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Topic: Power CC - power supply loading (Read 173 times) |
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hobby
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Posts: 17
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Power CC - power supply loading
« on: Oct 23rd, 2002, 4:43am » |
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Here is a list of "assumed" loads - please feel free to add correction, clarification or missing information - this may be obvious to many, but it isn't to me and I think it may be helpfull to have it here for anyone who is making power supply decisions for power CCs.
cooling fan 1W
FDD 5W
HDD 5200RPM 10W, 7200 RPM 15W
CDrom 20W (if you squeeze one in)
PCI LB ~20-30W (need help here, info came from PC motherboard info w/o CPU or RAM - is this appropriate for my 6500 ?)
G3 L2 upgrade -  ? how much additional over the 6500?
typical PCI card 5W
modem (int or ext) powered by LB 5W
RAM - 10W/128MB (again got this from PC info)
color classic CRT - 50W? this is the big one, PC info says 15" monitor uses 85W
adding all of this up puts me right at 100W (rated CC PS) with a 6500, no upgrade, no PCI 64MB ram and HDD
can anyone add clarity to the CRT or the LB?
also can anyone comment on how much of the 6500LB power is consumed in the form of 3.3V vs 5V?
thanks for listening
mike
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Chris Lawson
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Re: Power CC - power supply loading
« Reply #1 on: Oct 23rd, 2002, 10:35am » |
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on Oct 23rd, 2002, 4:43am, hobby wrote:
Probably somewhat less, actually. Some have an actual rating on the casing; I think the stock fan in a CC is 12V @ about 0.05A, which would make it about 0.6W. 1W is probably close enough in this case, though.
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ISTR Apple's really really old Developer Notes (or maybe Inside Macintosh) have power draw specs for the floppy drive. 5W sounds reasonable to me but I should look it up in Inside Macintosh next time I'm home.
Quote:| HDD 5200RPM 10W, 7200 RPM 15W |
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Very dependent on the drive. Check the individual drive's ratings, because I've seen drives that were anywhere from about 5W to something near 35W, so high that an LC III couldn't kick-start one.
Quote:| CDrom 20W (if you squeeze one in) |
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Haven't checked my CD-ROM drive power ratings lately but this seems reasonable.
Quote:| modem (int or ext) powered by LB 5W |
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External modems can't draw any more than about 350 mA if they're powered by ADB and they can't be powered from the mobo in any other way, so unless it's an internal - and 5W is probably a decent estimate for that - it won't draw anything appreciable.
Quote:| RAM - 10W/128MB (again got this from PC info) |
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Be sure of what type of RAM that is. 3.3V will probably draw less power than the 5V DRAM required by the various Takky boards. Not many PCs used the 168-pin DIMMs that the Alchemy and Gazelle boards use, which makes for difficulty in comparison, I would guess.
Quote:| color classic CRT - 50W? this is the big one, PC info says 15" monitor uses 85W |
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Assuming CRT power draws scale roughly linearly, a 10" CRT should be about 2/3 of 85W, and I think 50W is probably a good enough estimate.
cl
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Chris Lawson
CC FAQ maintainer, general Mac guru
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hobby
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Re: Power CC - power supply loading
« Reply #2 on: Oct 24th, 2002, 8:55am » |
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Here's an update on loading:
found info that supports, the 603e CPU uses 3W
G3 L2 upgrade card uses 20 - 30W dependent on which model, and this is 3.3V
max PCI is 15W (x2) but two won't be used in the CC
FDD and ADB (external modem, etc) are trivial loads off of the LB
still very interested in identifying what the load of the 6500LB itself is, I am assuming around 20W ??
also interested in how the LB supports 3.3V supply, since it generates its own, is it a parrallel supply to external 3.3v connected, or does the LB 3.3 only support boot up & cache?
can I assume that is I supply 3.3V to the LB from a 2nd PS that the 2nd PS will carry the ~20W for the G3 upgrade??
thanks for listening - I am still working it - I may test load at the 120V supply of both my stockk CC and the PCC with the 6500 to see amp draw difference into the analog PS
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StuartBell
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Re: Power CC - power supply loading
« Reply #3 on: Oct 24th, 2002, 10:07am » |
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on Oct 24th, 2002, 8:55am, hobby wrote:Here's an update on loading:
G3 L2 upgrade card uses 20 - 30W dependent on which model, and this is 3.3V
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You'd better aim for a 10W 3.3v supply then. IMHO this suggests a separate supply rather than trying to take it off an existing rail, Takky-style.
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also interested in how the LB supports 3.3V supply, since it generates its own, is it a parrallel supply to external 3.3v connected, or does the LB 3.3 only support boot up & cache?
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Beware that it may be that 3.3v can appear on the 3.3v line to the l/b, even if your external source isn't working. I think that as the l/b produces 3.3v for limited internal use, and it's also got to accept 3.3v from external sources for higher current applicatons, and as the two supplies are commoned, the l/b 'supplies' 3.3v at a minimal maximum current to the 'outside'.
I think that my problems with getting a 3.3v supply working was that (i) when the l/b isn't installed, you can't check the 3.3v supply because it's not under load, but (ii) when the l/b is installed, its output on the 3.3v rail can mask the fact that the external 3.3v supply isn't working.
It wasn't until after many months of hair-tearing that I found out about x500 boards producing 3.3v on-board, and hence undermining my diagnostic efforts. <phew>
Stuart
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Stuart Bell,
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Colo(u)r Classic Forum.
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hobby
Member
Posts: 17
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Re: Power CC - power supply loading
« Reply #4 on: Oct 24th, 2002, 10:41am » |
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Very interesting, the LB produced 3.3v is something of a mystery then,
I have been able to dig up some apple tech info notes that confirm that the 603e (3W) and G3 (6W) CPUs are 3.3v
also the data ram on the cache is 3.3v, the tag ram is 5v
so the LB is producing enough 3.3v current for the CPU and the cache
what is interesting is that the "custom built" 3.3v regulator that takky describes and many of you have made, is fairly meaty in the area of heat dissipation - heatsink etc, I think the thing is rated at about 15W, the ones on ATX PS I've seen are around 7-10amps = 20-30W
if the 6500 LB is able to generate at least 3-5W, maybe more? it is doing this without a beefy regulator or heatsink?
I might be missing something regrading the CPU or cache power though, I will keep pondering......
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