Skipaiotter wrote:
> Thinking on upgrading PC and was looking at the following cards?
>
> MSI 8600GT Silent 256mb pci-e graphics card
> XFX 8600GT Extreme 256mb pci-e graphics card
> XFX 8800GT Alpha Dog Edition 512mb pci-e graphics card
>
> The main problem is working out if my old PSU is able to run any of the
> above which is a -VHB(G) PSU (480watts)
>
> Specs:
>
> Total power = 480w
> Max current 12v rail 1 = 16A
> Max current 12v rail 2 = 15A
> Max current 5v rail = 40A
> Max current 3.3v = 34A
>
> Connectors
>
> Standard peripheral = 7
> Floppy = 2
> Serial ATA = 6
> 6 pin PEG = 1
> Mainboard = 20/24 pin
> 4 pin cpu = yes
> 8 pin cpu = no
>
> I'm thinking of having a AM2 board with 64x2 6000+, 2gb ddr2 800 ram.
>
> And then use from old computer, the x-fi platnium, 160gb ide drive and
> lg cd/dvd rewriter ide and floppy. I also getting a Aplus Monolize case
> with 2 x 25cm fans (Mabbe 2 x 120mm fans if I install them.)
>
> Can I get away with running a single 8600 or single 8800?
>
> Or to run a 8800, do I need a better psu than what I have?
>
You missed the brand name on that supply. It sounds like it is an Enermax.
http://www.aone.co.uk/ProdInfo.ASP?ProductID=18
+3.3V @ 34A, +5V @ 40A, +12V1 @ 16A, +12V2 @ 15A, -12V @ 0.8A, +5Vsb @ 2.5A
+3.3V & +5V max 280W load
all rails max 480W load
There are two 12V rails. 12V2 powers the processor, via the ATX12V 2x2 connector.
A 6000+ processor is 125W, 125W/12V * (1/0.90) = 11.6A at assumed 90% Vcore efficiency.
That means the 12V2 at 16 amps, is enough for the 11.6A load.
12V1 powers everything else.
The 8800GT power is listed here, and varies depending on the card. The reference
8800GT is 78W, while I think the card being reviewed was an overclocked card,
and it measured 85.7W. Taking the latter figure, 85.7W/12V = 7.14A
http://www.xbitlabs.com/articles/video/display/gainward-bliss-8800gt_5.html
Other loads contributing to 12V1 would be 0.6A for HDD, 1.5A for CDROM (when
media is present), and 0.5A for cooling fans (check the label on the fans for
a more exact number). (A separate calculation for spinup current on a HDD,
is only needed if the user plans on using a lot of drives.)
Total 12V1 = 7.14 + 0.6 + 1.5 + 0.5 = 9.74A (of the available 15A)
To work out total system power, I use 50W for the motherboard and RAM. This is
based on measuring only two motherboards that I own, as it is not possible
to figure out otherwise, what sort of power a motherboard draws. Most of
the power would be in the Northbridge, and some of those burn up 20W or more.
RAM is pretty low these days, at maybe 3W a stick. Some power sites give
higher numbers for RAM. You can download a Kingston datasheet, to verify
what a typical number for RAM should be. So I just lump all that stuff
together and call it 50W, without really knowing whether it is coming
from the 3.3V or 5V rail. The above Enermax spec has plenty of room on
those two rails, to run a modern motherboard.
Total system power estimate = 12V * (11.6 + 9.74) + 50W (mobo/RAM) + 10W (+5VSB)
= 316W
That fits comfortably under the 480W limit.
There is a review of the supply here, that says it doesn't like a full load
on the 12V rail. The efficiency of the supply is around 77.2% at 75% loading,
so at 316W, the total wall plug power is 316/0.772 = 409.3W. Heat pouring from
the supply will be 409.3 - 316 = 93.3W. The more efficient the supply, the
less waste heat. The best expensive supplies now, can achieve 85% or so
for efficiency. (The load is only going to be 316W while gaming, with a CD
in the drive, and will be a lot less at idle.)
http://www.trustedreviews.com/peripherals/review/2005/02/08/ATX-Power-...ply-Gro
The 11.6 + 9.74 amp loading on the 12V rail, represents 68.8% of the
available 31A total. The graphs here, show the Coolergiant 485 is still
operating normally at the 75% loading point for the 12V rails, but shuts
off at 100%. So you're still fine, by the looks of it.
http://www.trustedreviews.com/peripherals/review/2005/02/08/ATX-Power-...ply-Gro
So really, it is a coin toss, as to whether it is worthwhile to replace the
supply. If the supply has given previous signs of being "tired", then
you might consider replacing it. If it is still well behaved, you
could still use it if you want.
With regard to supplies blowing up, yes, they can take out expensive
components. But modern supplies are getting better, in terms of failure
characteristics. For example, some of the Bestec supplies used in
some older Emachines, I've read, are virtually guaranteed to take
out the motherboard when they die. But a lot of other people survive
a supply failure, so more modern supplies won't be quite as bad
for that kind of thing.
If the supply shows any signs of not liking the load, then don't
torture it. I hate reading accounts, where a person says "I couldn't
get it to start, so I flipped the on-off switch like 50 times,
and all of a sudden smoke came out". Doing something like that
is just dumb. If the supply detects a fault, and stops, then don't
press your luck
Have fun,
Paul
>> Stay informed about: 480w PSU requirements for 8600 or 8800 enquiry 
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