I just wanted to post Victors resistance values for anyone following along. It's interesting to see a direct comparison of these. I want to point out that the 2 JSD-001's have different RSX models (CXD5301 on the working console and CXD5300 on the GLOD). It's shouldn't matter? But maybe there are slight differences in the resistances we measure. Also, some of those values will be different on every console. So we're really looking for values that are way off.
Working CECH25xx (JSD-001) and known good RSX (CXD5301)
- VDDC = 2.7Ω (A Healthy value. New ≈ 3.2Ω)
- VDDQ = 100.3Ω
- VDDIO = 96.5Ω
- YC_RC_VDDIO (FlexIO) = ? (He forgot to measure)
- VDDA = 61.0Ω
- VDDR = 449.6Ω
CECH25xx (JSD-001) GLOD Diagnosed with a Dead RSX (CXD5300):
- VDDC = 1.7Ω (Marginal)
- VDDQ = 235Ω (High)
- VDDIO = 95.5Ω (Same)
- YC_RC_VDDIO (FlexIO) = 12.6Ω (Unknown/No comparison)
- VDDA = 56.4Ω (Same)
- VDDR = 315.8Ω (Low)
Discussion:
1.7Ω VDDC is a bit low, but it's within margin. If this was LINK, he'd have one heart left and be panting. But he's not dead yet. There is enough separation on the Core voltage to rule out a short. That's the most common place to burn out.
I would normally be thinking bump failure on the die, if weren't for the GLOD. The RSX must be able to send/receive information to/from the CPU/SYSCON, otherwise it would have triggered a YLOD in POST/BitTraining. So I think that might rule out DIE bump failures.
However, if there were bump failures on the RAM, leading to internal shorts or open lines, then perhaps it's not able to boot because the RSX Die can't communicate properly with it's onboard RAM. Since the issue is on the RSX itself, it's not on the motherboard and doesn't prevent the RSX from responding to SYSCON check-in's, the SYSCON doesn't throw an error code because the RSX is suffering in silence. So the system is stuck in limbo (GLOD) while the RSX fails to get it's $h!T together.
Bump failures seem more likely to me, probably between the DIE and RAM. Perhaps an SMD component on the RSX substrate? Might be worth probing those values with a good chip to see if there's a difference there. If so that would be an easy fix. VDDQ and VDDR are both related to the RAM. And they are the only ones significantly different. These readings rule out short conditions, but not an electromigration open line fault. VDDQ is high, perhaps that's why. It's hard to know what effect an open line fault on some microscopic trace inside the DIE or RAM would have on resistance measured there. Maybe a Bump on the VDDQ line cracked and increased the resistance. That narrative lines up with what we know about aging solder joints - the resistance tends to increase with deformation and oxidation, until an open line forms. However, we also know some resistances, like VDDC tend to decrease. VDDR is the RAM's main voltage, like VDDC is the die's core voltage. Perhaps the lower VDDR is kinda like a health meter for the RAM. Isn't VDDQ used for voltage reference, among other things? It can't be good if it's significantly off.
EDIT:
I just noticed that the difference between the working and GLOD RSX is the same for both VDDR and VDDQ. VDDQ is 135 ohm higher. VDDR is 134 ohms lower. They are both off by about the same amount? That seems sus!
EDIT2:
VDDQ: The supply voltage to the output buffers of a memory chip.
VDDR: Supply voltage to the memory.