Myarc HFDC MFM formatting

[+9640News]

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

 

[+Schmitzi]

*burp* aah *bump*

[+mizapf]

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

[RickyDean]

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.com/ref/hdd/op/heads/opNumber-c.html

 

http://www.pcguide.com/ref/hdd/op/mediaNumber-c.html

[+InsaneMultitasker]

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?

[+9640News]

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

[+Schmitzi]

Back in the day, I started with Type 2

[+OLD CS1]

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.

[+mizapf]

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?

[Brufnus]

On 9/27/2018 at 5:41 PM, InsaneMultitasker said:

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?

I have a couple of odd headed MFM drives.... a Rodime and a Toshiba with 7 heads, and two Seagate ST-1100 with 9 heads. So yes, they exist.

Edited September 16, 2022 by Brufnus