dics
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Re: Ethernet chip gets raging hot

Sun May 27, 2012 8:03 am

There is no USB traffic on my RPi.
The board stays up and I am setting it up using SSH.
Last night I tried to make the test again and this time no kernel panic message but the ethernet unconfigured itself after transferring ~500MB.
It might be something wrong with the ethernet drivers and not a temperature issue

milhouse
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Re: Ethernet chip gets raging hot

Sun May 27, 2012 10:19 am

Watching iPlayer (BBC HD) in Raspbmc and the SoC and USB/LAN chips are [both too hot to touch for more than 5 seconds... is this normal/expected? Any longer than 5 seconds and it really is too uncomfortable (ie. painful) to keep a finger pressed on the surface of either IC (unfortunately I don't have a temperature sensor to obtain accurate figures - the best I can do is my kitchen thermometer which suggests the temp is about 90F/32.2C). Despite the temperatures, the device appears stable.

The Pi is powered with a 2A/5V HP Touchpad PSU.

Connected to the Pi are a USB keyboard, USB IR MCE remote control sensor, ethernet cable and HDMI.

"1213" is silk screened on the board next to the microUSB socket, purchased from Farnell.

Joe Schmoe
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Re: Ethernet chip gets raging hot

Sun May 27, 2012 10:30 am

dics wrote:There is no USB traffic on my RPi.
The board stays up and I am setting it up using SSH.
Last night I tried to make the test again and this time no kernel panic message but the ethernet unconfigured itself after transferring ~500MB.
It might be something wrong with the ethernet drivers and not a temperature issue
On the Pi (model B), ethernet *is* USB. So, there is USB traffic.
And some folks need to stop being fanboys and see the forest behind the trees.

(One of the best lines I've seen on this board lately)

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mahjongg
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Re: Ethernet chip gets raging hot

Sun May 27, 2012 12:55 pm

milhouse wrote:Watching iPlayer (BBC HD) in Raspbmc and the SoC and USB/LAN chips are [both too hot to touch for more than 5 seconds... is this normal/expected? Any longer than 5 seconds and it really is too uncomfortable (ie. painful) to keep a finger pressed on the surface of either IC
Well, its just that you -can- put a finger on a chip in the raspberry PI, if you would open an average PC, and attempted to touch some of the chips you would soon realise that yes, it is normal/expected for chips to "get too hot to comfortable touch for seconds in a row", in fact you would probably got blisters in fractions of a second.
A chip that is just 38 degrees may be painful to touch, but that says nothing! maybe if it gets up to twice that (76 degrees) its time to start to worry.
Chips are not designed to be comfortable to touch with human hands, they are designed to not exceed limits laid down by the physics of the materials involved.

The educational (kids) release will have a case to prevent kids to put their fingers on such chips, or to poke around with a pair of scissors.

milhouse
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Re: Ethernet chip gets raging hot

Sun May 27, 2012 1:14 pm

mahjongg wrote: Well, its just that you -can- put a finger on a chip in the raspberry PI, if you would open an average PC, and attempted to touch some of the chips you would soon realise that yes, it is normal/expected for chips to "get too hot to comfortable touch for seconds in a row", in fact you would probably got blisters in fractions of a second.
I really don't see the relevance of comparing the Pi and its ARM SoC with a PC to this discussion - it's apples and oranges.

The ARM SoC is not an x86 CPU, it's a completely different level of power consumption, and by all accounts the Pi is supposed to run "cool" - what I'm asking is whether the temperature that I and others are experiencing is expected of the Raspberry Pi (ie. even though it's blisteringly hot, yes this is still considered "cool" and within limits). Or is there an issue?

This same SoC (or one very much like it) can be found in a Nokia N8 smartphone and I'd be extremely worried if I were to run the N8 at full bore with the SoC achieving temperatures similar to those I'm experiencing on an open board (obviously it doesn't have any temperature issues so something is different).

