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Myarc HFDC MFM formatting


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#1 BeeryMiller OFFLINE  

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Posted Sun Sep 9, 2018 5:38 AM

I've got a question and I wanted to keep it separate from the DREM discussion.

 

In MDM5 while formatting for a real MFM hard drive, there is an entry for heads.  I have always used what is labeled on the drive.  If it says it has 5 heads, I enter 5.

 

In reality though, does MDM5 and I guess the rest of the world treat it as a total of 6 heads, but starting at as head 0, head 1, head 2, head 3, head 4, and head 5?

 

Beery

 



#2 Schmitzi OFFLINE  

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Posted Wed Sep 26, 2018 10:56 AM

*burp* aah *bump* :)



#3 mizapf OFFLINE  

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Posted Wed Sep 26, 2018 3:11 PM

I don't think there is an odd number of heads. Maybe 5 means "max head number", starting from 0.



#4 RickyDean OFFLINE  

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Posted Thu Sep 27, 2018 3:39 AM

I don't think there is an odd number of heads. Maybe 5 means "max head number", starting from 0.

Here some information:   http://www.pcguide.c...opNumber-c.html

 

http://www.pcguide.c...iaNumber-c.html



#5 InsaneMultitasker OFFLINE  

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Posted Thu Sep 27, 2018 9:41 AM

I think the only place you would see "head 0" is within the low level programming for the controller, where the head number would be specified starting with 0.   A drive with 0 heads would not provide much usable storage. ;)

 

I've never seen a drive with an odd number of read/write heads but that doesn't mean manufacturers didn't make them.  The CFORM disk contained a fairly extensive list of MFM and RLL drives and their parameters. Maybe see if your drive's characteristics match what's documented and for bonus points, scan through the list to see if there are any others with odd head numbers?



#6 BeeryMiller OFFLINE  

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Posted Thu Sep 27, 2018 9:48 AM

Here are some hard drive settings from the 80's.

Attached Files



#7 Schmitzi OFFLINE  

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Posted Thu Sep 27, 2018 12:15 PM

Back in the day, I started with Type 2   :lust:



#8 OLD CS1 OFFLINE  

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Posted Thu Sep 27, 2018 12:27 PM

Not certain about drives of the era, but I have seen plenty of SCSI and IDE drives which have an odd number of heads.  Open some up and you will see an even number of arms but with one arm missing a head assembly and that side of the platter may or may not have a recording layer on it.



#9 mizapf OFFLINE  

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Posted Thu Sep 27, 2018 1:26 PM

Note that SCSI and IDE drives have a virtual geometry, hiding the real one, to allow for zone recording and better usage of the value spaces for cylinders, head, and sectors per track. But you seem to refer to the real geometry, right?






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