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I am planning to use my RPi as a basic desktop. I have a few questions

I am using the first model of the RPi

I am planning to connect a keyboard, a mouse, a bluetooth adapter, a WiFi adapter, and maybe a USB sound card

These are six items, and not including any Flash drives I may want to connect. And I do have a USB hub, although not powered. Here in India, the only reliable powered USB hubs are around $15 dollars. I have ordered a 7 port USB hub, hoping it's powered, but I'm not too sure, and I might return it.

Will giving more than 1Amp of power to the RPi allow me to attach a USB hub to another hub, without ruining the Pi?

Also, is it safe to overclock an encased RPi to the maximum preset? I'm using an official green RPI case with light indicators. Will a USB fan help?

Also, what memory split(of 256MB) would be good?

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The original A/B models have some problems with the USB ports and power.

For starters, they won't deliver much more than 150 mA each, and the USB 2.0 standard is 500 mA. This means certain things such as external drives will not work.

Generally, keyboards, mice, wifi adapters, and bluetooth adapters are okay. However, I believe many wifi adapters will be close to this boundary.

Further, inserting a device which requires close to the threshold (such as a wifi adapter) will cause a current surge and corresponding voltage drop, which browns the pi out: I.e., it will reboot instantly. That means these devices must be attached before you power up, and if removed, cannot be re-inserted.

To summarize, you almost certainly need a powered hub to try and do what you want.

attach a USB hub to another hub, without ruining the Pi

Considering one port is going to have this sub-standard limit, chaining hubs on it will be completely pointless. Any amount of things you want to attach requiring more than one hub will simply be too much -- unless, again, they have their own power supply.

is it safe to overclock an encased RPi to the maximum preset?

The major risk of overclocking is due to overheating, so you want to pay attention to your temperature (vcgencmd measure_temp) when the pi is working hard, which will be often but not constantly in a desktop context. Make sure to install a CPU monitor to watch this so you know when to wait for something to finish, and if usage remains at 100% for a long time, check the core temperature. If it is exceeds 85 °C you are in trouble, and if it even gets close to that (say < 70) reduce your overclock settings. You are slowly ruining the processor.

The linux kernel on Raspbian defaults to a scaling governor, meaning the CPU frequency can be adjusted on the fly as needed. This means you can set something like:

arm_freq=900
arm_freq_min=600

In config.txt and the governor will use 600 Mhz when idle and ramp up to 900 Mhz when busy. See the official docs about overclocking for more on this.

Normal operating temp for a pi is 35-45 °C, which may vary with a the ambient temperature. I've used scaling overclock settings like the above on a B, and when running at 900 Mhz, 100% CPU usage, even after 10-15 minutes in a ~25 °C room it does not reach 50 °C. There are monitors that will show both CPU usage and core temp (my preference is gkrellm) which is useful for testing this.

Beware that part of the issue with overclocking is that chips that are supposed to be exactly the same may actually differ slightly due to factors in manufacturing, which is why some will perform better than others.

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The Raspberry Pi will draw whatever current it requires, if you look at the recommended power for it, its 1.2A 5V. I personally suggest getting an official Raspberry Pi power supply but a high quality phone or tablet charger which meets the power requirements is fine. So a 1A power supply might just cut it, but really you need 1.2A.

I'm assuming your using an original model B Pi, these only have 2 USB ports, so a USB hub is a must. It must also be powered because there is no way the Pi can power six USB devices by itself.

One way to cut down on the number of USB devices connected to it is to first use a combined Bluetooth/Wi-Fi adapter, or a Bluetooth adapter and use an Ethernet connection. You can also run the Pi headless which means you control the Pi over a network from a computer, this negates the need for a keyboard and mouse to be connected to the Pi. If your interested in that look into PuTTy and VNC Viewer.

It is safe to overclock to the Pi, in your case I think it might be necessary given your using an original Pi. This can be done through the raspi-config.txt file, I believe there is also a turbo mode which overclocks the CPU when necessary. Manually overclocking the Pi will void the warranty, you have been warned. The Pi is designed to not need active cooling and will only start to thermal throttle at 85°C. A fan and heatsinks are not a requirement, although they can shave 15°C off the CPU temps.

With regards to splitting the memory it depends on if your doing more GPU or CPU bound tasks. I'm sure there is a setting which means the Pi will split the memory automatically. However the memory split can be changed in the config.txt file.

I suggest if possible looking at getting a Pi 3 which has 4 USB ports, Wi-Fi and bluetooth built in. It is also around ten times as powerful as the Pi 1.

  • Thanks so much! Just a small thing, I am using the Pi A, so it only has one USB port(I think). Is it safe to use a 2.1 Amp power supply for the Pi? Also, I haven't known about overclocking from a text file, but by using the command,'raspi-config', you can overclock, to some presets. I'm just scared that it might over heat(or shutdown while doing a task). – PiAhoy Apr 15 '16 at 17:20
  • @PiAhoy Yes, that's perfectly fine. Better actually :) – Android Dev Apr 15 '16 at 17:24

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