Indeed, I can see that, but the MicroVAX 2000 firmware manages to work it
out somehow, I just don't know how. The difference between the RD53 and RD54
seems to be entirely in the number of heads, so my guess is it tries to
detect the number of heads somehow. Of course it may do something completely
different, I don't know.
Regards
Rob
-----Original Message-----
From: cctalk-bounces at
classiccmp.org [mailto:cctalk-
bounces at
classiccmp.org] On Behalf Of Tom Gardner
Sent: 04 January 2014 17:19
To: 'General Discussion: On-Topic and Off-Topic Posts'
Subject: RE: MFM Control Signals and RD disk size
There is nothing in a standard disk drive MFM interface that signals the
drive
size. This is almost always a jumper setting and
almost always on the
controller; one set of jumpers for each drive controlled. If the
controller also
has some BIOS on it, it could be a BIOS jumper
setting.
Tom
> -----Original Message-----
> From: Robert Jarratt [mailto:robert.jarratt at
ntlworld.com]
> Sent: Saturday, January 04, 2014 3:36 AM
> To: General Discussion: On-Topic and Off-Topic Posts; DEC discussion
list.
Subject: MFM
Control Signals and RD disk size
As I don't have a logic analyser to help me with my analysis of the
MFM interface, can anyone tell me how the MicroVAX 2000 determines
disk size?
> I
> know it is related to the number of heads, but what does the drive do
> when the host asks for a head that does not exist? How does it report
> this back?
> The only thing I can think of is the Ready signal, could that be it?
>
>
>
> Regards
>
>
>
> Rob
>