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by jahboater
Tue Feb 11, 2020 10:43 am
Forum: Beginners
Topic: Creating an Operating System on the Raspberry Pi
Replies: 36
Views: 1575

Re: Creating an Operating System on the Raspberry Pi

The word "shall" above is interesting: since "long long" is guaranteed to exist, it implies that int64_t must also exist. "long long" could be 72 bits, include padding, or be stored sign-magnitude. In these cases, int64_t will either not exist, or it will be slower than the native types. For 72-bit...
by jahboater
Mon Feb 10, 2020 8:45 pm
Forum: General discussion
Topic: Reasoning behind dual Micro HDMI, and potential future alternatives?
Replies: 125
Views: 10824

Re: Reasoning behind dual Micro HDMI, and potential future alternatives?

The "official" micro HDMI able is only £5 and works fine.
by jahboater
Mon Feb 10, 2020 7:48 pm
Forum: Beginners
Topic: Creating an Operating System on the Raspberry Pi
Replies: 36
Views: 1575

Re: Creating an Operating System on the Raspberry Pi

Here's one from C99: "int64_t" works identically on all platforms regardless of hardware support. ISO/IEC 9899:* §7.[18|19|20].1.1.3 These types are optional. However, if an implementation provides integer types with widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that ...
by jahboater
Mon Feb 10, 2020 7:00 pm
Forum: Raspbian
Topic: how to put together an os?
Replies: 8
Views: 232

Re: how to put together an os?

Hi All My understanding is the OS is an assemble of different tools like kernel to manager resource, gcc for tool development and different application software such as chrome, emacs? I am wondering if there is a tutorial which show how to assemble an os by yourself? Thank you for your inputs. Best...
by jahboater
Mon Feb 10, 2020 6:22 pm
Forum: Beginners
Topic: Creating an Operating System on the Raspberry Pi
Replies: 36
Views: 1575

Re: Creating an Operating System on the Raspberry Pi

In what way is C today any "safer" than it was back in K&R days? Trivial example: in the bad old days people used to do all kinds of questionable things like storing pointers in integers (probably because that was what you did in B and BCPL). That sort of thing is now unthinkable. The "const" keywo...
by jahboater
Mon Feb 10, 2020 5:24 pm
Forum: Troubleshooting
Topic: Frustrated noob! Raspbery Pi 4 b not booting
Replies: 18
Views: 734

Re: Frustrated noob! Raspbery Pi 4 b not booting

I have gone to the Raspian page, re-imaged the SD card with NOOBS and re-tried, same result. That doesn't sound like what @pcmanbob suggested. 1) you don't image NOOBs with etcher 2) he suggested downloading Raspbian itself and using etcher to image that Forget about NOOBs and install Raspbian dire...
by jahboater
Sun Feb 09, 2020 9:29 pm
Forum: Beginners
Topic: case - fan compatibility
Replies: 14
Views: 897

Re: case - fan compatibility

maintaining the RPi SoC's running temp below 40C (even at stressed condition) does not violate any known norms... does it? others prefer theirs to run at 60C, others at 50C..... others don't mind any temp at all. I prefer below 35C at 27C ambient.... so its down to each user's preference..... Yes I...
by jahboater
Sun Feb 09, 2020 7:27 pm
Forum: Beginners
Topic: Fastest boot version of Raspbian ...... ?
Replies: 14
Views: 513

Re: Fastest boot version of Raspbian ...... ?

1) Pi 3B+ never ( for me ) has temperature issues . Yes, the 3B+ was much better thermally speaking than the 3B. But it still used the old 40nm node size. The Pi4 had a die shrink to 28nm and now we have the fancy new DVFS firmware, it runs much cooler than the 3's did. At least mine does. There is...
by jahboater
Sun Feb 09, 2020 5:34 pm
Forum: General discussion
Topic: My Pi4B has a BCM2835?
Replies: 5
Views: 426

Re: My Pi4B has a BCM2835?

