Forum comments in chronological order

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Jul 2018

GCR decoding on the fly

Wed 4-Jul-2018 16:22
Thanks for putting this together. Great article.

Spindle v2

Fri 6-Jul-2018 03:53
Amazing loader LFT, blazingly fast! We used it in Delirious 11 (Genesis Project).

The TTY demystified

Wed 18-Jul-2018 22:44
Thanks for the introduction of TTY!

Massively Interleaved Sprite Crunch

Tue 24-Jul-2018 05:55
If your crunched sprite starts at offset 0x35 what do you do to get there to begin with? Do you start at 0 with the FG color set to black or in the top border and do some dummy crunch to traverse the graph to the right starting point?

Was wondering that myself. I guess that's what he means. Im unsure of the benefit of this though, as opposed to simply changing the sprite definition pointer. The sprite hasnt ended, and loops back... so I guess you can change the def and effectively have the sprite "start again". It's still the same sprite though, as opposed to the 17 pixel sprites that are the minimum.

The sprite definition pointer is stored as an 8 bit value that is multiplied by 64 to produce an offset into the selected VIC bank. You don't get per-byte granularity.

So to me this is still a mystery.

Pushing Onwards: Return of the Chipophone

Fri 27-Jul-2018 10:40
I'd love to hear you take on "World Theme 1" from the NES game "Silver Surfer". Composed by Tim and Geoff Follin.

I think it would be a challenge :)



Fri 27-Jul-2018 10:43
Great version of a Hubbard favourite :)

How much time do spend preparing/practising before recording a song?


The TTY demystified

Sat 28-Jul-2018 02:46
I thought that it would be helpful to leave a comment about something that confused me.

Why, when -tostop was set on the terminal, did the editor get sent a SIGTTOU but the backgrounded (sleep 5; echo ...) did not?

I used strace on the editor process and found that it was calling ioctl() right before receiving a SIGTTOU:

--- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, ...} ---
ioctl(5, SNDCTL_TMR_STOP or TCSETSW, {...}) = ...
--- SIGTTOU {si_signo=SIGTTOU, si_code=SI_KERNEL} ---
--- stopped by SIGTTOU ---

In the Linux kernel source, I found that the code that handles an ioctl request for TCSETSW will unconditionally check if the process is in the foreground process group of the tty, and send SIGTTOU if it isn't.

But, at least in the write handler for N_TTY, the same check is *only made if the TOSTOP bit is set*.

So, -tostop will allow a backgrounded process to write to the terminal but it will not allow a backgrounded process to call ioctl(..., TCSETSW, ...) on it.


Tue 31-Jul-2018 10:10
I know the answer is "she".