Tandem Minicomputers

jim stephens jwsmail at jwsss.com
Mon Sep 30 15:07:49 CDT 2019

On 9/30/2019 9:39 AM, Paul Berger via cctalk wrote:
> On 2019-09-30 1:27 p.m., Diane Bruce via cctalk wrote:
>> On Mon, Sep 30, 2019 at 10:57:25AM -0500, Jon Elson via cctalk wrote:
>>> On 09/29/2019 11:46 PM, Jason T via cctalk wrote:
>>>> Well I said no more computers I can't lift, but exotic systems keep
>>>> finding me.  So today we pulled a Tandem CLX out of a basement, along
>>>> with a few boxes of docs, 9-track tapes and random odd and ends:
>>>> https://photos.app.goo.gl/m2N7RKN3JXcmVTUC8
>>>> There's such as thing as "so obscure that no one knows/cares about
>>>> it".  I've had those before.  Do I have another?  It sure is heavy.
>>>> -j
>>> Tandem was hot stuff back in the 1980's.  These appear to be
>>> the last gasp of their technology.
>> I remember hearing that the credit/debit card database we were talking
>> to was a Royal Bank Tandem in Toronto when I was first involved
>> with Point of Sale protocols.
> All of the Canadian banks used Tandem systems to front end the 
> Interact it was part of the initial plan for that system.
> Paul.
>>> Once you had fast networking between processors, the whole
>>> Tandem concept became pretty easy to do on a few ordinary
>>> processors, without special hardware.  So, their whole
>>> reason for being became moot.
>> Indeed.
> Yes I suspect anything that HP may flog as nonstop these days would be 
> a high availability cluster which would probably include shared 
> storage.  SAN has made shared storage trivial and even allows you to 
> spread the nodes in the cluster geographically. When I first 
> encountered HA cluster the shared storage was parallel SCSI with an 
> initiator in each system.  The first that aloowed you to spread the 
> nodes enough to have them in different building used IBM's SSA, a 
> predecessor of SAN, to connect the storage.
In the early 2000s, I visited the HP site which had the developers for 
the Tandem product, VMS HP/UX.  They were using our ICE for development 
of the Itanium versions of VMS and for HP/UX.  I don't think there was 
any plan to support the Nonstop in such a fashion, but the developers 
were all there @ the same Cupertino site.

As to developing something to do a useful version of TAL and Nonstop w/o 
any specialized hardware, I don't think so.  We had a system which was 
used for a port of the Ultimate / Pick system to Tandem, which was 
eventually shutdown and abandoned, but going the other way, to run TAL 
in any useful manner without the checkpointing would be pretty much useless.

And Stratus is still there with financial industry using it heavily.

The Tandem method used a checkpointing comparison method which had to 
use TAL as the basic platform.  Periodically comparisons would be 
performed, but there was more than a little computing between comparison 
checkpoints.  And the voting out of a failed unit was done by hardware.

Stratus used a bus version. so they could have hardware pulled and their 
loss was in a few microseconds.  For the realtime trader guys Stratus 
always won over Tandem.  but where there was no need, either platform 
was excellent as pointed out for recovering and continuing after a failure.

Also, I don't know if Tandem had it, but Stratus had serial connections 
and gizmos which would allow Session protection on a terminal.  you 
could cut one or the other connection from your computer (required 2) 
and not miss a beat on a terminal.  If the terminal went black though 
there were not as many options.


>>> Jon
>> Diane
> Paul.

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