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 Post subject: Another WHY Question here... !
PostPosted: February 12th, 2019, 6:06 
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Hello guys,

I was wondering for the last few days about this Question here which is: Why is WD PCB`s repairable (at least some of them) & Samsung is NOT?

both share the same MCU (for some cases)...

anyone worked on those or tried?

:wink: :idea: :idea:

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 Post subject: Re: Another WHY Question here... !
PostPosted: February 12th, 2019, 16:50 
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Because people do know how to remove the diode on the WD when it's shorted but people don't know how to patch the FIPS module on Samsung ROM so when it goes bad the drive doesn't spin and the so called DR guys just replace the PCB and call it a un-repairable PCB problem....

Honestly .... is this a real question ? That Marvell MCU pard doesn't make any sense (well, all the post doesn't make sense)...

Why is it so hard to decrypt a truecrypt volume on a hard drive and why is it so easy to gain access to user files locked with windows password ? After all both are on the same sort of hard drive .... if the files are stored on the same media why some of them are so easy to gain access to and the other so hard ? Same for Marvell MCU .... Get something like a Marvell MCU on a PCB with really bad protection like no fuses and no TVS, nothing .... Get the same Marvell MCU on a PCB with a good protection design like lots of protections for all power supply voltages with TVS and Fuses and NOT that junk WD design .... Guess what ... both have Marvell MCU but some when suffering from overvoltage will survive and the others don't because of the way circuit is design ...

Why some crypto IMPLEMENTATIONS do get cracked like for example WEP and other implementations are more or less solid like WPA ? It's the SAME CRYPTO what changes is the IMPLEMENTATION .....

Also are you sure you can't repair a Samsung PCB ?

Majority of DR guys will have no clue about electronic and the only thing they can do is remove diodes, bridge fuses and swap ROMs .... The few ones (most likely you) will bridge the diode , remove the fuse and toast the ROM lololololol The ones that do know how to fix the PCB are happly fixing other appliences and not doing DR lolololol With some exceptions of coure .... at least with @fzabkar exception ....


Why don't you PM @fzabkar to see if he can help you out with Samsung PCB repair ?

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 Post subject: Re: Another WHY Question here... !
PostPosted: February 12th, 2019, 17:34 
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einstein9 wrote:
Hello guys,

I was wondering for the last few days about this Question here which is: Why is WD PCB`s repairable (at least some of them) & Samsung is NOT?

both share the same MCU (for some cases)...

anyone worked on those or tried?

:wink: :idea: :idea:

Very strange question/observation ...

Can you show us one example where WD and Samsung use the same MCU? I had assumed, perhaps incorrectly, that each MCU was specially designed for each customer.

What do you mean by "repairable"? Clearly your understanding of the word differs from the rest of us.

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 Post subject: Re: Another WHY Question here... !
PostPosted: February 13th, 2019, 3:18 
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Spildit wrote:
Because people do know how to remove the diode on the WD when it's shorted but people don't know how to patch the FIPS module on Samsung ROM so when it goes bad the drive doesn't spin and the so called DR guys just replace the PCB and call it a un-repairable PCB problem....

Honestly .... is this a real question ? That Marvell MCU pard doesn't make any sense (well, all the post doesn't make sense)...

Why is it so hard to decrypt a truecrypt volume on a hard drive and why is it so easy to gain access to user files locked with windows password ? After all both are on the same sort of hard drive .... if the files are stored on the same media why some of them are so easy to gain access to and the other so hard ? Same for Marvell MCU .... Get something like a Marvell MCU on a PCB with really bad protection like no fuses and no TVS, nothing .... Get the same Marvell MCU on a PCB with a good protection design like lots of protections for all power supply voltages with TVS and Fuses and NOT that junk WD design .... Guess what ... both have Marvell MCU but some when suffering from overvoltage will survive and the others don't because of the way circuit is design ...

Why some crypto IMPLEMENTATIONS do get cracked like for example WEP and other implementations are more or less solid like WPA ? It's the SAME CRYPTO what changes is the IMPLEMENTATION .....

Also are you sure you can't repair a Samsung PCB ?

Majority of DR guys will have no clue about electronic and the only thing they can do is remove diodes, bridge fuses and swap ROMs .... The few ones (most likely you) will bridge the diode , remove the fuse and toast the ROM lololololol The ones that do know how to fix the PCB are happly fixing other appliences and not doing DR lolololol With some exceptions of coure .... at least with @fzabkar exception ....


