RE: RE: 3.3 Volts and PMC Modules

[Lame Brooks-G14738 <brooks.lame@motorola.com>]

Actually, I think the PMC spec is independent of the PCI spec revision.  IE,
it doesn't _require_ any particular rev of the PCI spec; rather, it requires
that the PMC and baseboard equipment vendors document what version of PCI
spec they meet and whether or not 3.3v is required/supplied.  I would hazard
to say that the vast majority of new baseboard PMC equipment will supply
3.3v.  
-- BrooksL

..snip..
> So even though PCIv2.2 requires 3.3V, the current PMC
> specification only requires PCIv2.0 compliance, and
> does not require 3.3V to be present.
> 
> I have seen CPU boards with PMC slots without 3.3V.
> 
> We still put 3.3V regulators on our PMC boards.
> 
> imho, not requiring 3.3V on PMC slots from the beginning
> was NOT a good idea. The small PMC cards can already have
> enough heat dissipation problems without having to dump
> heat from regulators, not to mention the wasted space.
> But, can not change the past, PMC boards need 3.3V
> regulators if they are to work in arbitrary PMC slots.
> 
> Ivor
> 
> At 02:50 PM 3/22/00 -0800, you wrote:
> >I quickly scanned the PMC spec (IEEE P1386.1) draft 2.0 and 
> found only that
> >the electrical and logical layers are defined by the PCI 
> spec (revision
> >independent).  The PMC spec was written when PCI 2.0 was 
> current and which
> >does not require 3.3v on a 5v slot.  However, PCI 2.2 is now 
> the current
> >revision and that does require 3.3v on all PCI slots.  
> Regardless, in the
> >PMC spec, under section 4.1 'Conformance', it states "the 
> vendor claiming
> >compliance shall specify in the product specifications, 
> those areas of
> >compliance where optional features are allowed."  PCI spec 
> revision and/or
> >availability of 3.3v, falls under this product documentation 
> requirement.
> >-- BrooksL
> >
> >> -----Original Message-----
> >> From: Louis Przebienda [mailto:lprzebienda@acromag.com]
> >> Sent: Wednesday, 22 March, 2000 12:42
> >> To: pci-sig@znyx.com
> >> Subject: 3.3 Volts and PMC Modules
> >> 
> >> 
> >> Hello All,
> >> 
> >> Do PMC modules provide their own 3.3 volts onboard via an 
> >> onboard regulator,
> >> or do they rely upon the cards they plug into to provide 3.3 volts?
> >> 
> >> For those who have designed PMC modules, what did you do?
> >> 
> >> For those that have designed cards with PMC module slots, do 
> >> you provide 3.3
> >> volts to the PMC module slots?
> >> 
> >> The Electrical Specification for Common Mezzanine Card 
> >> P1386/Draft2.1 dated
> >> 11-Oct-99 in paragraph 6.1 states :"The CMC standard allows 
> >> +5V, +3.3V and
> >> +/-12V.  Which of these voltages shall be provided is 
> defined in the
> >> specific bus standard:".  The bus standard is the PCI bus 
> >> spec.  As we know
> >> PCI 2.1 spec did not require the 3.3V power pins to be driven. 
> >> 
> >> I would be grateful for any comments, experiences or 
> insight into this
> >> matter.
> >> 
> >> Thank you for you assistance.
> >> 
> >> Louis Przebienda
> >> Designs Engineer
> >> Acromag Inc.
> >> Email: lprzebienda@acromag.com
> >> 
> >> 
> >
> >
> >
>