At 09:17 PM 8/17/98 , Jay Maynard wrote:
>On Mon, Aug 17, 1998 at 03:11:29PM -0700, Matt Thomas wrote:
>> 1) It may seem trivial but it would be nice instead of backplane0,
>>    mainbus0 was used (like most other ports).  Mostly for consistency
>>    but also because I don't consider the latter VAXen to have 
>>    backplanes (that a big iron concept).
>
>This is a nit. What difference does it make what name you hang on
>it?...especially since the 4000/300 does indeed have a backplane...
>
>> 2) Nuke vsbus.  On the {MV,VS}2000/3100/4000, just connect the
>>    devices to mainbus0.  For example the VS4000/60 would be:
>> 	mainbus0	at root
>> 	le*		at mainbus?
>> 	asc*		at mainbus?
>> 	dz*		at mainbus?
>> 	audioamd*	at mainbus?
>
>This has rather serious implications for my work on the 4000/300. The KA670
>has none of the things you mention, but it does have one SGEC (second
>generation Ethernet controller) device and two SHAC (shared host access
>controller) devices which live on the CPU card and require nothing in the
>way of bus support, unlike the vsbus devices in the other VAXstations. At
>Ragge's suggestion, I went about it by implementing a minimalist bus, the
>mvbus, that does nothing except serve as a place to connect things. It would
>be simple enough to do away with that and connect ze0 at backplane0, but is
>that a Good Thing, and why?

It reduces complexity (which is good).  There shouldn't be that much work
to switch to a mainbus instead of the mvbus you are using now.

>> I know the above is a lot of work, but it really is required to 
>> fully support the latter VAXen models.
>
>Is it? How come? I'd really like to not have to overhaul the device driver
>in the middle of writing it...

The SGEC and SHAC are also used on the DECsystem 5500 and it would be a shame if
your drivers couldn't be used there.
-- 
Matt Thomas               Internet:   matt@3am-software.com
3am Software Foundry      WWW URL:    http://www.3am-software.com/bio/matt/
Sunnyvale, CA             Disclaimer: I avow all knowledge of this message