Its not the console, its the cpu.  the 21164 comes in several flavors.
Check Digital's site under semiconductor, where you will find data sheets.

Also there was some discussion of this recently on axp-list@redhat.com

On Wed, 6 Aug 1997, Andrew Gallatin wrote:

> 
> Matthew Jacob writes:
>  > 
>  > 
>  > However, you *can* get SRM for the AlphaPC164, and I've found
>  > the board to be quite nice. I've been running off a system
>  > I purchased from Aspen Systems for some months now and have
>  > had no problems with it.
> 
> Might the type of CPU also be an issue now as well?
> 
> A week or two ago, there was somebody saying he had an AlphaPC164 
> and that an older 433Mhz cpu worked just fine, but that a newer 'NT
> designated  500Mhz cpu wouldn't boot with the SRM firmware, but it
> would boot with the NT Arc/AlphaBios console.
> 
> Did anybody ever determine if the SRM console now has some sort of
> hack in it which causes it to punt when it detects that it was booted
> on a 'NT-designated' CPU?  If so, you might end up having to pay 3 or
> 4 times as much to get a Digital UNIX designated CPU.. Sigh..
> 
> Drew
> 
> ------------------------------------------------------------------------------
> Andrew Gallatin				http://www.cs.duke.edu/~gallatin
> Duke University				Email:		gallatin@cs.duke.edu
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>