Xbox Cpu Upgrade to 1GHZ Attempt

So, here is my newest craziest mod. I hope I can pull it off, but I am not 100% sure that I can. Here is what my plan is. First I am going to take the original Xbox cpu off the board and replace it with a 495-Pin BGA socket. This is it here








Then I will place the new micro-pga2 CPU into the socket. Here are some pictures of the new cpu.








and the CPU fitted into the socket





I could just detach the cpu from the interposer and then attach the cpu straight to the board, but I think it would be nicer to have a socket in between so I can switch out the CPU if I ever have to.


Now the hard part is figuring out 3 modifications that I need to do to the Xbox motherboard below the CPU before attaching the socket. A member of XBMC4XBOX forums by the name of N64 Freak has successfully done this upgrade, and he said "I had to cut 2 traces and set one connection between two pins. The xbox now reads 1000mhz. So summarized i just missed to disable speedstep and get the xbox to read the FSB correct." If I can figure out which modifications he made then I believe I can actually pull this off.


The people who have pulled this upgrade off, seem to be very reluctant (understandably so) to share information so I don't think that they are going to just give me the answers, I need to figure them out. N64 Freak told me that if I want to figure it out, I should read this document from Intel.


http://download.intel.com/design/mobile/datashts/p3_ds.pdf


I have read most of this document, but it is still quite confusing to me. So far I am thinking that these are the three modifications that I need to make to have the Xbox read 1GHZ processing power.





But I am not absolutely positive. Does anybody here know more than I do on this particular subject?

 

I'm actually starting to think that the cutting signal "BLCK" is not right, because of this





The zero's in that chart mean that the pad is populated, and a 1 means the pads is depopulated. (Populated means that there is a solder ball there, and depopulated means that there is no solder ball there) another way to make it depopulated would be to cut the trace leading to that pad. So instead of cutting signal "BLCK" maybe I should be cutting signal "BSEL1" and "BSEL0". That should give me the correct fsb speed of 133mhz.

 

Um. The Xbox operates at 133MHz FSB clock. So if what I'm seeing is correct then you shouldn't need to cut anything for the FSB clock.

 

The mobile p3 1ghz processor operates at 100mhz fsb speed though, not 133. Unfortunately.
This is from the Intel document.

"BSEL[1:0] (I – 3.3V Tolerant)The BSEL[1:0] (Select Processor System Bus Speed) signal is used to configure the processor for
the system bus frequency. Table 36 shows the encoding scheme for BSEL[1:0]. The only
supported system bus frequency for the mobile Pentium III processor is 100 MHz. If another
frequency is used or if the BSEL[1:0] signals are not driven with “01” then the processor is not
guaranteed to function properly."

I guess I could try to set it at 133mhz, but it might cause problems.

 

Ah. OK then. Sounds like you would be better going with a Tualatin using the mobile to socket 370 adapter. Can't pull my Tualatin powered machine apart as Trusty applied generous amounts of epoxy around everything to make it stay put and to no doubt prevent others from seeing how he does it.

 

There is no adapter like that, that you can just buy. Trusty has them custom made. I could design one, but I think that is a little out of my range of ability at this time.

 

If you do not use the socket you can use the stock heatsink. I have a 1GHz thay uses the stock heatsink and it runs fine without overheating problems!

BTW mines runs at the full 133 FSB and it has no socket.

 

Thanks for letting me know that davidthomas. So I guess setting signal BSEL to [1:1] will not mess it up then. Very useful information. I believe you can still use the stock heatsink with a socket installed. I think Trusty mentioned this a long time ago, on the Xbox-scene forums.

 

Mine was done by N64 freak and it is awesome! He would know the answers that you need

To bad the xbox-scene is gone now! There was so much awesome info there!

 

Yeah, I know that he knows the answers, but it doesn't seem like he really wants to share the information, cause I think he feels that he would just be getting robbed of the information that he had to work hard to get himself, with no assistance from others.

 

Cant blame him. I am sure you will get it if you are this close already.

 

I don't know about using the 1GHz CPU on your mod but I do know on my console that Trusty ran a small jumber wire on the bottom of the PCB. My console is a 1.1 like yours. I can take a picture if needed.

 

Yeah sure, thanks sonicdude

 

Really a jumper wire? I have a trusty 1.4GHz version 1.1 also and it does not have any jumper wires on the top or the bottom. Also my 1GHz version 1.1 does not have any jumper wires on the bottom or the top of the board. Only wires on the boards are the X3 modchip wires that goto the D0, HDD activity and LAN activity.

 

I have 3 Trusty 1.4ghz boards, two without the jumper wire (v1.0 & v1.4) and a v1.1 with the jumper wire. Strangely the ones without the jumper wire under the pcb seem to run alot cooler :/.

Good luck with the 1ghz mod, I also have a 495 socket and 1ghz SL53S cpu on hand so very interested in this thread to see if you work it out.

 

Where is the jumper wire at? I wonder what it is for! Now you got me curious! Mine is a version 1.1 also. I am gonna take it apart tonight to be sure.

 

My 1GHz also has no jumper wire version 1.1 board

 

Anyone who has the skills to seriously go about something like this would have few issues in figuring it out short of needing time. I don't remotely blame trusty for keeping his info a secret given it wouldn't be that hard for someone with a BGA reworking setup to go about installing replacement chips.

Putting aside the socket adapter too. Suppose you could salvage socket 370 ZIFs to start with but it'd probably be a lot better to, as mentioned, custom fabricate these things.

Some speculation on the jumper wire: when the Tualatin PIII came out many earlier mobos couldn't support the CPU due to some changes in the pin arrangement. IIRC it was mostly power pins? Doesn't really matter the short version is that you either cut the pins on the CPU and soldered wires to the cut pins (modding the CPU side only) or you cut the mobo and soldered wires there (mobo side only mods). I wouldn't be remotely surprised if this wasn't the same thing going on and if for some installs the wire wasn't necessary (the socket was built with the Tualatin in mind) and for others the socket was modded for use with the Tualatin. This assumes that these sockets were produced before anyone ever thought about installing a faster CPU into the XBox or at the very least before anyone decided to try installing something faster than what would natively fit.

 

OK. My picture taking sucks. Bad camera. So instead have a high resolution image of a bare 1.1 board I found. Look closely at the middle left side to see the jumper. I marked it with a red line between the points that are connected on my board. No traces seem to have corrosion or been cut.

 

It's not like I am a total newb at doing Xbox modifications. I have done everything you can think of except for this. That is why I wanted to try. Thanks to the people that were trying to help though.