Why don't you PM @fzabkar to see if he can help you out with Samsung PCB repair ?


Did you understand my Question 1st.? if not, then you may ask for clarification instead of jumping to your own conclusions here...

I mean Repair with 3k (do you own one?)... when you write the wrong ROM by mistake the PCB dies, and there is a way to repair it (in WD using 3k)
my Question was why not Samsung PCB!!!

As for your Question to ask "fzabkar" for help, i think i posted before about bulk PCB repair on this forum (not hard to find) but none replied (including your friend)
then i sent to one Chinese friend who did it (and got paid).

@fzabkar

not strange, you may look @ those 88ixxxx MCU`s and will know in both WD/SAM.

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 Post subject: Re: Another WHY Question here... !
PostPosted: February 13th, 2019, 3:32 
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@einstein9, "reprogrammable" is not the same as "repairable". In any case, it is wrong to say that something can't be done just because PC3000 is unable to do it.

As for those "88ixxxx MCU's", I've been looking at them for the past 10 years and have never noticed that WD and "SAM" share any of them. Please, could you enlighten me with a specific example?

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 Post subject: Re: Another WHY Question here... !
PostPosted: February 13th, 2019, 4:11 
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fzabkar wrote:
@einstein9, "reprogrammable" is not the same as "repairable". In any case, it is wrong to say that something can't be done just because PC3000 is unable to do it.

As for those "88ixxxx MCU's", I've been looking at them for the past 10 years and have never noticed that WD and "SAM" share any of them. Please, could you enlighten me with a specific example?


look here @this image, MCU`s are 88ixxxx
WD: 701499 - 88i6745N
Sam: 00249B - 88i8823

In both no ROM chip

Before in this WD pcb there was a way to remove few resisters (can`t remember sure not) and you solder a ROM chip and go on
now in 3k (using terminal no need to solder anything)

hope its clear now.

thank you


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 Post subject: Re: Another WHY Question here... !
PostPosted: February 13th, 2019, 4:34 
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@einstein9, something got lost in the translation. By "same", I took you to mean "same IC", not "same IC manufacturer".

In any case, IIUC, HDD manufacturers would be involved in designing the specification for Marvell's SoCs, presumably by selecting cores and peripherals from Marvell's library of components. In other words, I suspect that MCUs are custom parts, assembled from standard components, as specified by the HDD manufacturer. I doubt that Marvell produces general off-the-shelf products for the HDD industry, at least not in the past 10 years.

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 Post subject: Re: Another WHY Question here... !
PostPosted: February 13th, 2019, 5:11 
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@fzabkar, i have to agree with you here, sometimes i write directly without thinking that others may not understand the point of the question...

Anyway, as i was saying here, about WD for example 3k terminal is able to communicate with the MCU directly through terminal and write ROM back and ur done
if WD is able to do it why samsung is not? (both share the same MCU) thats what am working on now....

some part of the MCU memory (maybe) is reserved for the ROM and if they figured it for WD why not Samsung?

maybe @the end of the day all of this is not worth wasting my time on since Seagate bought Samsung....etc

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 Post subject: Re: Another WHY Question here... !
PostPosted: February 15th, 2019, 10:49 
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WD do use BOOT CODE MODE. If you bork the ROM you can send a pattern by terminal (FFFFF characters) at power up and the MCU will not read ROM either from chip or internal masked ROM space. Instead it will drop to boot code mode and will allow to read/write ROM. This is because there are READ ONLY code on MCU that at start will allow for internal or external ROM to be programmed.

On Samsung if you do damage the ROM code in a way it will no longer properly start you can't re-program it again without external programmer assuming you have external ROM chip.

It would be like flashing a motherboard BIOS. Some motherboards will still boot to a "safe" mode even if you do manage to damage the BIOS code in order for you to re-flash the ROM/BIOS. Some motherboard will even allow you to use a floppy with new BIOS code even if you did damage your old BIOS code by wrong flashing. Other boards will not allow you to do that and if you kill BIOS you have to re-programm with external programmer.

Depends on implementation only.

On Samsung you can kill FIPS section and still be able to read/write ROM.

You should be able to kill the "end" of the ROM and still be able to do some reading/writing depending on the affected code.

The code to read/write ROM on WD is still present on the MCU as a boot code even if the entire ROM space is cleared. On Samsung the instrcuctions are on the ROM code itself so if you kill the ROM code you can't read/write ROM again as there are no known boot code mode or extra code to re-programm rom (as far as i know).

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