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johnbeetem
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Re: Ethernet chip gets raging hot

Sun May 27, 2012 3:01 pm

mmcv2008 wrote:I did buy now some heatsinks (http://www.zerotherm.net/eng/product/ZH100.asp on amazon for 6.90€ incl. shipping), normally for VGA boards, but two of them fit exactlly onto the CPU and the LAN chip and looking nice also.
Thank you for posting this and the pretty picture. I am personally very cautious about hot components as they can really shorten the life of a product, especially if you thermal cycle it. I detest BGAs. Gull wings rule! They also flex when thermal cycled, instead of cracking like BGA balls.

I have a pretty blue heat sink on my BeagleBoard SoC. BeagleBoard's hardware designer Gerald Coley thought it was silly when he saw it.

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Montala
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Re: Ethernet chip gets raging hot

Sun May 27, 2012 5:06 pm

Reading through this thread makes me wonder if this is a real problem, or not, and whether it is worthwhile considering the fitting of small heat-sinks on our boards, as shown in an earlier picture.

Perhaps one of the Foundation members, or designers would care to comment?

milhouse
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Re: Ethernet chip gets raging hot

Sun May 27, 2012 5:19 pm

Montala wrote: Perhaps one of the Foundation members, or designers would care to comment?
That's all I'm looking for. Gert earlier in the thread gives the impression that the temperatures being observed are higher than expected ("so hot") and thus presumably not normal, in which case clarification of these temperatures - whether they are high, or not - would be most welcome. If the temperatures are within range then fine, I'm no longer concerned - but if not, then future batches need to be addressed (and as long as mine continues to function normally I'm happy to hold on to it).

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Re: Ethernet chip gets raging hot

Mon May 28, 2012 12:51 am

milhouse wrote:I really don't see the relevance of comparing the Pi and its ARM SoC with a PC to this discussion - it's apples and oranges.
It strange that you do not see that if chips in a PC can get hot without it being a problem, its not technically a problem when chips get hot.
Yes the R-PI is very low power, and no that its using "ARM technology" is irrelevant, the HUB/Ethernet chip isn't ARM technology, or specifically low power. Its very tiny, consuming almost a watt, and only having the copper area of a very tiny (credit card size) board to draw away heat, so it getting a bit warm, no big deal! Ethernet Chips, (and USB chips) transfer signals of relatively big amplitudes (several volts) into low resistance loads, (so sending lots of current), this takes energy, so by nature USB and Ethernet (PHY) chips consume a bit of energy, that is normal and cannot be altered.

having heatsinks on these chips is IMHO ridiculous! They were designed for their purpose, to be used without the need for a heatsink.
Unless there is some defect in the HUB/Ethernet chip, there is no reason to put a heatsink on it, and if it is defective, then its defective, and shouldn't be used (with or without a heatsink) .

All I'm otherwise saying is that using your finger as an instrument to determine that a chip is "abnormally hot" is simply using the wrong tool, as that way isn't the way to test for an "abnormal hot" component, you need at least an infrared thermometer, and knowledge about the specifications of the component, and calculations on the heat transfer of the chip to determine such a thing. Only if the chips starts to fail, smells funny, emits the "magic smoke", or melts from the board your senses are suitable to tell you something is wrong!

That isn't to say that chips cannot fail internally, or get too high a voltage, and thus overheat. If you can compare two identical systems under identical conditions, and one behaves extremely differently, in dissipating energy, you can make an "educated guess" that there is something wrong with that system. Not when you do not know the device or what its normal behaviour is.

The original post mentioned the system failed after some time, that would be an indication of a problem, not that you cannot touch the chip for several seconds because it then feels "uncomfortable".

Harrkev
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 2:54 am

Just for the record, mine is hot too (from RS). I can keep my finger on there for about five seconds before too much pain.

There is almost NO network traffic, and the only thing hooked up to USB is a single Logitech nano-receiver for a wireless keyboard/mouse combo (note that the wireless receiver itself is quite cool).

