With your current wattage figures, I'd definitely go with a beefier power supply. Older PSUs aren't very power efficient, and the figures you're quoting come very close to the theoretical limit, though in practical terms you're probably overstepping the limit.

The wattage for the CDROM and the hard drive seem pretty high, but maybe they're realistic for a momentary peak. But in steady operation I wouldn't expect them to use 25W. Maybe more like half that.

One important concern that's not easy to account for is that the load is divided into different output rails. Even if you don't exceed the total wattage limit, one rail might be overloaded while another is not. Also, it's always pretty difficult or impossible to make an accurate prediction of how much power each component will actually use. Guidelines and reality can be very different. The online PSU calculators do their best to help but they're of limited value.

I'd prefer a higher rated PSU if possible. If you decide to try the 130W, I'd try to measure the outputs with a multimeter and see how they look while the system is running and under stress. If they're sagging it's a sign you may be overstressing it. I'd be nervous about it without some measurements.

I think that calculator is dramatically liberal in its power estimates - the first example that I noted was looking in the CPUs, it lists Socket 478 Willamette chips at 100W; none of them hit that on their worst day (the "top dog" 2GHz is 72-73W per Intel's specifications; most of them are more 50-60W range). Just to further explore this example I plugged in my P4 system to this calculator as accurately as I could, and it spit out 289W. The Outervision calculator estimated 214W. Real-world measurement of that system has boot-up power draw at around 130W, and desktop idle at around 100W - running 3D01SE Game 4 in a loop it pulls around 190W. These are "at the wall" numbers though - knock 20-25% off and that's what's actually being drawn as DC on the PSU.

My point is - even running a relatively complex looped load my system doesn't even approach half of what that calculator says it should. I wouldn't trust that calculator as a result. (and to beat on this a little further, I do have a system that actually can draw 289W (or more) from the wall - it has four GeForce 7s and a dual-core CPU in it).

Some questions I'd have regarding your build: are you certain the speakers' amplifier is drawing power from the system's PSU? And if so, can you re-configure it to draw power externally? (amplifiers tend to be pretty inefficient, and I see no reason to draw all that waste through the PC's PSU if it can be avoided)

mr_bigmouth_502: The efficiency of the PSU won't be a problem on the DC side unless it's lying in its ratings. It just means more power is wasted at the wall and more heat has to be dealt with. Given that we're talking about relatively small figures all around here, it's nothing I'd be terribly worried about (it isn't like modern 1200W monsters).

I have this system:
CPU: Intel Pentium 166 MMX
Mainboard: Gigabyte GA-586HX
RAM: 384 MB EDO PS/2 SIMMs
Graphics card: Elsa Victory Erazor (Riva 128 with 4 MB SGRAM and TV In/Out), 3Dfx Voodoo 1
Network card: Realtek 8139C / 100 MBit/s
Soundcards: Guillemot Maxi Sound 64 Home Studio with Yamaha DB60XG wavetable, Primax Altrasound
Controller: Highpoint HPT370/372 UDMA controller
HDD: IBM-DJNA-351520, IBM-DTLA-305040
CD: Pioneer DVD-A04SZ Slot-In drive
Disk: 3.5" and 5.25" drive

It draws between 26 and 28W in operation.

Maybe it's time for a new PC power consumption calculator website specializing in retro parts... that would be a good VOGONS member project. 😀

What current rating does the psu have?
I think youre good as to use a mobo setup with cards, a hdd and cdrom, should be no problem.
Only if youre going to use 2x cdrom drives or 4 harddrives, you may suffer problems.
IBM power supply should relatively reliable and protected against overcurrent.

mr_bigmouth_502 wrote:

With your current wattage figures, I'd definitely go with a beefier power supply. Older PSUs aren't very power efficient, and the figures you're quoting come very close to the theoretical limit, though in practical terms you're probably overstepping the limit.

I often see that mistake.
It is not true.
A 130W PSU will give 130W.
Efficiency will change how much is taken from the wall, not how much it gives.

