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by jdb
Fri Apr 12, 2019 3:32 pm
Forum: Off topic discussion
Topic: I know this sounds like something from a Spy novel or makes me sound a like a crazy person but...
Replies: 26
Views: 640

Re: I know this sounds like something from a Spy novel or makes me sound a like a crazy person but...

If you want to get even more paranoid, note that every reasonably complex ASIC has silicon debug capable of reading out the entire state of the chip (for production test). https://hal-lirmm.ccsd.cnrs.fr/lirmm-00599690/document It's a potential attack vector for e.g. reading out your AES key but if y...
by jdb
Wed Apr 10, 2019 12:03 pm
Forum: Compute Module
Topic: I got thermal paste on my board
Replies: 7
Views: 220

Re: I got thermal paste on my board

Denatured alcohol is *not* isopropanol/isopropyl alcohol. In the UK at least, it's ethanol mixed with methanol, a far more aggressive solvent than isopropyl alcohol. Isopropyl alcohol is generally safe to use on PCBs to clean off gunk.
by jdb
Tue Apr 02, 2019 6:53 pm
Forum: Advanced users
Topic: Voltage reduction under thermal throttling
Replies: 7
Views: 286

Re: Voltage reduction under thermal throttling

There are three voltage/frequency setpoints for the 3B+ 1.2V @ 600MHz - when idle or throttled due to 5V undervoltage or due to exceeding the 85C temp limit "turbo" volts @ 1200MHz - when the temperature is above the soft temp limit and below the 85C temp limit. ARM frequency gets progressively ramp...
by jdb
Sat Mar 30, 2019 12:05 am
Forum: The MagPi
Topic: Issue 80 : Pi FM Transmitter
Replies: 7
Views: 577

Re: Issue 80 : Pi FM Transmitter

Thanks for bringing this to our attention.
by jdb
Fri Mar 29, 2019 7:29 pm
Forum: General discussion
Topic: Pi 4 questions
Replies: 166
Views: 6571

Re: Pi 4 questions

Core memory came back for Arduino chips a few years ago http://corememoryshield.com it’s not a bad price either £30 approx for 32 bits of memory. So so tempting :lol: Given modern ADC resolutions and speed, I wonder if you can't store more than 1 bit per ferrite. The principle of core memory relies...
by jdb
Fri Mar 29, 2019 12:43 pm
Forum: General discussion
Topic: Pi 4 questions
Replies: 166
Views: 6571

Re: Pi 4 questions

The problem with going for even smaller and smaller processes is that the smaller ones are REALLY EXPENSIVE. You will have noted that the prime selling point of the Pi is cost performance ratio. So we really are not interested in using the latesst technology, simply because its too expensive. So wh...
by jdb
Thu Mar 28, 2019 7:34 pm
Forum: General discussion
Topic: Pi 4 questions
Replies: 166
Views: 6571

Re: Pi 4 questions

I come here, I feel old. I visit the in-laws (91 & 92), I feel young. She complains about just about everything, so I tell her she's still got the Queen's telegram to look forward to. I doubt Charles will still be doing telegrams by the time I'm due for one, but I tell myself at least I've got the ...
by jdb
Thu Mar 28, 2019 4:33 pm
Forum: General discussion
Topic: Pi 4 questions
Replies: 166
Views: 6571

Re: Pi 4 questions

jbudd wrote:
Thu Mar 28, 2019 1:16 pm
Pushing slightly at the door marked "Secret" jamesh, do you have a working prototype on your desk yet?
no
by jdb
Fri Mar 22, 2019 9:21 pm
Forum: Automation, sensing and robotics
Topic: electric dog collar based on radio waves
Replies: 13
Views: 324

Re: electric dog collar based on radio waves

Thank You guys for all the help , I'm almost finished the normal fence to them2400metres squares to give them freedom , but if You are not up to make my idea on raspberry IT gave me a brighter look on this problem. Thanks, If somebody Has some idea please do not hesitate Do not use Raspberry Pis to...
by jdb
Fri Mar 22, 2019 4:23 pm
Forum: General discussion
Topic: Sterilization of Pi
Replies: 27
Views: 1111

Re: Sterilization of Pi

Never mind the stored charge (there won't be any after >10 seconds of power-off), what gas is being used? There are plastics/epoxies used in component encapsulation that may not play at all well with aggressive solvents.
by jdb
Mon Mar 04, 2019 1:28 pm
Forum: Off topic discussion
Topic: Is ARM doomed?
Replies: 298
Views: 11912

Re: Is ARM doomed?

In what way can the ARM be better implemented? What techniques would that improvement use that cannot also be used in a RISC V design? Ok I will bite and answer. The techniques would be the same for both ISA's to reach ideal performance of the ISA. The difference is that a single instruction (howev...
by jdb
Fri Feb 22, 2019 10:31 pm
Forum: General discussion
Topic: Why must the raspberrypi be so proprietary?
Replies: 44
Views: 1626

Re: Why must the raspberrypi be so proprietary?

