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AuthorTopic: rapsberry pi  (Read 1236 times)

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Offline kickstart

rapsberry pi
« on: December 30, 2012, 08:04:12 PM »
Hi...

I have some questions about power supply of the raspberry pi, i going to use some of my micro-usb porwer supply, but which one?

A samsung one from a mp3 player, output: 5v 0,7a
Nokia ac-10e, output: 5v 1200ma
Another samsung from a tablet, output 5v 2a

Thanks and happy new year to all!
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Offline som99

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Re: rapsberry pi
« Reply #1 on: December 30, 2012, 08:12:38 PM »
If you plan to overclock and use the GPIO for anything then use the 2A one tho in most cases the 1,2A one will also be enough. Also if you plan on adding usb devices you want to use the bigger one but using external drives will most likely need a powered USB hub.

If you only plan to use it as it is with only a flashdrive and such the 0,7A one will do just fine (even moderate overclocking will survive on 0,7A)

If you do not use the 2A one for something else then use it, if you use a weaker one and you drain more then it can give the pi will shut off.

Happy new year to you also :)
« Last Edit: December 30, 2012, 08:21:52 PM by som99 »
 

Offline kickstart

Re: rapsberry pi
« Reply #2 on: December 30, 2012, 08:22:07 PM »
I dont know how to use it till i see the performance, dont know what OS is lighter or how emulators run in it (amstrad, c64, spectrum, mame). Need some cooler if is overcloked?

Thanks.
a1200 060
 

Offline bbond007

Re: rapsberry pi
« Reply #3 on: December 30, 2012, 08:35:00 PM »
Quote from: kickstart;720714
Hi...

I have some questions about power supply of the raspberry pi, i going to use some of my micro-usb porwer supply, but which one?

A samsung one from a mp3 player, output: 5v 0,7a
Nokia ac-10e, output: 5v 1200ma
Another samsung from a tablet, output 5v 2a

Thanks and happy new year to all!


I'm pretty sure that it makes no difference once you go over 1a... meaning that there is no real advantage to 2A. save it for the tablet.

I was experiencing some strange USB problems the other day and it tuned out to be that I had used a .75a PS that was maybe underperforming a little.

I had the RPI plugged into powered 8port hub. The hub was plugged into a mouse/kb and my iPhone. Everything was working fone except, until I started using the iPhone's 3G connection for internet. When I would start to DL something the phone would disconnect from USB. I thought it was really strange because the phone was plugged into that powered 8-port hub...
 

Offline som99

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Re: rapsberry pi
« Reply #4 on: December 30, 2012, 08:38:03 PM »
Quote from: kickstart;720717
I dont know how to use it till i see the performance, dont know what OS is lighter or how emulators run in it (amstrad, c64, spectrum, mame). Need some cooler if is overcloked?

Thanks.

Then go for the 1A one and your safe. Regarding overclocking,  if you want to stay on the safe side without risking the hardware you won't need a passive or active cooling solution, if you want to push it then you will need extra cooling, I myself have made a 2x2cm aluminum heatsink and mounted a 2x2cm fan on it taking power from the GPIO since I push it hard tho I overvolt the cpu quite a bit, I've found that if I use it caseless I won't need the fan but long runs in the case and the fan was needed. Some say that you won't need an active fan at 1GHz but I find it way to hot to feel safe using it for long periods in the case.

Normal overclocking = no cooling but you can always stick a small heatsink on there if you want to be extra safe.
« Last Edit: December 30, 2012, 08:46:10 PM by som99 »
 

Offline CritAnime

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Re: rapsberry pi
« Reply #5 on: January 01, 2013, 08:17:02 AM »
C64 emulation is still choppy even on 1ghz turbo mode. I think this is down to the code needing more optimisation for the specific arm type used on the pi. I haven't experimented with the memory split yet though. With a 512mb pi I might put the memory split upto 100mb for graphics. That might also help in the long run.

Also the power supply I got was from maplin and came as part of the kit I bought. It's a 2A max supply. However it will switch between 1A and 1.5A.

Offline gaula92

Re: rapsberry pi
« Reply #6 on: January 01, 2013, 12:29:02 PM »
Quote from: CritAnime;720847
C64 emulation is still choppy even on 1ghz turbo mode. I think this is down to the code needing more optimisation for the specific arm type used on the pi.

The problem right now with almost every piece of software in the Pi is libSDL. If you take any emulator or native game and use gdb with it, you'll see A LOT of time in erch running cycle (let's say from vsync to vsync) is spent in the SDL software blitting functions. In an X86 machine, libSDL provides asm code for mmx blitting, etc.
There's also the scaling problem: any game/emulator on SDL being stretched from low-res modes is eating almost every remaining CPU cycle per frame in software scaling.
That's lame.
I implemented a dispmanx backend for SDL (https://github.com/vanfanel/SDL12-kms-dispmanx) wich solves the scaling problem, but the blitting problem remains. GLES could be used somehow to do it, but I have yet to understand how :D
 

Offline CritAnime

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Re: rapsberry pi
« Reply #7 on: January 01, 2013, 10:58:18 PM »
Its thee c64 emulation I have had issues with specifically. When no sound is running I get a smooth framerate. However switch sound on and I get 5-11fps so I don't know if there is any issue with Alsa.

Offline kickstart

Re: rapsberry pi
« Reply #8 on: January 01, 2013, 11:11:50 PM »
8bit emulation dont work at 100%?, one of the main reasons to buy the raspberry pi is the emulation connected directly to a crt.
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