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LPC diagnostics (v0.1) Tutorial written by : milingo Last edited: August 5, 2004 Note: Tutorial is for Xbox v1.0 to v1.5. LPC has most points unlinked on Xbox v1.6+ LPC diagnostics, i.e. how to use a multimeter to check a funky LPC or broken traces without losing your faith. My dear (de)solderers, in my search for mod-knowledge (and misadventures with FRAGging 'boxes) I found a lot of misinformation, or better partially incorrect infos, regarding the dreaded LPC. I started organizing these infos for myself but, as the whole scene is about sharing knowledge, I decided to trim the rough edges and write a document out of it. I found it necessary because well known forums disregard 3-letter word searches (like PIN and LPC) and when you're at your first attempt with soldering and end up for the 3rd time with a FRAGging 'box you tend to forget words like PINS, LCLK, LAD0,1,2,3 and LFRAME! My work is 90% forum reading and 30% trial and error, (yes i know it's 120%, but even in nice forums like the one we have, a good 20% of infos you find are bill$h*t). One more thing, you'll find stolen photos and diagrams in this doc. I tried to use watermarked ones so I hope it's clear it's not my work, anyway if anyone feels ripped offended or generally pissed off by it, well... write me and I'll redo the images from scrap. Just one more thing, as many of you have already understood, English is not my mother tongue, so before flaming me please try to understand the concepts underneath! (if you find a sentence particularly awful, write me and I'll try to rephrase it, but things are really quite simple.) How to use a multimeter for voltage and resistance (ohms) testing: A. Voltage testing (cheching cold joints...) 1 You need to select on the voltmeter (or multimeter) the V scale DC current, set it to 10/20 (not lower than 10!) cause maximum voltage to measure is 5,0 volts, and we don't want to fry it (modern voltmeters are protected but you'll never know what kind of grandpa's voltmeter someone can come out with...) 2 You need to switch the 'box ON, remember that you have to access the LPC on the mb so hd and dvd must be peeped out of the case or removed completely (but take note that it will FRAG anyhow if you don't keep the discs connected and powered). 3 Put one tip (black one usually) on a ground like the screw near the LPC (or pin 2 of the LPC, but it's easier a farther point). 4 Push firmly but softly and with a steady hand the red stick in the hole you want to test, or keep it pressed against the pin you want to check (just remember not to touch more than 1 pin at a time otherwise you'll never know which one are you reading... ) 5 Read on the voltmeter your current. This is my friend the LPC A good working LPC, and a nicely installed pin header, should roughly read, for me it's always a bit lower (as far s is 10% near the number it's ok): picture by ozxmods.com Pin Name Voltage 1 LCLK 0.2V * 2 GROUND 0.0V 3 LFRAME 3.3V ** 4 doesn't exist! 5 LRst 3.3V 6 VCC5 5.0V 7 Lad3 3.3V 8 Lad2 3.3V 9 VCC3 3.3V 10 Lad1 3.3V 11 Lad0 3.3V 12 GROUND 0.0V * not 3V, if you want a precise reading switch the scale to 1-2 V) ** on V 1.3+ 'boxes (0.0V it's disconnected) Common misinformation I found in the forums "...all pins should read 3.3V except pin 2 (0.0V) and pin 6 (5.0V)..." as you see pin 1 and pin 12 do not read 3.3V... B. Resistance testing (checking trace continuity...) 1 Select the ohm scale on your Multimeter (or Omega greek letter, the one like a reversed U, like the watch brand if it still exists) 2 Keep your 'box OFF, there's no need to risk to fry it... 3 Put one point (it's the same which one) in the pinhole and the other in a corresponding check point (see image white lpc point goes with grey eye-point, like the d0, on the mb) 4 In a circuit like this with little resistance, if trace is ok the ohm-meter should read nearly 0, if it's broken or messed up it shall read a high number say 1 This is a useful photo that pinpoints back of the mb with the lpc pins and corresponding check points. picture by baldbouncer.co.uk Somebody wrote in a forum this image has one grey check point wrong. Please help me find the culprit (if any)! Really this image has the points differently/oddly numbered but I'm too lazy to redo it right now so I enclose this translation table Rightfully numbered LPC pin Baldbouncer's Image numbering 1 1 2 11 3 2 5 3 6 10 7 4 8 9 9 5 10 8 11 6 12 7 Just be sure to double check before you start swearing!! Well that's it. My friend I hope it's been useful. Cheers! Your friend Milingo If you need to contact me try thru xbox-scene forum.... Version 0.1 (any corrections are welcome!) Tutorial written by : milingo
As we know, v1.2-1.4 Xboxes don't have an easily-accessible LFRAME# signal, so modchips work on the assumption that the southbridge will never abort a cycle early by asserting LFRAME# and driving 0b1111 onto LAD[3:0]. That may be true for memory read cycles, but what about memory writes and I/O read/write cycles? Besides a timeout (which shouldn't happen anyway if long wait states are used), is there ever a case where the MCPX might abort an LPC cycle? EDIT: I may have posted this in the wrong section. I need this info for a hardware mod, but it might be better suited in the Modchip or General forum. Sorry about that.
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