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Re: Ethernet chip gets raging hot

Tue May 29, 2012 7:00 am

I am intrigued how a finger is a good measure of a chip working in-spec of the temperature range it can handle?
The machine is just that.. keep your fingers off it.. it's electrical.. would you put you fingers into the back of your TV if the back was off?
Fingers conduct, so can short things out.. plus there is grease on them, which isn't good to get all over electrical devices.
I know this isn't a high voltage device to risk to life etc. is minimal, but still good practice to keep off when plugged in.
I used an infra-red thermometer to check the temp. which is non-invasive.

simonbr
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 9:55 am

spurious wrote:I am intrigued how a finger is a good measure of a chip working in-spec of the temperature range it can handle?
The machine is just that.. keep your fingers off it.. it's electrical.. would you put you fingers into the back of your TV if the back was off?
Fingers conduct, so can short things out.. plus there is grease on them, which isn't good to get all over electrical devices.
I know this isn't a high voltage device to risk to life etc. is minimal, but still good practice to keep off when plugged in.
I used an infra-red thermometer to check the temp. which is non-invasive.
Did you take into account the FOV of the thermometer?

nertia
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 12:53 pm

I am also slightly concerned by the temperature of the USB/ethernet chip. Within 20 minutes of booting the Debian image the ethernet port becomes distinctly warm because of its proximity to the USB chip. I have measured the temperature by holding the thermocouple on my multimeter directly on the chip's surface:

Conditions during temperature reading
~6% CPU usage
~20MB RAM usage
No X session
SSH connection over ethernet port
PI unboxed open to free air cooling
6 days uptime

Temperature Reading
Ambient air temp :23 degrees Celsius
Chip surface temp:47/48 degrees Celsius
Results after obtained 30 seconds contact with chip surface and remaining more or less constant for at least 2 minutes.

My setup
Raspberry Pi model B (RS components May 2012)
HTC DesireHD 1000ma charger
Rapoo E9080 wireless USB keyboard

Code: Select all

[email protected]:~$ lsusb
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. 
Bus 001 Device 004: ID 24ae:1000  
Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Ethernet connected

Code: Select all

[email protected]:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr b8:27:eb:e1:a3:42  
          inet addr:192.168.2.19  Bcast:192.168.2.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1488  Metric:1
          RX packets:62189 errors:0 dropped:0 overruns:0 frame:0
          TX packets:37804 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:8337684 (7.9 MiB)  TX bytes:35274530 (33.6 MiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:13930 errors:0 dropped:0 overruns:0 frame:0
          TX packets:13930 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:34562280 (32.9 MiB)  TX bytes:34562280 (32.9 MiB)
dmesg output:

