The *meow* auction we've all been waiting for *meow*

Chuck Guzis cclist at
Wed Dec 27 00:53:54 CST 2006

On 26 Dec 2006 at 22:15, dwight elvey wrote:

> This may only be an issue for formatting. Normally the drive has to be
> spinning for some time to get the controller to lock well enough to
> read the headers. The MSX may be different than the Canon Cat in this
> respect but since there is only the one drive, I'd suspect that one
> might even be able to just tie off the ready line. Many machines just
> do some delay after issuing the motor to start. I do like the idea of
> something that watched the index pulses. Something with a 555 chip
> might work or a 123 or like. 

It depends on the disk driver.  Some drivers may decide to proceed on 
READY present and hang if there's READY without a disk in the drive.  
BTW, this is why the 765 on the PC has a software reset line--since 
the drives don't have a READY status, the 765 will hang if no index 
pulses are there.  But if your driver doesn't put a deadman timer on 
the chip operations, your system could sit waiting for a diskette 

> I've been told that there are a few that don't support the 720KB.
> I'm not sure what tyhe difference is for the drive. The rpm isn't changed,
> just that they use FM instead of MFM. It might be that they change the
> size of the read data pulse or something. Pin 2 is a high density select
> so it must do something?

The drives used on the PS/2 don't use the window in the diskette 
jacket to switch denisty, but rather the host signal on pin 2.  But 
there, all it takes is jumpering the pin correctly to do 720K.  Most 
other drives use the window to specify density.


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