That's just the way Linux reports it. If I'm remembering correctly, the problem may be upstream with Debian. All models report the same thing, but for all the quad-core models it's wrong. You have what you're supposed to have in a Pi4 (Broadcom BCM2711, Quad core Cortex-A72 (ARM v8) 64-bit SoC @ 1....
by jahboater
Sun Feb 09, 2020 5:28 pm
Forum: Beginners
Topic: Fastest boot version of Raspbian ...... ?
Replies: 14
Views: 513

Re: Fastest boot version of Raspbian ...... ?

You’ll always want to run the latest versions of the OS. and seem to offer no advantage ? Seriously ? Buster is required to even run on the Pi4 Apart from the support and security mentioned above, there are much later versions of important software. For me, as a programmer, buster comes with Python...
by jahboater
Sun Feb 09, 2020 2:12 pm
Forum: General discussion
Topic: No /tmp filesystem
Replies: 7
Views: 290

Re: No /tmp filesystem

If you limit the maximum size of /tmp or /var/log with the "size=" option, you can ensure the system will still run (reasonably) happily even when they are full.

Sounds like you need a 4GB Pi4!
by jahboater
Sun Feb 09, 2020 2:03 pm
Forum: Beginners
Topic: Fastest boot version of Raspbian ...... ?
Replies: 14
Views: 513

Re: Fastest boot version of Raspbian ...... ?

You may add

initial_turbo=30

to config.txt which will run the CPU's at maximum speed for the first 30 seconds.
It helps boot times slightly.
by jahboater
Sun Feb 09, 2020 1:57 pm
Forum: General discussion
Topic: No /tmp filesystem
Replies: 7
Views: 290

Re: No /tmp filesystem

What happens if a /tmp filesystem uses up the allocated memory - the Pi grinds to a halt, or frantic swapping? tmpfs is different from ramfs in that it resides in "virtual" memory. And the virtual memory occupied is that used by the files only. There is a slight overhead for an empty tmpfs filesyst...
by jahboater
Sun Feb 09, 2020 1:23 pm
Forum: Troubleshooting
Topic: initramfs-tools problem on raspbian
Replies: 4
Views: 164

Re: initramfs-tools problem on raspbian

DougieLawson wrote:
Sun Feb 09, 2020 12:23 pm
Get a new SDCard and build Buster 2020-02-05 on that.
+1

You then have the old card as a backup of course.

You may place the old card in a USB card reader, plug it into the Pi, and copy over any files you want.
by jahboater
Sun Feb 09, 2020 1:13 pm
Forum: Beginners
Topic: Fastest boot version of Raspbian ...... ?
Replies: 14
Views: 513

Re: Fastest boot version of Raspbian ...... ?

To measure boot time use systemd For example: $ systemd-analyze Startup finished in 889ms (kernel) + 14.493s (userspace) = 15.383s graphical.target reached after 14.456s in userspace For more info about which services take the longest to start: systemd-analyze blame and systemd-analyze critical-chain
by jahboater
Sun Feb 09, 2020 1:03 pm
Forum: Beginners
Topic: case - fan compatibility
Replies: 14
Views: 897

Re: case - fan compatibility

I am not sure how they "see" this heat increase though. Do they physically sense it or see it through software, I have no idea. I will have to wait and see for myself. To see the temp you do this: vcgencmd measure_temp Before worrying about fans and cooling, get your Pi4 and use it! Install the lat...
by jahboater
Sun Feb 09, 2020 9:51 am
Forum: Troubleshooting
Topic: NO Overclock possible
Replies: 10
Views: 449

Re: NO Overclock possible

Have you applied any extra voltage? over_voltage=2 arm_freq=1600 You can go up to "over_voltage=6", but it really should not be needed for a small overclock. My Pi4 is unconditionally stable at 1600MHz with no over_voltage at all. You are using the "official" PSU which is great, consider also (1) co...
by jahboater
Sat Feb 08, 2020 5:16 pm
Forum: General discussion
Topic: need to upgrade python
Replies: 11
Views: 555

