Q-bus to CF [was: IOmega]

[Allison]

>
>Subject: Re: Q-bus to CF   [was:  IOmega]
>   From: der Mouse <mouse at Rodents.Montreal.QC.CA>
>   Date: Fri, 29 Feb 2008 02:00:53 -0500 (EST)
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>> Generally IDE and CF (compactflash) are the same interface and for
>> Qbus-11 fairly simple.  It's been done, however, the problem is the
>> driver as bare IDE or CF is NOT MSCP not is it DL, DX, DY or RK so a
>> driver is needed and noone has apparently stepped up to do it.
>
>Not quite true.
>
>Some time back (years), someone was working on an IDE interface for a
>Qbus MicroVAX and I was doing the driver.  (This was not bootable; the
>idea was to netboot to get the kernel onto the machine.)
>
>We never got it working, and it is not clear to me, now, why not.  I'm
>not sure whether this is because it wasn't clear why then or because my
>wetware memory has bitrotted - what memory I have indicates that there
>were hardware issues, but I had no physical access to the hardware, so
>I'm not sure that that's right even aside from bitrotted memory.

the likely reason is PDP-11 and VAX does read before write and IDE
does not like that.  The fis is to make the READ address different 
from the write addresses, even DEC did that with interfaces.

It is otherwise straightfoward with the usual observance for timing and 
the like.

Allison

>I once was one of two people who built a one-off Qbus board out of
>wirewrap, so I feel I ought to be able to build such a thing myself.
>Perhaps someday I'll gather the parts and try it.  (Anyone have a Qbus
>development board looking for a home? :)
>
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