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[alikaz]

QUOTE

One thing to keep in mind here is that when the xbox does a quick reboot, it reinitializes the data segment out of the uncompressed copy in the bios. If there are any differences in the data segments between the two bioses, then you have the potential to run into problems. During a quick reboot, it zeros all but 4KB of the system heap and the kernel bss segment. It then overwrites the data segment with the uncompressed copy in the bios. This effectively resets the kernel back to the way it was after the initial load. The biggest change with bios swapping like this is if you have different kernel versions in the system flash and in the modchip. There are quite a few differences in the data segment between the 3944 and 4034 bioses.

wut talkin

[alikaz]

Captain_Dunsel, i seriously dunt get ur on/off schematic for a home brew, like when the chip is "on " pins 16 and 32 are conneted to each other rite? dusent that mean u jus conected the power and hte ground to each other...???o.0, and when the chip is off it shows that the 32 is conected to "#E" which makes some sence, but i still dun get how it "works" ....pls explain

[mark986]

This just got all crazy. I'm just waiting to get my disable switch put in, but I buy all the games I want to play online.

[Captain_Dunsel]

OK, so I'm gonna try to address multiple questions/comments in one posting.

david123, your approach to supporting multiple drives (cable all of them to the IDE, and switch power to the ONE drive you want enabled at a time) should work just fine.  This is the technique used by Ferrell in his Project 411GB tutorial, found on this site.  As for the merits of switching EEPROMs and techniques for doing so, I'll leave that to others.

alikaz, these next two are for you...

(dusts off Electronics 101 text book -- it's been a looooong time...)

Referring to Dysfunction's wiring schematic, it looks correct to me.  The key is that pin 32 (Vcc) is never connected directly to pin 16 (ground)... it is connected through a 10K resistor; this prevents the short circuit.  The theory is simple: the Chip Enable pin for the EEPROM (pin 22) is an "active low" signal (thus the bar over the signal name == logical "NOT"); this means that the chip is enabled when the signal present is at logic 0 (i.e. ground).  When the switch is thrown to the right in the diagram (as depicted), CE is pulled
to ground through the 10K resistor; since it is grounded, and it is an active low signal,  the chip is ENABLED when the switch is in the position shown.  When the switch is thrown the other way, CE is tied to Vcc (logic 1), thus the chip is DISABLED.  Again, no short circuit occurs because of the 10K resistor between Vcc and ground.

Actually, going through this exercise with you WAS valuable, as the table in my doc is INCORRECT as written.  You really want to wire one side of the switch to pin 22 on the EEPROM, NOT pin 16 (or else you DO get a short circuit, as the 10K resistor would be bypassed).  THANK YOU FOR HELPING TO CORRECT THIS!  I will update the document immediately.

With your two SPST switches in hand, if you connect one switch to 22 and 32, and the other switch to 32 and E#, you should be all set to enable/disable by turning one switch on and the other off.  Yes, I know you have those switches on hand, but if it were me I'd take the time to go grab an SPDT or DPDT switch and switch both connections as per my tutorial, as I wouldn't want to be bothered with throwing two switches instead of one.  (Yes, I *am* that much of a slacker.)

Also note that Dysfunction's diagram DOES include a 10 uF tantalum capacitor between pins 16 and 32 (ground and Vcc).  This should help with noise problems that could cause instability.  If you do install this cap (recommended), be sure to observe the polarity: one lead on the cap will have a "+" sign, and that lead should go to pin 32 (Vcc).  This is indicated on the diagram.

Based on feedback, I believe I will include the diagrams in the next rev of the tutorial.  In fact, I may very well include much of this text.


Captain Dunsel

[alikaz]

 

[Captain_Dunsel]

(This is pretty hard to explain without knowing how you have things wired, but I'll give it a try...)

Based on your previous comments, I'm guessing that your current installation does not use any resistors or capacitors, in which case you probably have a wire connecting pin 22 to pin 16 and another wire connecting pin 24 to pin 16; thus, the chip is always enabled.  (If this assumption is NOT correct, you'll have to show me the wiring diagram you used for reference.)

If that IS correct, you COULD wire a disable switch by basically just breaking those two wires and using a single SPST switch:
         - Break the two wire connections
         - Wire pin 16 to one leg of the switch
         - Wire both pins 22 and 24 to the other leg of the switch
         - Turn the switch ON to ENABLE the mod, and OFF to break the connections and DISABLE the mod

While this approach is simple, it may NOT work, or may not work RELIABLY.  The problem is that, when the switch is in the OFF position, the Chip Enable signal is not tied to ground or to Vcc; it is just floating in an unknown state.  A floating CE signal might or might not actually disable or enable the chip.   At best, you will get unrealiable selection; at worst, it may not disable at all.

