How important is to look for matching DCM?

[Scorpion]

Hi all,

I heared few differenr opinions about matching the last 4 letters of the DCM between the patient drive and the donor drive while looking for donor drives.
Some say that the DCM is not important and some say that donor matching is based besides model and date also on DCM.

Personally I run through cases that I ordered donors drives which were have the same DCM 4 last letters as the patient but those drives weren't compatible with the patient.
Recently I ordered 2.5 250GB WD drive with the exact 4 DCM letters as the patient but found out that that it has 3 heads while the patient has 4 :/

Best Regards,

[Doomer]

DCM cannot tell you number of heads

[LoboX]

DCM cannot tell you number of heads

I was searching the forum for that info couldn't actually found something that i can use, is there a way to know how many heads the hdd has?

Thanks

[ShaneWard]

I would have thought one would go with how big the hard drive is, find one with the matching capacity from the same year.

Shane

[LoboX]

I would have thought one would go with how big the hard drive is, find one with the matching capacity from the same year.

Shane

Thanks Shane so check for the LBA then, so you can get the correct amount of heads, if you cant get a drive close to the date i guess something at least close will do the job.

[irs]

I would have thought one would go with how big the hard drive is, find one with the matching capacity from the same year.

what about areal density? you can have different number of heads for same drive's size.

Bye
Luca

[hddguy]

I would have thought one would go with how big the hard drive is, find one with the matching capacity from the same year.

what about areal density? you can have different number of heads for same drive's size.

Bye
Luca

Also, same head count but different head map. This is common

[LoboX]

I would have thought one would go with how big the hard drive is, find one with the matching capacity from the same year.

what about areal density? you can have different number of heads for same drive's size.

Bye
Luca

Also, same head count but different head map. This is common

when you think you know something, something new pops up i didn't knew about the areal density, and i never tough the heap map will be needed to do a head replacement. but quick question cant you just edit the head maps? to make the heads work on the drive.

[Doomer]

when you think you know something, something new pops up i didn't knew about the areal density, and i never tough the heap map will be needed to do a head replacement. but quick question cant you just edit the head maps? to make the heads work on the drive.

if you need H1 and your donor's HSA missing H1 physically, then no matter how you edit the map, you will never be able to read surface 1, unless you move the platter to another physical position (which is not a good thing to do anyway)

[LoboX]

when you think you know something, something new pops up i didn't knew about the areal density, and i never tough the heap map will be needed to do a head replacement. but quick question cant you just edit the head maps? to make the heads work on the drive.

if you need H1 and your donor's HSA missing H1 physically, then no matter how you edit the map, you will never be able to read surface 1, unless you move the platter to another physical position (which is not a good thing to do anyway)

Oh OK thanks, but lets say you have the exact drive and heads on your donor, i know the head map is different cause each head can read from a different platter, cant i edit the head map there, in that situation?

[Doomer]

I don't understand your question

[LoboX]

Sorry OK lets say you have a donor drive with matching heads, everything looks the same but the head map is different on each drive, if you replace the bad heads with the new donor heads cant i edit the head map on the drive i am working, so i can make the head work?

[Doomer]

Yes you can, but you can only read heads that have the same number on both drives

[LoboX]

Got it, thank you Doomer

[Scorpion]

Hi,

We are a little bit out of the subject..
Do you look for matching 4 DCM letters on the patient drive and donor or not?

[jono-ats]

Sometimes I look for 2, but usually not.

[Scorpion]

Sometimes I look for 2, but usually not.

What do you look for inorder to find good WD donor drive?

[jono-ats]

It depends upon the model and family, and what you are trying to do (e.g. swap heads, PCBs, make a hot swap donor, etc.). With some drives (esp. earlier ones) DCM is important, but less so with the newer Royal family (seems like I've broken every DCM "rule" with the latter).

There is a lot of conflicting info on the 'net about DCM and much of it is wrong, or else it is "right" some of the time but not always.

[Matiw]

Does not the areal density dependen on the technology available at the time of manufacturing ? Does not close manufacturing days mean similar areal density ?

what about areal density? you can have different number of heads for same drive's size.

Bye
Luca

[jono-ats]

Areal density is not related to DCM. it's a separate topic.