async designs

CRC technobug at
Sun Aug 13 01:08:13 CDT 2006

On Fri, 11 Aug 2006 12:58:56 -0700, Brent Hilpert <hilpert at>  

>> Chuck Guzis wrote:
>>>   At one time async logic was a hot topic.
>> The IAS machine (von Neumann/late 1940s) is listed in various  
>> places (under
>> 'clock rate') as being 'async'. (And - annoyingly - those listings  
>> then don't
>> provide an effective instruction rate for the sake of comparison).
>> I've been curious as to more precisely how the timing was  
>> accomplished in that
>> (those) machines. Offhand, I suspect you still end up with delay  
>> elements in
>> the design at various points to ensure some group (worst case) of
>> signals/paths
>> are all ready/stable at some point and you end with a more-or-less  
>> 'effective
>> clock rate' anyways and don't gain much.
>> Such all started with ENIAC didn't it?, which - based on what I've  
>> been able
>> to find/read - could be described as an async design.
>> Was async still being discussed in the 60's?

Serious theoretical work was done for relay logic prior to ENIAC and  
it definitely isn't dead right now. There is a substantial amount of  
work being done in the area with the UK being a hotspot of activity.  
Early this year ARM and a Philips subsidiary released an ARM core  
that was entirely async. For those interested, this is an excellent  


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