PSU efficiency ratings for the IBM PC and XT power supplies? 63/120 watt versions

[offensive_Jerk]

Does anyone know what the efficiency of the older IBM 5150/5160/5170 power supplies are, and what they would translate to in today's power supply ratings?

 

[pearce_jj]

At best 65%. SMPS were about 60/65 for ages. Probably with a power factor of about 0.65 as well.

In other words, awful.

 

[Chuck(G)]

You could test it yourself with a dummy load of known characteristics and a Kill-A-Watt.

My recollection is that PFs on these things were really awful.

 

[Dwight Elvey]

Since they run below their rated value, most of the time, their efficiency may be even lower.
Dwight

 

[pearce_jj]

Regulation on this came far too late IMO.

HP and I’m sure all the others were still selling servers with 65% efficient PSUs as late as 2010. The sheer waste in data centres is almost incomprehensible.

 

[Chuck(G)]

It's a matter of perspective. Compared to the old linear-with-transformer PSUs, the switchers were ahead in efficiency, not to mention sheer weight. I can recall seeing a pile of 5V 200A SMPSUs for sale at Halted and saying to myself "You've got to be kidding--a 200 amp power supply in that little case?". So perhaps we were blinded.

After all, it wasn't that many years prior that the power supply for much big iron was MG sets providing 400Hz 3-phase power. SMPSU design was a black art, according to comments I remember from Bob Boschert.