[COOLRUNNER] RevA RGH2 on phats tutorial

eldon

Noob Account
Dec 17, 2014
7
0
Hi,
i wanted to share my experience with some RGH2 x360s installs, Jaspers and other phats (7 consoles total).

You may be interested in trying my "unusual" CPU Reset wire path but more importantly considering the amount of tinkering required to get those old CR modchips working with RGH2, i think the most valuable information is the methodology used to make a good install.

Sorry for the rather lengthy text but most of the details require some explaining.
I will also add that i have a fairly extensive background in electronic circuit design but i will spare you the theoretical speculations. And no, i don't know the exact details of the RGH although i have read what was published a while back, recognizing some patterns i experienced on various hardware platforms i worked on.

Hardware used :
Nand-x programmer (not discussed here)
Coolrunner Rev.A (should be the same with rev B and more or less with rev C)
Coolrunner package provided Wires (solid core)

- 1. Initial CR wiring :
get the motherboard out of the bottom case, initial tests should be done on the "naked" motherboard.
Place the coolrunner in its proper final position (on top of the video port), wire the CR pins properly.
Put a 10omh resistor on the CPU RESET Line (CR side, blue wire D) as specified by Xecuter RGH2 tutorial (Rev A B only).

The official tutorial is here (the picture shows the bottom side D point, unused) :
http://team-xecuter.com/xecuter-rgh2-0-official-release/

Do not bother wiring the CPU Reset line with a specific path. Try a short "floating" wire from the CR to the topside D point.
By floating i mean, let the wire float in the air, possibly as far (high up) from the motherboard as your short wire allows.

[you can skip this] Failed shielded wires attempts :
seeing that Xecuter provides a low loss solid core double shielded wire for the CPU reset line, i tested myself some shielded wires i had at hand (ethernet coax, TV, audio), and none of them improved anything, they actually made RGH2 worse, CR not being able to boot my 2 test consoles. Shield was grounded properly.

My guess as to why it failed, would be that my cables were all multicore (flexible) cables, not solid core. Not matter the wire gauge, multicore seems to be the problem.

My last attempt was to actually shield the bare stock CR blue wire as shown on the picture below.
The shielding is aluminum tape i use in bga rework, it is real aluminum.
Against my expectations, it also rendered the wire useless. It was done with the exact same wire that was showing good results, i can only imagine that the shielding turned out to behave like some antenna, adding noise to the wire. Part of the shielding was grounded but since the sticky side is somewhat insulated most of it was not.

diy_shielding_fail.jpg
if you're looking at this picture without having read the text above, i would like to point out that it was a failure.


- 2. Choosing CR Timing :
Once your initial wiring is done and your nand is flashed (ecc or full), with the CPU Reset wire floating, test ALL the RGH2 Timings A B C D falcon Trinity.
10 boots each should be enough to get a good idea of which is "best".

According to my tests i would try them in the following order :
B, A, falcon (B gave me by far the best results on Jaspers and others)
then C, D, Trinity, which never gave me good results on my phats.
D being the worst, putting the console in some rogue state (full fan speed, CR not doing anything), i would avoid it.

By "best" i would consider at least 80-90% of boot within 10 cycles (70% in 5-10 cycles).
That's the average boot time i got on all 7 phats i did in a row.

If you can't get any of the CR timings to boot within those times, try changing your wiring and especially your CPU Reset cable, replace the cable or use a slightly different length although i don't think it is relevant here.

Once you're satisfied with your choice, stick with it !
You will find during the remaining steps that you'll doubt your initial choice and want to test other timings again, spare yourself the trouble, i did that on two consoles and it proved a total waste of time.

My understanding is that, the "short" floating D wire on a naked motherboard, is the optimal setup to get RGH/2 working. Putting the x360 back together will make RGH2 performance somewhat worse.


- 3. CPU Reset wire (D, blue) path & x360 reassembly :
many variations of that wire path have been discussed, some a lot longer than others, the current Xecuter recommendation being to use the short shielded cable straight across the "avoid this area" area, top side.

I personally simply wanted to keep my "floating path" RGH2 good performance while putting the x360 case back together.
I first tried to really let that wire in the air as it was on the bench, but as soon as i would put the motherboard back in the bottom metal case, RGH became poor and even worse with the DVD and the top case.

A quick word about that, the case acts as a shield to prevent noise / interferences from getting out. When you first test the RGH on the naked motherboard, any "noise" emitted is free to fly away, when you put the motherboard back in its "cage", that noise bounces off the metal shields and stays inside, your wire then receives a lot more of that noise.
The grounded shielded wire (i'm not using here) is supposed to handle that problem.

My way of handling that was to actually put the best part of the wire "outside the cage", by making it run top side of the fan "roof" as shown on the pictures below.

cpurst_path.jpgcpurst_path_blower.jpg

My final setup has some tape on the whole cable running on top of the fan roof.
I also added some tape on the metal case borders (under the wire) where the wire bends going down to offer some insulation and/or some kind of strength relief..


You should quickly test (one or two boot) your final wiring while putting the case back together :
1:motherboard in the bottom case, 2:with the plugged in dvd, 3:with the top case, 4:with hdd.

On last thing i noticed is that putting the DVD power cables to close to the CR would degrade RGH, i made sure they where well sticked bellow the DVD, leaving the area around the CR (video port) not too crowded.




- 4. CPU Reset "cleaner" (too little, too late) :
that has also been discussed a lot, it is included on newer modchips and Xecuter has made specific board with some various resistors / capacitors values that you can activate with switches..

Well my electronics knowledge tells me that implementing some sort of passive filtering is essential to get a cleaner signal. But it could also seriously degrade it or make it more difficult to "read" from the CR point of view.
I did test various filtering/decoupling setups, and managed to significantly "improve" (understand "slighty transform") the waveform shape but again it proved counter productive making RGH2 performance worse or more unstable.

My main concern is that blindly trying out some various filtering setups is not efficient, unless you can actually capture the signal on a digital scope.

I added the 10ohms resistor on the D line as specified in Xecuter guide, can't do any arm but won't do much good either. Don't forget you're potentially disrupting the motherboard operation by adding those wires, well the CR actually massively interferes with the circuit in order to produce the RGH, once it's done i expect it goes passive but your wires are still feeding some noise into the circuit.


- 5. RGH2 boot stats :
those stats span across the 7 phat boxes i glitched, all the same way with my Cpu Reset wire path, and with well over 200 RGH2 boot.

I got the following results :
2% instant boot (because it happened more than once)
20% < 5 cycles
60% 5-10 cycles
18% 10-20 cycles
1% well above tolerable (within 5 minutes)

yeah 101% is about right, we're talking hardware bugs right ? my calculator must have some too.

None of the xboxes wandered far from those stats, i would say that one worked not as well as the others (too few <5 cycles boot), but i didn't bother taking a closer look at it.

The main thing i was satisfied with, was the fact the boxes actually booted every time, none would "hang" forever unless i used the D CR timing.

I couldn't really improve the accuracy of the boot time, it would always vary between 1 cycle to 20 cycles. It would have been better to get a consistent X cycles even if it meant having to wait every time.

hope it helped some of you and bored the others to death.

.eldon
 
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