Code: Select all

[email protected]:~$ dmesg
Linux version 3.1.9+ ([email protected]) (gcc version 4.5.1 (Broadcom-2708) ) #90 Wed Apr 18 18:23:05 BST 2012
CPU: ARMv6-compatible processor [410fb767] revision 7 (ARMv7), cr=00c5387d
CPU: VIPT nonaliasing data cache, VIPT nonaliasing instruction cache
Machine: BCM2708
Memory policy: ECC disabled, Data cache writeback
On node 0 totalpages: 49152
free_area_init_node: node 0, pgdat c03b5660, node_mem_map c0402000
  Normal zone: 384 pages used for memmap
  Normal zone: 0 pages reserved
  Normal zone: 48768 pages, LIFO batch:15
pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
pcpu-alloc: [0] 0 
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 48768
Kernel command line: dma.dmachans=0x3c bcm2708_fb.fbwidth=656 bcm2708_fb.fbheight=416 bcm2708.boardrev=0x2 bcm2708.serial=0xb6e1a342 smsc95xx.macaddr=B8:27:EB:E1:A3:42 dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait
PID hash table entries: 1024 (order: 0, 4096 bytes)
Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
Memory: 192MB = 192MB total
Memory: 190720k/190720k available, 5888k reserved, 0K highmem
Virtual kernel memory layout:
    vector  : 0xffff0000 - 0xffff1000   (   4 kB)
    fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB)
    DMA     : 0xffc00000 - 0xffe00000   (   2 MB)
    vmalloc : 0xcc800000 - 0xd8000000   ( 184 MB)
    lowmem  : 0xc0000000 - 0xcc000000   ( 192 MB)
    modules : 0xbf000000 - 0xc0000000   (  16 MB)
      .text : 0xc0008000 - 0xc037b000   (3532 kB)
      .init : 0xc037b000 - 0xc0398000   ( 116 kB)
      .data : 0xc0398000 - 0xc03b5ce0   ( 120 kB)
       .bss : 0xc03b5d04 - 0xc0401198   ( 302 kB)
NR_IRQS:85
timer_set_mode: unhandled mode:1
timer_set_mode: unhandled mode:3
Console: colour dummy device 80x30
console [tty1] enabled
Calibrating delay loop... 697.95 BogoMIPS (lpj=3489792)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
devtmpfs: initialized
NET: Registered protocol family 16
vc-mem: mm_vc_mem_phys_addr = 0x00000000
vc-mem: mm_vc_mem_size      = 0x10000000 (256 MiB)
mailbox: Broadcom VideoCore Mailbox driver
bcm2708_vcio: mailbox at f200b880
bcm_power: Broadcom power driver
bcm_power_open() -> 0
bcm_power_request(0, 8)
bcm_mailbox_read -> 00000080, 0
bcm_power_request -> 0
Serial: AMBA PL011 UART driver
dev:f1: ttyAMA0 at MMIO 0x20201000 (irq = 83) is a PL011 rev3
console [ttyAMA0] enabled
bio: create slab <bio-0> at 0
SCSI subsystem initialized
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
Switching to clocksource stc
FS-Cache: Loaded
CacheFiles: Loaded
Switched to NOHz mode on CPU #0
NET: Registered protocol family 2
IP route cache hash table entries: 2048 (order: 1, 8192 bytes)
TCP established hash table entries: 8192 (order: 4, 65536 bytes)
TCP bind hash table entries: 8192 (order: 3, 32768 bytes)
TCP: Hash tables configured (established 8192 bind 8192)
TCP reno registered
UDP hash table entries: 256 (order: 0, 4096 bytes)
UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
NET: Registered protocol family 1
RPC: Registered named UNIX socket transport module.
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transport module.
bcm2708_dma: DMA manager at cc808000
bcm2708_gpio: bcm2708_gpio_probe c039dd88
vc-mem: Videocore memory driver
VFS: Disk quotas dquot_6.5.2
Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
FS-Cache: Netfs 'nfs' registered for caching
msgmni has been set to 372
io scheduler noop registered
io scheduler deadline registered
io scheduler cfq registered (default)
BCM2708FB: registering framebuffer (656, 416)
bcm2708_fb_set_par info(cb888000) 656x416 (656x416), 0, 16
BCM2708FB: start = cc900000,4d384000 width=656, height=416, bpp=16, pitch=1312 size=545792 success=0
Console: switching to colour frame buffer device 82x26
BCM2708FB: register framebuffer (0)
brd: module loaded
loop: module loaded
vcos: [1]: vchiq_init_state: slot_zero = 0xffd80000, is_master = 0
vcos: [1]: vchiq_init_state: called
vcos: [1]: vchiq: initialised - version 2 (min 2), device 253.0
usbcore: registered new interface driver smsc95xx
