idea for a universal disk interface

[Tom Gardner]

-----Original Message-----
From: ben [mailto:bfranchuk at jetnet.ab.ca] 
Sent: Saturday, April 16, 2022 1:39 PM
To: cctalk at classiccmp.org
Subject: Re: idea for a universal disk interface

On 2022-04-16 1:13 p.m., Tom Gardner via cctalk wrote:
<snip> 
> Tom
> 
How do you handle the disk hardware timing, power up, seek and disk RPM?. Ben.
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Those really shouldn't be any problem. 

RPM is data rate but unlike the disk drive the RPM and the data rate in an emulator are as precise as the crystal and hardware setting the data rate- no jitter, speed variation etc.  Everything is on time
The emulator would have to generate a synthetic Index signal (and sectors for hard sectored controllers) to keep the controller happy but that is just counting off a clock.

Power up - most drives tell the controller when they are ready but some have a start/stop controls.  Regardless, it is pretty easy for the emulator to respond to any commands and present appropriate status.  It doesn't have to wait for a disk pack to spin up - as soon as it gets a start command it can present ready status.

It would have to generate a home signal but all that means is the data pointer is pointing to the memory location of the first byte of the first track (Track 00 head 00)

Seeks are near instantaneous - the controller issues the seek command and after a minimum delay the emulator presents ready status

The only thing the emulator really has to worry about is too quick responses breaking the controller