LTolledo wrote:
Fri Feb 22, 2019 7:16 pm
I doubt the OP will be coming back to join the discussions here.....
Correct.
It's been 24 hours and OP hasn't replied to a thread that's got dozens of replies (including from RPTL employees)

Locked, trollbait detected.
by jdb
Fri Feb 22, 2019 1:09 pm
Forum: Advanced users
Topic: Raspberry Pi SRAM
Replies: 21
Views: 1251

Re: Raspberry Pi SRAM

If we're looking for hardware differentiability, then there's a set of well-known ones - the characterisation ring oscillators. BCM283x has several free-running oscillators scattered around the die that are primarily used for CPU AVS - as each chip has a different speed, we need to adjust turbo-mode...
by jdb
Thu Feb 21, 2019 8:41 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 73
Views: 20077

Re: Analogue audio redux

The driver is specific to the onboard 3.5mm jack audio.
by jdb
Thu Feb 21, 2019 8:31 pm
Forum: Advanced users
Topic: Raspberry Pi SRAM
Replies: 21
Views: 1251

Re: Raspberry Pi SRAM

Yes, but is it direct mapped cache or fully associative or some level set associativity in between? What is the cache replacement policy? Depends on which RPi and which cache. For the RPi3's A53s the L1 I-caches are 2-way, the L1 D-caches are 4-way and the L2 cache is 16-way set associative. Replac...
by jdb
Tue Feb 19, 2019 2:28 pm
Forum: Off topic discussion
Topic: Is ARM doomed?
Replies: 298
Views: 11912

Re: Is ARM doomed?

Interestingly, for megacorps such as Apple and Qualcomm they have outgrown the ARM per-processor licensing model and gone straight for "architectural" licences where they get to design their own AARCH compatible cores. I would wager that economies of scale come into play here - if you're shipping 5 ...
by jdb
Mon Feb 18, 2019 4:24 pm
Forum: HATs and other add-ons
Topic: Does TV HAT support BBC Red Button using MHEG-5?
Replies: 5
Views: 965

Re: Does TV HAT support BBC Red Button using MHEG-5?

The TV hat works one layer down from MHEG-5. It's up to the video decode and presentation to parse overlays/subtitles/network information. There's no reason why it shouldn't work - it's all the same datastream.
by jdb
Mon Feb 18, 2019 4:22 pm
Forum: Off topic discussion
Topic: Is ARM doomed?
Replies: 298
Views: 11912

Re: Is ARM doomed?

fruitoftheloom wrote:
Mon Feb 18, 2019 1:51 pm

Poppycock and balderdash :roll:
If you don't have anything to say other than this inane comment, don't post.
by jdb
Sun Feb 17, 2019 6:48 pm
Forum: Off topic discussion
Topic: Finally found out why SD cards were so unreliable on early Pi
Replies: 6
Views: 837

Re: Finally found out why SD cards were so unreliable on early Pi

I wonder if he had a slip of the tongue and meant SDIO (not SPI) MMC controller. That would match. Interesting if so. Then again his notes say quite clearly SPI. SD cards can be accessed over SPI. It part of specification compliance - cards must implement this mode. Microcontrollers frequently use ...
by jdb
Fri Feb 15, 2019 2:56 pm
Forum: Off topic discussion
Topic: Order a special request Raspberry Pi :?:
Replies: 68
Views: 3123

Re: Order a special request Raspberry Pi :?:

To the OP: If the Raspberry Pi doesn't meet your requirements (32G RAM? Really?), I suggest buying something that does.
by jdb
Fri Feb 15, 2019 12:51 pm
Forum: Off topic discussion
Topic: Is ARM doomed?
Replies: 298
Views: 11912

Re: Is ARM doomed?

RISC-V displacing microcontroller-type cores (in-order, 1-wide issue, modest clockspeed) is very much happening - Western Digital are now using RISC-V cores in their storage controllers. ARM doesn't really have any feature differentiation in this segment, except for being widely supported in gcc/llv...
by jdb
Fri Feb 08, 2019 4:07 pm
Forum: General discussion
Topic: [RPI-3B+ USB interrupt issue] why there are so many interrupts from USB controller
Replies: 4
Views: 228

Re: [RPI-3B+ USB interrupt issue] why there are so many interrupts from USB controller

You are correct in stating that the frequency of interrupts does not decrease - the FIQ is used for two reasons 1) so that the general hard IRQ latency of Linux is avoided, as the USB hardware is very timing-sensitive and 2) so that the handler can be made as lightweight as possible. With Linux hand...
by jdb
Fri Feb 08, 2019 4:01 pm
Forum: General discussion
Topic: Pi 3A+ Schematic question
Replies: 6
Views: 300

Re: Pi 3A+ Schematic question

Missing from the 3B+ sheet but present on the 3A+ sheet is the arcane invocation "Make ADC traces accessible before shorting to GND" Also, I don't quite understand what AGND is for, since it doesn't appear anywhere other than round the PMIC, and not where I would have expected, at the audio subsyst...
by jdb
Fri Feb 08, 2019 3:13 pm
Forum: General discussion
Topic: [RPI-3B+ USB interrupt issue] why there are so many interrupts from USB controller
Replies: 4
Views: 228

Re: [RPI-3B+ USB interrupt issue] why there are so many interrupts from USB controller

From the boot log: [ 4.358325] dwc2 3f980000.usb: dwc2_check_params: Invalid parameter lpm=1 [ 4.365270] dwc2 3f980000.usb: dwc2_check_params: Invalid parameter lpm_clock_gating=1 [ 4.373351] dwc2 3f980000.usb: dwc2_check_params: Invalid parameter besl=1 [ 4.380368] dwc2 3f980000.usb: dwc2_check_par...

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