cdc_ncm: 04-Aug-2011
usbcore: registered new interface driver cdc_ncm
dwc_otg: version 2.90b 6-MAY-2010 (platform bus)
Core Release: 2.80a
Setting default values for core params
Finished setting default values for core params
cc840008 -> 1
Using Buffer DMA mode
Periodic Transfer Interrupt Enhancement - disabled
Multiprocessor Interrupt Enhancement - disabled
Dedicated Tx FIFOs mode
dwc_otg bcm2708_usb: DWC OTG Controller
dwc_otg bcm2708_usb: new USB bus registered, assigned bus number 1
dwc_otg bcm2708_usb: irq 75, io mem 0x00000000
Init: Port Power? op_state=1
Init: Power Port (0)
usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb1: Product: DWC OTG Controller
usb usb1: Manufacturer: Linux 3.1.9+ dwc_otg_hcd
usb usb1: SerialNumber: bcm2708_usb
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 1 port detected
Module dwc_common_port init
Initializing USB Mass Storage driver...
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
usbcore: registered new interface driver libusual
mousedev: PS/2 mouse device common for all mice
cpuidle: using governor ladder
cpuidle: using governor menu
sdhci: Secure Digital Host Controller Interface driver
sdhci: Copyright(c) Pierre Ossman
bcm_power_open() -> 1
Registered led device: mmc0::
mmc0: SDHCI controller on BCM2708_Arasan [platform] using platform's DMA
mmc0: BCM2708 SDHC host at 0x20300000 DMA 2 IRQ 77
sdhci-pltfm: SDHCI platform and OF driver helper
Registered led device: led0
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
TCP cubic registered
Initializing XFRM netlink socket
NET: Registered protocol family 17
Registering the dns_resolver key type
VFP support v0.3: implementor 41 architecture 1 part 20 variant b rev 5
Waiting for root device /dev/mmcblk0p2...
mmc0: problem reading SD Status register.
mmc0: new SDHC card at address 0002
mmcblk0: mmc0:0002 00000 3.70 GiB 
 mmcblk0: p1 p2 p3
usb 1-1: new high speed USB device number 2 using dwc_otg
EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null)
VFS: Mounted root (ext4 filesystem) on device 179:2.
Freeing init memory: 116K
usb 1-1: New USB device found, idVendor=0424, idProduct=9512
usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
hub 1-1:1.0: USB hub found
hub 1-1:1.0: 3 ports detected
usb 1-1.1: new high speed USB device number 3 using dwc_otg
usb 1-1.1: New USB device found, idVendor=0424, idProduct=ec00
usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
smsc95xx v1.0.4
smsc95xx 1-1.1:1.0: eth0: register 'smsc95xx' at usb-bcm2708_usb-1.1, smsc95xx USB 2.0 Ethernet, b8:27:eb:e1:a3:42
usb 1-1.2: new full speed USB device number 4 using dwc_otg
usb 1-1.2: New USB device found, idVendor=24ae, idProduct=1000
usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 1-1.2: Product: Rapoo 2.4G Wireless Touch Desktop 
usb 1-1.2: Manufacturer: MOSART Semi.
input: MOSART Semi. Rapoo 2.4G Wireless Touch Desktop  as /devices/platform/bcm2708_usb/usb1/1-1/1-1.2/1-1.2:1.0/input/input0
generic-usb 0003:24AE:1000.0001: input: USB HID v1.10 Keyboard [MOSART Semi. Rapoo 2.4G Wireless Touch Desktop ] on usb-bcm2708_usb-1.2/input0
input: MOSART Semi. Rapoo 2.4G Wireless Touch Desktop  as /devices/platform/bcm2708_usb/usb1/1-1/1-1.2/1-1.2:1.1/input/input1
generic-usb 0003:24AE:1000.0002: input,hiddev0: USB HID v1.10 Mouse [MOSART Semi. Rapoo 2.4G Wireless Touch Desktop ] on usb-bcm2708_usb-1.2/input1
EXT4-fs (mmcblk0p2): re-mounted. Opts: (null)
fuse init (API version 7.17)
smsc95xx 1-1.1:1.0: eth0: link up, 100Mbps, full-duplex, lpa 0xC5E1
sshd (739): /proc/739/oom_adj is deprecated, please use /proc/739/oom_score_adj instead.
bcm2708_fb_check_var info(cb888000) 656x416 (656x416), 545792, 16
bcm2708_fb_check_var var(cac4fcfc) 656x416 (656x416), 16, 272896
bcm2708_fb_set_par info(cb888000) 656x416 (656x416), 545792, 16
BCM2708FB: start = cca00000,4d384000 width=656, height=416, bpp=16, pitch=1312 size=545792 success=0
My guess is that the wireless USB keyboard is drawing a lot of power. I am not massively concerned but would like to know that this configuration will not damage my PI or reduce its lifespan.