In other words, the psu is capable to supply 130w, in a 5v and 12v special kind of balance, but it could take up as much as 200w from the outlet depending on the maximum load and power supply efficiency.
As most drives can use as much as 1amp from the 12v line, when idling or normal load it does not reacht that, only when it is starting causing some peak currents.

Youre safe to go with 130w psu, don't let others scare you.

JaNoZ wrote:

IBM power supply should relatively reliable and protected against overcurrent.

I agree an IBM probably has good protection, but I don't think those protections perfectly protect a PSU, at least that's been my experience. I had one heavily built PSU which tripped it's overload protection many times running a test bench. Finally one day I turned it on and it popped like a grenade. It finally just had enough abuse. It didn't hurt the board but the PSU was done.
One of my AcBel OEM supplies from a Sun workstation slowly lost it's 3.3v rail due to an overload on that rail. It took weeks for that to happen, but the 3.3v rail ended up ruined over the long term.
Granted this is a sample size of only 2, but the impression this has left is that PSU protections can't be taken for granted against long term, repeated events.

There probably wouldn't be any such problem in this case. Certainly the sustained draw wouldn't be even half of 130W. But the momentary worst case peaks on each rail, versus the corresponding limits, I'm not sure about.

But most PSUs can absorb over limit peaks reasonably well as long as the average is plenty below the limit and the peaks aren't SUPER high
Short peaks are absorbed by the output capacitors

obobskivich wrote:

Some questions I'd have regarding your build: are you certain the speakers' amplifier is drawing power from the system's PSU? And if so, can you re-configure it to draw power externally? (amplifiers tend to be pretty inefficient, and I see no reason to draw all that waste through the PC's PSU if it can be avoided)

Thanks for the replies so far. It draws power from a 3.5 floppy connecter. Probably hooking it to an external AT psu with the floppy power routed back into the PC is the only way to make it work. I'd rather just save 20W by not using the speakers, then I should be at a safe distance from the 130W limit? Kinda thinking about taking out the CD drive too and using my external powered parallel port version if necessary.

Some of you say the system will not draw close to 130W, I think I should play it safe and lighten the load.

I have never seen speakers that fit in a floppy bay like that. If you have those pic please.
But you would be much better off with normal external speakers with separate power supplies.

They are like this and have a floppy power plug on the back, as well as an analog audio cable that plugs into the back of the sound card. I meant 5.25 bay speakers. oops

My Vectra has 120W PSU and works flawlessly with 5 expansion components (3 sound cards), SCSI hard disk with 8 platters, SCSI CD-ROM and 3.5" floppy.

JaNoZ wrote:

In other words, the psu is capable to supply 130w, in a 5v and 12v special kind of balance, but it could take up as much as 200w from the outlet depending on the maximum load and power supply efficiency.
As most drives can use as much as 1amp from the 12v line, when idling or normal load it does not reacht that, only when it is starting causing some peak currents.

Youre safe to go with 130w psu, don't let others scare you.

Cool. I never knew that. 😉

computergeek92 wrote:

Thanks for the replies so far. It draws power from a 3.5 floppy connecter. Probably hooking it to an external AT psu with the floppy power routed back into the PC is the only way to make it work. I'd rather just save 20W by not using the speakers, then I should be at a safe distance from the 130W limit? Kinda thinking about taking out the CD drive too and using my external powered parallel port version if necessary.

Some of you say the system will not draw close to 130W, I think I should play it safe and lighten the load.

Trust us - you won't approach 130W at the wall here. Let alone internally. The speakers drawing power thru a floppy connector mean they really won't draw that much power (the connector isn't rated for all that much power) - 20W is probably end of the world for them (as in, they'll blow up soon enough so you don't need to worry about the load). Real-life is probably like 1-2W/ch and that probably sounds pretty bad. 😊

If you're really hesitant about this (and honestly, having looked at that "calculator" again, I just see it as a Weapon of Mass FUD), get an AC meter and boot the thing up with the expansion cards, disks, etc out (just the motherboard, RAM, CPU - it should beep at you) and see what it says. I doubt even with everything you've got planned it will be running close to 50W.

On the speakers - I'd probably consider getting external speakers unless you really need the space saver. Those bay devices were never very good in terms of fidelity from what I recall. 😒