VAX 780 on eBay

Paul Koning paulkoning at
Mon Jan 3 15:23:55 CST 2022

> On Jan 3, 2022, at 3:36 PM, Chuck Guzis via cctalk <cctalk at> wrote:
> On 1/3/22 10:58 AM, Paul Koning via cctalk wrote:
>> The discussion about 3-phase made me check some documentation.
>> I also looked at some CDC 6000 series docs.  Those used 400 Hz 3 phase for supplying the CPU and peripheral logic.  The CPU cabinets also take 3 phase mains power for the  compressors (for the Freon cooling system).  Curiously, the 1964-era 6603 disk drive uses only 400 Hz power.  I wonder if that feeds the spindle motor, or if that was a DC motor?  And the 626 tape drive wants 3-phase mains power.
> Are you certain about that?  The '66 document for the Bryant series I
> drives/6603
> on page 1-3 mentions 280/440 3-phase just for the spindle motor (5 or 10
> hp, depending on number of disks).   The hydraulic pump had its own
> 3-phase motor.  I think the 6603 electronics were 400Hz.   Serious
> current draw on those motor lines too--the Series II shows power
> consumption draw at 280VAC--somewhere around 50A.

I forgot that drive was Bryant.  The 400 Hz only information comes from the 6000 Site Prep manual, so I guess they got it wrong.

> I remember the leak jugs--and the hydraulic fluid that occasionally made
> it onto the floor.  An operator at SVLOPS made a dash to take care of a
> 501 printer and slipped and fell in a puddle of the stuff.  It was funny
> at the time...
> The old 808/6638 drives, which displaced the 6603, similarly used 280V
> 3-phase for the 5 hp spindle motor and hydraulic pump and 440Hz for the
> electronics.

The only hydraulic actuator drive I ever saw in person was an IBM 1311.  Found out when it sprang a leak and sprayed hydraulic oil all over the boot pack.  FE guy cleaned everything (heads, pack, etc.), fixed the seal and bled the system, and it all worked afterwards.  No damage to the pack.  

The 6603 is highly unusual because it has 12 bit parallel data flow, rather than bit-serial as everyone else did (until Cray went back to parallel with the Cray 1, if I remember right).  That made the 6603 very much faster, as far as data throughput goes, than any other drive for quite a number of years.  It also has variable sector counts depending on cylinder number, which came back a long time later.  And it has a rotating head actuator rather than linear motion, just as recent hard drives do.


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