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rurwin
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 1:24 pm

nertia wrote: Ambient air temp :23 degrees Celsius
Chip surface temp:47/48 degrees Celsius
It will be a few degrees above that, because the thermal resistance between the chip and the thermister will have been quite high. That is at least twice the power disipation that other people are seeing, if we can trust them to use their IR thermometers, and it matches the OP's description of "too hot to touch for long".
20C = Room Temperature
40C = Hot Bath
50C = Too hot to touch for long
60C = Too hot to touch
70C = Painful to touch
My guess is that the wireless USB keyboard is drawing a lot of power.
No, because the power for the keyboard does not go through the chip; it is fed direct from the power supply.

Can we hear from other people that their chip is much cooler than a Hot Bath? Just to check those IR thermometers are reading right?

milhouse
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 1:38 pm

spurious wrote:I am intrigued how a finger is a good measure of a chip working in-spec of the temperature range it can handle?
It's not, and I doubt anyone is claiming that it is - just that if the chips are meant to be "cool" then my finger can certainly determine that they are anything but cool! Of course "cool" is a pretty vague definition of the working temperature, so clarification of what is to be expected would be most welcome.

Since this is a new design I think it's valid to question whether the temperatures being experienced by early adopters - even when determined with a human digit "it's bl**dy hot!" - are to be expected or not. Certainly the indication from Gert is that some devices may be running hotter than expected, which could indicate a problem somewhere in the design (or manufacture).

simonbr
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 2:01 pm

rurwin wrote:if we can trust them to use their IR thermometers
And if we can trust them to use their IR thermometers correctly... these measure the temperature averaged over a circular area with a size that depends on measuring distance and FOV.

This chip is so small that it may be difficult to accurately get its temperature without averaging over a larger (cooler) area around it.

Best regards
Simon

spurious
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 4:05 pm

Yes FOV taken into account..
Just to satistfy the weird people who think fingers are thermomters I can held my finger on the new board I got from Farnell.
IR thememeter
Ambient 25.1C
CPU 48.9C
Eth 50.8

Finger touch:
Ambient.. air them seems warm
CPU.. Warmer than air but can leave finger on.. not sure why you would want to..
Eth counted to 5 before finger was uncomfy... why am I doing this weirdness

USE A THERMOMETER!!!! :lol:

if I repeated the steps after entering the house from cold outside this would all seem so much hotter to touch, so fingers are not a reliable method.


and yes it's too hot to leave your finger on, but so what.. it's working and probably well within the spec of what it can handle.

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Re: Ethernet chip gets raging hot

Tue May 29, 2012 5:10 pm

How hot a surface feels has actually less to do with its temperature, and more with how conductive to heat the surface material is. Anything warmer than 37 degrees will try to emit heat to your finger, the easier it is to transfer this heat, the more intense the feeling of hot/pain. So touching a piece of metal that is 39 degrees, will be more painful than touching say Styrofoam that is heated to 49 degrees.

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rurwin
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 5:38 pm

Granted that finger are in no way accurate, but neither are many other ways to measure temperature, which is difficult to measure due to the vagueries of thermal resistance, emissivity and FOV. However a chip that is under 37C is unlikely to feel as hot as the OP reported, yet at least two people reported that it was well under that temperature.

50C, ambient +25C, is a reasonable temperature for an IC. It is even in the ballpark for ICs dissipating 750mW. There would be no concern unless it was significantly hotter than the majority of other boards. I don't now see evidence that it is.

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bigsi111
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 7:39 pm

I've just tried the finger test and got to 7 seconds and I have asbestos fingers. I also tried childs' in ear monitor which just say very hi, so above 40c.

I'd guess there's a heat problem, so I'm getting heat sinks as they look bloody cool regardless of whether you need them or not!

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jbeale
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 8:50 pm

rurwin wrote:... vagaries of thermal resistance, emissivity and FOV...
My understanding is that almost all IC chip plastic packages have an emissivity very near 0.98 so an IR thermometer reading of the chip surface temperature will be fairly accurate, so long as its field of view is smaller than the package in question.

Just for fun here is a thermal-IR photo of an Arduino I took some time ago. The 5V regulator showing a red area is about 32 C, while the smudge at the center of the DIP processor shows the ATmega328 chip is just barely above the 22 C ambient. Except for the small LED and its load resistor, the other small dark spots are not hot spots but reflections off (low-emissivity) metal surfaces (pins, solder, electrolytic cap cans) of heat sources outside the frame.

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mahjongg
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 9:22 pm

bigsi111 wrote:I've just tried the finger test and got to 7 seconds and I have asbestos fingers. I also tried childs' in ear monitor which just say very hi, so above 40c.

