[Info-vax] OT: the Daily WTF for today is a VAX/VMS story

[William Pechter]

In article <n9r6m6$4ed$1 at Iltempo.Update.UU.SE>,
Johnny Billquist  <bqt at softjar.se> wrote:
>On 2016-02-15 01:28, Kerry Main wrote:
>>> -----Original Message-----
>>> From: Info-vax [mailto:info-vax-bounces at info-vax.com] On Behalf Of
>>> Johnny Billquist via Info-vax
>>> Sent: 14-Feb-16 6:50 PM
>>> To: info-vax at info-vax.com
>>> Cc: Johnny Billquist <bqt at softjar.se>
>>> Subject: Re: [New Info-vax] OT: the Daily WTF for today is a VAX/VMS
>>> story
>>>
>>> On 2016-02-15 00:05, William Pechter wrote:
>>>> Yup and the RP06's could even share a power socket with a cable DEC
>>> shipped
>>>> that let a pair of drives daisy-chain the AC power between them.
>>>>
>>>> And a power sequence cable kept them from trying to power up at the
>>> same time
>>>> IIRC...
>>>
>>> You know, I've never seen a power sequence cable for the RP06, but
>>> when
>>> I was reading the documentation now, the manual mentions the power
>>> sequence control. So obviously there must have been a way to connect
>>> them together for that purpose.
>>>
>>> Our DEC-2060 had three RP06, but I cannot remember any power
>>> sequencing
>>> going on between them. But maybe 3 was considered too few. Or,
>>> actually,
>>> I think we also had them all on separate fuses...
>>>
>>> 	Johnny
>>>
>>
>> There was a small 2 or 3 pin signal cable which was strung between
>> drive power controllers to enable power-up sequencing.
>>
>> It was highly recommended best practice, but not mandatory. This was
>> not unique to RP's, but was actually used by RMxx/RAxx and numerous
>> other drives at the time. I believe you could setup systems powering on
>> the same way.
>>
>> Reason was that these drives had very high startup current and after a
>> computer room power failure or just normal power off /on maint work,
>> if this sequencing was not in place, then the Data Center UPS/PDS's
>> breakers might not be able to deal with the current from all the drives
>> restarting at once.
>
>I'm well aware of them for the RA60/80/81/82, and I mentioned them in a 
>previous post. But I never saw anything similar for the RP06. But 
>something obviously existed, as the manual refers to it. I just never 
>saw/used any. I need to go and check an RP06 when I get close to them 
>next time, so see if I can find the connector.
>For the RA drives, you needed the terminator plug in order to even get 
>the drives to spin up. But they were also pretty obvious when you look 
>at the back of the drive.
>
>	Johnny
>
>-- 
>Johnny Billquist                  || "I'm on a bus
>                                   ||  on a psychedelic trip
>email: bqt at softjar.se             ||  Reading murder books
>pdp is alive!                     ||  tryin' to stay hip" - B. Idol

IIRC there was a small 3 pin molex jack on the DCL for that purpose
(or was it a 4 pin).

It wasn't used often -- unlike the sequence betweeen cpu and unibus
cabinets on 11s and Vaxes.

Bill

-- 
-- 
Digital had it then.  Don't you wish you could buy it now!
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