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Next attempt at a board that can hit 340 MHz --> It works! - Page 11 — Parallax Forums

Next attempt at a board that can hit 340 MHz --> It works!

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Comments

  • RaymanRayman Posts: 14,148

    About to attempt chip swap...

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  • evanhevanh Posts: 15,405

    Why? Seems to me like you're throwing away a good Eval board.

  • RaymanRayman Posts: 14,148
    edited 2023-11-10 01:54

    Maybe not if chips are same…
    Fun experiment anyway

  • It could be a useful test if neither chips are damaged in the process. It will at least tell you if one chip performs better on a lower performing board than another...assuming soldering doesn't significantly affect results. Hopefully the soldering is good. Will be interesting to see what happens. Also in particular to see what happens on the EVAL.

    You even also put things back later as it was, and see if good performance returns to the EVAL - if not that might indicate that the soldering process is likely to affects things.

  • evanhevanh Posts: 15,405

    Don't you have a number of Prop2 ICs you've been testing with already? Seems to me that pulling one from an Eval board isn't achieving anything.

  • jmgjmg Posts: 15,155

    @evanh said:
    Don't you have a number of Prop2 ICs you've been testing with already? Seems to me that pulling one from an Eval board isn't achieving anything.

    I think the idea is to take a known-measured-exact-MHz part from EVAL and see how many MHz the same part decreases by, on the second board.
    (and how many MHz the other P2 increases by, on Eval)

  • evanhevanh Posts: 15,405
    edited 2023-11-10 10:16

    Looking for ghosts doing that. And that's assuming nothing goes wrong.

    Really need a way to rapidly measure the die temperature. If Chip does a respin at any stage then I'll be asking for an internal diode voltage measurement to be added next to the reset/brownout circuits.
    EDIT: The diode would be even better located in the middle of the "eggbeater" crosspoint switch, but I doubt he'd have that as an option.

  • RaymanRayman Posts: 14,148

    Transplant complete.
    A2 board with Eval's chip is now one of my best. Not the best, interestingly, but very close.

    Eval board with A2's chip is dead :(

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  • jmgjmg Posts: 15,155

    On the next rev, you could allow two holes, and connector, to mount a cooler ?
    I see this Fan+Plate is just $5, for Pi 5
    https://www.adafruit.com/product/5815

  • RaymanRayman Posts: 14,148

    Good idea... The 30mm X 30mm fans seem popular:
    https://www.amazon.com/dp/B076H3TKBP/

  • roglohrogloh Posts: 5,283
    edited 2023-11-11 00:41

    @Rayman said:
    Transplant complete.
    A2 board with Eval's chip is now one of my best. Not the best, interestingly, but very close.

    Eval board with A2's chip is dead :(

    This is an interesting result. Pity your original A2 chip is dead (maybe resolder will revive it). Looks like your performance limits are either thermal related to soldering or just the P2 chip variation, and not the other A2 board components or board itself (unless the nearby resoldering improved these support components somehow).

  • RaymanRayman Posts: 14,148
    edited 2023-11-11 00:44

    If we assume the soldering doesn't impact results...

    Seems Eval board is definitely better with same chip. Not surprising given 2 oz copper (?) and 6 layers.
    But, only ~ 10% faster, maybe not worth it?

    Seems to point to my board to board speed limits being chip dependent.

  • evanhevanh Posts: 15,405
    edited 2023-11-11 01:00

    But you do know resoldering makes a difference. I don't think anything was learned.

  • We learned that other components such as regulator and crystal stuff is not necessarily the main contributor to the problem of some of Rayman's boards performing worse than others. It's mainly chip variation or soldering related. Could well be due to soldering if most of the P2-Edges and EVALs seen to date have little performance variation. I think this was useful.

  • evanhevanh Posts: 15,405
    edited 2023-11-11 02:31

    The variations are small when the soldering is good. The variations are large when the soldering is bad.

    EDIT: To put that another way: When testing for small variations, the soldering quality can always be blamed.

  • RaymanRayman Posts: 14,148

    I chased soldering for a while but am now convinced that is not an issue.

    Plus the fast failure mechanism is too fast for soldering to matter. Pretty sure is internal to chip.

  • evanhevanh Posts: 15,405
    edited 2023-11-11 12:31

    Grr! Of course the soldering is not the issue ... but it is what you're seeing because you're looking too hard for small variations ... and you can't eliminate it. It's like noise in the signal. You're seeing ghosts ... or UFOs if you like. ;)

  • RaymanRayman Posts: 14,148

    It is something like that…
    Wish there were more examples (or any) here to look at in 4 layers…

  • RaymanRayman Posts: 14,148

    Here's the final results of first group.
    Also, posted the design files to top post.

    There is definite correlation between simple VGA overclocking test and NeoYume test.
    Solder paste thickness and type less clear, likely doesn't matter...

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  • hinvhinv Posts: 1,253
    edited 2023-11-13 19:04

    @jmg said:

    @evanh said:
    Don't you have a number of Prop2 ICs you've been testing with already? Seems to me that pulling one from an Eval board isn't achieving anything.

    I think the idea is to take a known-measured-exact-MHz part from EVAL and see how many MHz the same part decreases by, on the second board.
    (and how many MHz the other P2 increases by, on Eval)

    Do chips permanently degrade at all with soldering and desoldering?

  • evanhevanh Posts: 15,405
    edited 2023-11-13 21:47

    Performance won't degrade, no. But material stress will eventually fracture joints in a sudden failure.

    EDIT: Err, maybe the thermal pad bonding to the die can be gradually degraded and thereby degrade thermal conductivity. Dunno.

  • jlsiliconjlsilicon Posts: 92
    edited 2023-11-18 23:43

    Interesting board.

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