I'd guess there's a heat problem, so I'm getting heat sinks as they look bloody cool regardless of whether you need them or not!
I'd guess there's a heat problem"? Where is there "a heat problem"?
Again, there is NO HEAT PROBLEM, just because your finger indicates heat, and 40 degrees is certainly not a problem.

The LAN9512 normally uses only about the energy of a flashlight bulb, the only reason it gets somewhat warm is because its so tiny, but its designed for that, so there is nothing special going on with it.

If it really "raging hot", and is failing, then that is a different issue, but nothing except the first post indicates that what is observed is problematic.

If you put a heatsink on it because it "looks cool" then sorry, but that is just silliness. Everyone has its own taste I guess, but I fear that it won't emit so much heat, as "emitting" the wrong message.
Last edited by mahjongg on Tue May 29, 2012 9:26 pm, edited 1 time in total.

simonbr
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Re: Ethernet chip gets raging hot

Tue May 29, 2012 9:23 pm

spurious wrote:Yes FOV taken into account..
Just to satistfy the weird people who think fingers are thermomters I can held my finger on the new board I got from Farnell.
IR thememeter
Ambient 25.1C
CPU 48.9C
Eth 50.8
These values are quite different from what you reported earlier...

Best regards
Simon

milhouse
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Re: Ethernet chip gets raging hot

Wed May 30, 2012 5:06 am

mahjongg wrote: I'd guess there's a heat problem"? Where is there "a heat problem"?
Again, there is NO HEAT PROBLEM, just because your finger indicates heat, and 40 degrees is certainly not a problem.
There IS a heat problem if the chip is meant to be running at or below 30C.

Unless we know what is a "normal" temperature nobody can claim there is or there is not a problem. So far, we're only questioning if there might be a problem, considering that the main ICs seem to be running at a higher temperature than might be expected ("cool", whatever temperature that is), and we're not getting any answers from people that know what they're talking about (ie. people from the Foundation).

So unless you KNOW what temperatures these chips are expected to achieve in the Raspberry Pi, you're simply not qualified to say if there is or is not a heat problem.
mahjongg wrote:If it really "raging hot", and is failing, then that is a different issue,
Do you know if the current temperatures are likely to lead to a shortened lifetime for the device? It might be working right now, but it might only last 6 months or a year due to the excessive heat or whatever is causing the excessive heat (assuming there is any excessive heat at all).

Again, do you know what the normal operating temperature of the various ICs is meant to be? If not, I'll wait for a suitably qualified individual from the Foundation to chime in.

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bigsi111
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Re: Ethernet chip gets raging hot

Wed May 30, 2012 7:27 am

mahjongg wrote:
bigsi111 wrote:I've just tried the finger test and got to 7 seconds and I have asbestos fingers. I also tried childs' in ear monitor which just say very hi, so above 40c.

I'd guess there's a heat problem, so I'm getting heat sinks as they look bloody cool regardless of whether you need them or not!
I'd guess there's a heat problem"? Where is there "a heat problem"?
Again, there is NO HEAT PROBLEM, just because your finger indicates heat, and 40 degrees is certainly not a problem.

The LAN9512 normally uses only about the energy of a flashlight bulb, the only reason it gets somewhat warm is because its so tiny, but its designed for that, so there is nothing special going on with it.

If it really "raging hot", and is failing, then that is a different issue, but nothing except the first post indicates that what is observed is problematic.

If you put a heatsink on it because it "looks cool" then sorry, but that is just silliness. Everyone has its own taste I guess, but I fear that it won't emit so much heat, as "emitting" the wrong message.
As Millhouse says, if the chips is ment to run at circa 30c and it's at circa 40c, this may indicate a slight problem. Personally, I'm not bothered as at £25 for a Raspi is eff all to me, I spend more on chewing gum. The heatsink is tongue in cheek, although I do think it would look cool :lol: .

However, I was surprised at how much heat was being generated for the minimal load and whilst I'm happy to concede that I am probably wrong, the purpose of the Development Board is to iron out kinks and this could be a problem and does warrant some form of investigation.

Personally, I doubt there's a problem and we're all being silly.

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