I would strongly urge you to consider following Dysfunction's schematic instead.  It'll mean a little more work for you, but the resistor will keep CE from floating (to ensure stability) and the capacitor will help to smooth out signal transitions (to eliminate other stability problems).  Buying a resistor and a capacitor from Radio Shack is pretty painless; even if you caved in and bought an SPDT or DPDT switch, the whole mess is gonna be around US$5.00.

You can certainly try the method I described above and if it works, hey good for you -- it'll be fast, easy, and cheap.  But let's just say that if I were doing the mod myself, I'd spend the $5.00, take a little extra time, and do the job right.  It'll potentially save you tons of frustration in the long run.


Captain Dunsel

[alikaz]

i duno man, how risky exaclty is it? like is it risky when the mod is off or on? (ex u think the mod is off but actually its on, or u think the mod is on but its actually off.) and pls rember that im using a momentary switch, pls reply bac (and if there is like a SIMPLE resistor i can can some where pls tell me that too(first help wit that then wit the resistor, thx alot too bro)

[Captain_Dunsel]

  And, no, I'm not interested in doing the installation for you.     Don't take this the wrong way, but if this is all still too confusing, perhaps it might be best if you found someone a bit more knowledgeable about electronics to give you a hand.  Buy them some beer, and see what happens -- it always works for me.  

The next post I expect to see from you is one in which you recount your glorious success with this project and shower me with epic songs of praise.  


Captain Dunsel

[Omikron]

QUOTE (david123 @ Dec 11 2002, 08:50 PM)

I'm trying to find out how difficult it is to implement a second HD and a second EEPROM and control them with a single on/off switch. What I want to do is: When the switch is on, my modchip is enabled, second HD is powered and 2nd EEPROM is powered. When switch is off, mod disabled, org HD enabled, also org EEPROM enabled with a 4x IDE cable I connect dvd, hd org, 2nd hd(and one in the mb) If I ever by accident press the 'go live' when mod enabled,only my 2nd hd is screwed and my second eeprom is screwed so I guess I still can get online with the org HD and org EEPROM  and restore my 2nd hd and 2nd eeprom (IF something happens to them). Removing the EEPROM from the mb and connecting a second one doesn't seem to be that hard to do(only 8 connections, compared to the soldering points of a modchip they really are huge) I didn't gain any info about the eeprom yet, so it's still an unknown part for me At the moment I don't know how many connections has to be 'switched'(one for the HD power(maybe both?), one for the modchip and ?? for the eeprom) but I guess 4, 5 or 6 will do. I also don't know if a swith with so many connections does exist. Still a few things to find out, Nothing proven yet, it's just a thought. Comments welcome Also to prevent me of buying a 2nd xbox (Although it will cost about the same)

                                    Note that if you would have actually read the forums you would have seen that I completed this task THREE WEEKS AGO.

http://forums.xbox-s...ST&f=21&t=14123

All I can tell you is that it does indeed work and it was a complete success for me.  The only thing that would make it complete would be a way to hard code the HD Unlock key into the hacked bios, thereby reducing the need for a second drive.

[david123]

Omikron: I check resources before I post a question to prevent asking a question that is already been asked and answered about the n-th time, must have slipped. Sorry about that.


Nice to here it works.

[alikaz]

ok now i have all the things u said uptill the switch done, im gonna do the switch in a bit, rite now im takin a break...man i wus sooo nervous....

[alikaz]

NOOOO, i installed the switch but NOTHINGGGGG it says xbox requires service, my chip is NOT in the socket so THAT mite be problem(its gone for reflashing), but shouldent it load the normal bios if i got it switched off?(but i think thast not workin cuz i got the evox dashbord,) but i tried booting with halo in the dvd drive(orignal) but no luc, im gonna wait for my chip to come bac and then see wut i can doo....damnnnn

[alikaz]

umm aight one more thing that i gotta admit:
im cheap,
so i had bought 2 switches which have 2 pins (simple stuff) frm before
so wut i did (since the 32 is the common one) i put one extension of 32 on one pin of each chip and put the 22,24 one one chip and #E onthe oter one, so when i wanna trun on my modchip i boot with one switch on,and when i wanna boot to orignal,...in theory this should work rite? (pls say yes) well tell me other wise if this shouldent work

[alikaz]

ok so i went out and got a new switch, i got 3 labels on the switch, on, off, and(on), ne ideas where the pins go to??? aight mes out

[Captain_Dunsel]

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Captain Dunsel