mfm/custom regs/track loader

snyp · 04 June 2006, 09:25

quick question.. if any of you guys could help..

what's the very least amount of mfm data i need to read to seek to any sector on a track?.. (we're talking cutting down to the absolute bare minimum.. saving even $10 bytes would help)..

Galahad/FLT · 05 June 2006, 11:02

You can't just read a sector, you have to load a track and then decode the relevant sector from there. Well technically, you could read and decode just the first sector, but if you wanted to read the 5th sector in a track, you must load and decode all the previous sectors.

Toni Wilen · 05 June 2006, 11:23

You could use DSKBYTR-custom register.. Even unexpanded A500 has enough CPU power to read and decode the data on the fly without need for temporary MFM buffer. (of course you can't have background effects, music etc..)

If I remember correctly, cracked "The Deep"'s loader uses this (really stupid) method.

snyp · 05 June 2006, 20:37

thanks guys..

from this advice i guess i'll try reading one byte at a time and then dumping it in fastmem out of my way.

ridiculous as it sounds, i can't spare 3-4k in chipmem with the situation i have.

musashi5150 · 06 June 2006, 16:27

Could I ask what you are doing? It sounds like something pretty interesting if you are using trackloaders and large amounts of chipram

snyp · 06 June 2006, 19:17

Quote:

Originally Posted by musashi5150

Could I ask what you are doing? It sounds like something pretty interesting if you are using trackloaders and large amounts of chipram

it's a graphics project.. um.. it kind of works with my own type of 'fractals' and random number generation. eventually i want the code to let the computer draw whatever it wants (within certain rules).

without adjusting the size of the display (which i really can't do) i need a multiple of $2800 chipram for each bitplane.. i decided to do away with any kind of access to the amiga's o/s libraries and use my own stuff after turning off all the interrupts. so a trackloader makes sense.

it's about 80% complete with my w32 version but i want to port it to 680x0..
here's a screenshot if you'd like to see.. point of interest is that the colours cycle, creating the illusion of 'movement' =)

musashi5150 · 06 June 2006, 19:34

Ahhh

I've seen this sort of fractal-cycle in some old demos (I'm sure yours is quite a bit more advanced though). Looks nice - I always love something pretty to look at

snyp · 06 June 2006, 19:37

Quote:

Originally Posted by musashi5150

Ahhh

I've seen this sort of fractal-cycle in some old demos (I'm sure yours is quite a bit more advanced though). Looks nice - I always love something pretty to look at

yep.. is oldskool with some (hopefuly) fresh ideas =)

musashi5150 · 06 June 2006, 19:39

BTW - is that tampon for your avatar?

snyp · 06 June 2006, 19:42

Quote:

Originally Posted by musashi5150

BTW - is that tampon for your avatar?

04 June 2006, 09:25	#1
snyp 'Difficult'. Join Date: May 2006 Location: No fixed abode Age: 46 Posts: 105	mfm/custom regs/track loader quick question.. if any of you guys could help.. what's the very least amount of mfm data i need to read to seek to any sector on a track?.. (we're talking cutting down to the absolute bare minimum.. saving even $10 bytes would help)..

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05 June 2006, 11:02	#2
Galahad/FLT Going nowhere Join Date: Oct 2001 Location: United Kingdom Age: 50 Posts: 9,016	You can't just read a sector, you have to load a track and then decode the relevant sector from there. Well technically, you could read and decode just the first sector, but if you wanted to read the 5th sector in a track, you must load and decode all the previous sectors.

05 June 2006, 11:23	#3
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,554	You could use DSKBYTR-custom register.. Even unexpanded A500 has enough CPU power to read and decode the data on the fly without need for temporary MFM buffer. (of course you can't have background effects, music etc..) If I remember correctly, cracked "The Deep"'s loader uses this (really stupid) method.

05 June 2006, 20:37	#4
snyp 'Difficult'. Join Date: May 2006 Location: No fixed abode Age: 46 Posts: 105	thanks guys.. from this advice i guess i'll try reading one byte at a time and then dumping it in fastmem out of my way. ridiculous as it sounds, i can't spare 3-4k in chipmem with the situation i have.

06 June 2006, 16:27	#5
musashi5150 move.w #$4489,$dff07e Join Date: Sep 2005 Location: Norfolk, UK Age: 42 Posts: 2,351	Could I ask what you are doing? It sounds like something pretty interesting if you are using trackloaders and large amounts of chipram

06 June 2006, 19:34	#7
musashi5150 move.w #$4489,$dff07e Join Date: Sep 2005 Location: Norfolk, UK Age: 42 Posts: 2,351	Ahhh I've seen this sort of fractal-cycle in some old demos (I'm sure yours is quite a bit more advanced though). Looks nice - I always love something pretty to look at

06 June 2006, 19:39	#9
musashi5150 move.w #$4489,$dff07e Join Date: Sep 2005 Location: Norfolk, UK Age: 42 Posts: 2,351	BTW - is that tampon for your avatar?

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