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Cpu Work, Spitballing.

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Following the footsteps of these gentlemen & crew:
N64 Freak
I intend  to upgrade the CPU in my Xbox, for Linux performance.
At some point (after I have an SMD rework station) I intend to upgrade the RAM also.
At this stage I'm just researching the feasibility, and seeing what I'm jumping into.

I believe I can use a CPU socket (495) from a mobile Pentium 3 to use a P3 1 GHz "SL53s" with minor accommodations made.
I will need to comb over the datasheets as I don't currently know If I can just "drop in" a faster 495 mobile celeron/P3, say after I've installed a CPU socket from an old laptop.

Processors I've seen photos of installed in adapters include:
SL5XL The Tualatin 1.4 GHz 512KB L2 Cache and 133MHz FSB 
SL53S Seen in N64 Freak's 1GHz mod, apparently using a cpu w/ 100MHz FSB is not out of the question.
SL657 Seen in an adapter board somewhere.
I wouldn't try an SL6BY because the core voltage is lower than 1.5V and the original CPU used up to 1.7V

Some concerns I have:
VID Voltage Range, VID[4:0]
SSE Technology,  SpeedStep Technology.
GTL+  (do any of the cpus use the older GTL, if not then it is not a concern at the moment)
Bus Speed: Can I use a chip with 100 MHz FSB? Nobody wants to downgrade..
L2 Cache:  Does this matter? Can I simply use a chip with more, believe I can because Trusty & N64 freak have already done this without issue.

To slow the CPU speed, they are apparently using STPCLK# assertion. This is accomplished on the adapter PCB with the necessary support components added.
My first attempts will not include provisions to slow the performance, as playing games on the console will not be an immediate priority.

I'll have to check the usual places and see if I can locate a CPU area schematic for the Xbox, I believe it is in the wild, if anyone has details, please PM me!
The socket 370 to 495 adaptor shouldn't be too difficult to create seeing as how I have some datasheets to work from.
First attempt I will use a standard 495 PGA mobile cpu (currently looking for one w/133 FSB) in a recovered 495 socket, then comes the task of designing an adapter board to go from 495 to 370.

If N64 Freak would like to comment his words will be greatly appreciated, I'm not here to steal anyones thunder; just looking for a performance gain.
I have datasheets from that era attached below, I'll have to see if the SL5sn (xbox) CPU is mentioned.
Thanks everybody!

---All The Best---






III Processor 1400 512KB L2.pdf



Edited by LeapFrogging
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Thank you neighbor,
I may just have to humbly ask the man through a P.M.  I don't want the entire information, no spoon feeding; but a few tips in the right direction would be awesome!


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After searching the net I've found some more clues out in the æther:D

I found a post by..  N64 freak! on another forum.


but i missed some modification that you can't see.
just a hint, they are hidden under the CPU!
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.

So Speedstep must be disabled I assume , and if you are using a CPU with 100 MHz front side bus, then the xbox must be made to read the FSB correctly?
If I used a CPU with 133 MHz F.S.B. I should be good to go? :/

 I will need to study the data sheet and see how to disable Speedstep, that would be half of what I need to know to use a 1 GHz CPU @ 1 GHz and not  933 MHz. :)

Edited by LeapFrogging

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you dont need a rework station for the ram, just the CPU (I think, I;ve never done that upgrade)  all you need is a steady hand and a fine tipped soldering iron. 

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The slotted ones will not work, at least I don't think the physical chip has the same layout (I could be wrong though because I haven't had the chance to examine one 1st hand).

The mobile CPU from a laptop is nearly a drop in replacement.

Sorry I never made any progress on this, I was away for 6 months last year and dropped this project in the process.

I'd like to revisit this, if I ever get the time to get to it,

Edited by LeapFrogging
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1 hour ago, transitman55 said:

Is it possible to use desktop P3 CPU's? If so, I still have a bunch of them!

p3 cpus require an interposer board to handle the pin remapping.

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Board startup date: April 23, 2017 12:45:48
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