Re: need to upgrade python

Heater wrote:
Sat Feb 08, 2020 5:13 pm
If you really need to keep 2.7.x & 3.5.3 working as well you are in a big mess and likely to drive yourself crazy!
Perhaps investigate why your software is dependent on specific versions - its usually a bad thing.
And Python 2.x is officially end of life.
by jahboater
Sat Feb 08, 2020 5:09 pm
Forum: General discussion
Topic: No /tmp filesystem
Replies: 7
Views: 290

Re: No /tmp filesystem

You need to add it yourself for Raspbian.
I append this to /etc/fstab

Code: Select all

tmpfs /tmp tmpfs defaults,noatime 0 0
tmpfs /var/log tmpfs defaults,noatime,size=16m 0 0
by jahboater
Sat Feb 08, 2020 5:06 pm
Forum: Troubleshooting
Topic: NO Overclock possible
Replies: 10
Views: 449

Re: NO Overclock possible

You have not said what settings you tried. No over-clock is ever guaranteed. Its usually best to start with a tiny increase and raise it slowly, checking carefully for stability with each step. I think the latest firmware has fixed the GPU over-clock problem by the way. I don't know if you should ru...
by jahboater
Fri Feb 07, 2020 8:29 pm
Forum: Beginners
Topic: Creating an Operating System on the Raspberry Pi
Replies: 36
Views: 1575

Re: Creating an Operating System on the Raspberry Pi

W. H. Heydt wrote:
Fri Feb 07, 2020 7:54 pm
Student exercise... C is derived from B. B is derived from BCPL.
and BCPL was derived from CPL (Basic CPL).
W. H. Heydt wrote:
Fri Feb 07, 2020 7:54 pm
What is the next language called?
You mean the debate: should it be called D or P ?
by jahboater
Fri Feb 07, 2020 6:47 pm
Forum: Beginners
Topic: Creating an Operating System on the Raspberry Pi
Replies: 36
Views: 1575

Re: Creating an Operating System on the Raspberry Pi

Heater, Is it so this situation is not going to change, forever? I hope not. C definitely has evolved of course - but slowly and carefully. Its a far safer, more portable, and more usable language than K&R was - all done without invalidating all the billions of lines of existing code. (unlike Python...
by jahboater
Fri Feb 07, 2020 2:47 pm
Forum: General discussion
Topic: Removing LEDs for dark-use Pi
Replies: 17
Views: 946

Re: Removing LEDs for dark-use Pi

Seems a waste of power to paint over the LED's, I'd rather turn them off. I use this in config.txt for the Pi4 - it seems to work, but there is probably a better way. # Disable the PWR LED dtparam=pwr_led_trigger=none dtparam=pwr_led_activelow=off # Disable the Activity LED dtparam=act_led_trigger=n...
by jahboater
Fri Feb 07, 2020 9:19 am
Forum: Beginners
Topic: Creating an Operating System on the Raspberry Pi
Replies: 36
Views: 1575

Re: Creating an Operating System on the Raspberry Pi

Learn C All the successful, widely used, operating systems are written in C for good reason (e.g. Windows, Linux, MacOS, UNIX etc). The C language was created specifically for writing operating systems (and compilers, editors, and other system tools). Some knowledge of assembler may be useful too. S...
by jahboater
Wed Feb 05, 2020 11:50 pm
Forum: C/C++
Topic: what does this c code mean?
Replies: 10
Views: 1159

Re: what does this c code mean?

HermannSW wrote:
Wed Feb 05, 2020 11:23 pm
I got used to macros in C in the early 90s.
Ditto - but its all changed nowadays.

We use enum's instead of #define manifest constants.
We use (mostly) functions instead of macros - modern compilers inline them to just the same code, but with much better and safer semantics.

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