Log inRegister an accountBrowse CSDbHelp & documentationFacts & StatisticsThe forumsAvailable RSS-feeds on CSDbSupport CSDb Commodore 64 Scene Database
You are not logged in 
CSDb User Forums


Forums > CSDb Discussions > IEEE article on the c64 from 1985
2017-10-10 15:49
Kruthers

Registered: Jul 2016
Posts: 8
IEEE article on the c64 from 1985

Came across this and thought other people might find it interesting. There are a few things in there that I never heard before, like why the NTSC model changed from 64 to 65 cycles per line, why the drive was so slow, and a video "sparkle" bug on the original machines that actually triggered sprite collisions...

Anyway, enjoy:

https://spectrum.ieee.org/ns/pdfs/commodore64_mar1985.pdf
 
... 1 post hidden. Click here to view all posts....
 
2017-10-10 20:55
Cruzer

Registered: Dec 2001
Posts: 893
Interesting and well-written.
2017-10-10 22:36
Oswald

Registered: Apr 2002
Posts: 4092
I've seen bits and pieces of this, what caught my eye is the diagram showing where sprite and gfx fetches happen. Looks like this info was out there since ages :) I was only aware of these fetch places since VIC article came out.
2017-10-11 20:46
ThunderBlade

Registered: Jan 2002
Posts: 49
Nice, thanks!
2017-10-12 07:03
ChristopherJam

Registered: Aug 2004
Posts: 656
Thanks, that was a really interesting read.

Scary to read that we very nearly only had 57 cycles per line to work with, with no CPU cycles whatsoever on bad lines with all sprites enabled.

There were at least three times as many ex Commodore personnel working at Ensonique than I'd realised, too - the ESQ1 beside my desk is an even closer relative to the C64 than I thought!
2017-10-12 09:01
Krill

Registered: Apr 2002
Posts: 843
Quoting ChristopherJam
Scary to read that we very nearly only had 57 cycles per line to work with, with no CPU cycles whatsoever on bad lines with all sprites enabled.
I've missed that bit when first reading the article, then spent a while to find it. The only reference i found is in the "Sprites: making animation easy" box: "Moving across the video line, you've got 63 microseconds to play with. I was going to use memory running at just under 2 MHz, meaning only 114 memory fetches per line — period."

Is this where you gleamed this information from? Very attentive reading! :)

In this context, it's quite lucky (for us) that they later changed the timing to have 126 memory fetches per line AND lacked the time to change the sprite circuitry. What good are 4 chars wide sprites if you have no CPU cycles left with all 8 of them enabled on a badline? :D

That said, i don't remember having consciously done any VIC tricks on a badline with all 8 sprites enabled, and the maximum number of sprites over FLI so far is 6, if i haven't missed or forgotten an update on that. Hmm...
2017-10-12 09:07
Krill

Registered: Apr 2002
Posts: 843
Addendum: 6 sprites over "full-width" (37 chars) FLI. I've just remembered Soul — which features 8 sprites over FLI, but the bitmap is narrowed down due to way too late DMA. :)
2017-10-12 09:13
Oswald

Registered: Apr 2002
Posts: 4092
Quote: Addendum: 6 sprites over "full-width" (37 chars) FLI. I've just remembered Soul — which features 8 sprites over FLI, but the bitmap is narrowed down due to way too late DMA. :)

or shifli from krestology which was first :P
2017-10-12 09:22
ChristopherJam

Registered: Aug 2004
Posts: 656
Quoting Krill
The only reference i found is in the "Sprites: making animation easy" box: "Moving across the video line, you've got 63 microseconds to play with. I was going to use memory running at just under 2 MHz, meaning only 114 memory fetches per line — period."

Yes, that and the following paragraph about dividing 8 sprites into the remaining 34 fetches, to get the 24 pixel wide sprite resolution.

Quote:
Very attentive reading! :)

Thanks! I spread it over a few days..

Quote:
In this context, it's quite lucky (for us) that they later changed the timing to have 126 memory fetches per line AND lacked the time to change the sprite circuitry. What good are 4 chars wide sprites if you have no CPU cycles left with all 8 of them enabled on a badline? :D

Exactly! But it's also nice having more than 14 cycles available on no-sprites badlines; there wouldn't have been enough time for full width FLI, or various bitmap stretchers.

Quote:
That said, i don't remember having consciously done any VIC tricks on a badline with all 8 sprites enabled, and the maximum number of sprites over FLI so far is 6, if i haven't missed or forgotten an update on that. Hmm...


I can't remember if anyone's opened borders on a badline with all sprites present?

But yeah, the only time I've so much as seven sprites plus FLI was for the unrestricted 16 colour mode in Reutastic, and that's only 36 MCM pixels wide even with an REU…
2017-10-12 09:25
Krill

Registered: Apr 2002
Posts: 843
Quoting Oswald
or shifli from krestology which was first :P
Firstie schmirstie… Didn't say Soul was first. :) And Krestology, oh my… if there ever was a demo benefitting from warp mode, this is it. :D
2017-10-12 10:12
Oswald

Registered: Apr 2002
Posts: 4092
yeah, kresto was slow, but those 320x modes started the revolution that ended with nufli :) I couldnt believe my eye back than, 320x without flicker and many colors was huge.
Previous - 1 | 2 - Next
RefreshSubscribe to this thread:

You need to be logged in to post in the forum.

Search the forum:
Search   for   in  
All times are CET.
Search CSDb
Advanced
Users Online
TomoAlien
ZeSmasher/F4CG
Karmic/HVSC/ONS
Twoflower/ΤRIΛD
Guests online: 54
Top Demos
1 Uncensored  (9.7)
2 Edge of Disgrace  (9.7)
3 Coma Light 13  (9.6)
4 The Shores of Reflec..  (9.6)
5 Lunatico  (9.6)
6 Quad Core 100%  (9.5)
7 Comaland 100%  (9.5)
8 Incoherent Nightmare  (9.5)
9 Wonderland XII  (9.5)
10 Comaland  (9.5)
Top onefile Demos
1 Pandemoniac Part 2 o..  (9.6)
2 Synthesis  (9.6)
3 Dawnfall V1.1  (9.5)
4 Daah, Those Acid Pil..  (9.5)
5 Field Sort  (9.4)
6 Treu Love [reu]  (9.4)
7 Dawnfall  (9.3)
8 Globe 2016 [reu]  (9.3)
9 KAOS 64  (9.3)
10 Hardware Accelerated..  (9.2)
Top Groups
1 Booze Design  (9.4)
2 Censor Design  (9.4)
3 Oxyron  (9.4)
4 Crest  (9.3)
5 Finnish Gold  (9.3)
Top Diskmag Editors
1 Jazzcat  (9.5)
2 Peter  (9.4)
3 Newscopy  (9.4)
4 Remix  (9.3)
5 Vengeance  (9.3)

Home - Disclaimer
Copyright © No Name 2001-2017
Page generated in: 0.266 sec.