IDE <-> MFM

Tony Duell ard at p850ug1.demon.co.uk
Thu Nov 27 13:35:41 CST 2008


> 
> On Wed, 26 Nov 2008, Jules Richardson wrote:
> > Fred Cisin wrote:
> >> IIRC, my Compaq "Portable 286" (NOT the "Portable 2")
> >> had a pre-standardization ISA IDE "controller" that cabled to a bridge
> >> board on an MFM drive
> >
> > Isn't that the other way around, though: IDE controller -> bridge -> MFM 
> > drive?  The previous poster's saying* they're doing this the other way
> 
> That doesn't make sense. IDE stands for Integrated Drive Electronics, 
> which means that the controller is located on the drive. Therefore IDE 
> controller cards don't exist, and you can't bride IDE to an ST-412 

OK, but IDE bus interface cards do exist. Meaning cards that link ISA 
(or whatever) bus to an IDE drive. For ISA, it's little more than an 
address decoder and buffers (I happen to be using one in this PC). 

> interface type drive.

Sure you can. Make a PCB containing a WD1003-like disk controller. On one 
side, have ST412 connectors to conencto to that sort of drive. On the 
other, have an IDE interface -- data lines, 3 address lines, etc. In 
other words the original PC/AT disk controller board minus the floppy 
controller and minus most of the address decoder. Linked to the IDE bus 
interface I mentioned just now, you have a complete ST412 hard disk 
controller system. And the seond part of it could reasonably be called an 
IDE (host interface) to ST412 (drive interface) bridge board.

-tony




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