZ]

Was just browsing this forum for the first time in months and noticed a mention of the elusive SL8JX. Just so happens I bought one from a UK ebay seller back in 2011 for a whopping $7 at the time. The bad thing is I don't have a platform to do any testing for the XD-Bit or EMT64.

[CPUShack]

Perhaps you could loan it to someone here that could?

[wytiwx]

According my test, C0 and D0 stepping of s478 Prescott have NX, even if you may not see NX option in mobo BIOS setup

[Wasmachineman_NL]

[Carlos S. M.]

I have tried an SL7QB in some LGA 775 boards with the help of an adapter, mainly some ASUS, couldn't find the NX bit option available, but will keep investigating

[Calbris]

[wytiwx]

Actually, you don't need to focus on NX option in BIOS, it's an inner behavior of CPU, BIOS do nothing with this.

You can see my thread about s478 CPU running win10 on a chinese forum:

https://tieba.baidu.com/p/6737041814