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stiggity
Account closed
Registered: Jul 2013
Posts: 5 |
c64 garbage collection, NEED HELP!!!
I came across a real nice "aftermarket" c64 garbage collection routine. I spent 2 hours on the source, and got it able to
compile in my assembler (64tass). but, all comments are in
German. Im writing a BBS program for the 64, and it runs and
works, but it will pause for 10/12/15 seconds here and there. And anyone not knowing its collecting garbage, may
drop carrier. I would like to intermingle this code, into my own project, but believe its a little above my skills level. If anyone is into c64 telecom, and thinks they could help me out, be my guest. I can describe, and explain how my memory is laid-out, with the BBS. So if you think your good, and believe this code _can_ be intermingled, I can fully credit you in docs, manual, website, and email support. Thanks. Id rather go back and forth via E-mail, rather than posting the source here. I'm safe! :)
-Thanks,
--Steve
stiggity99(@)Comcast.net |
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Oswald
Registered: Apr 2002
Posts: 5094 |
AgentFriday, first two, mostly the stock tho. but knowing what it does in general would also help understand why it is so slow. I was never really aware of this "string problem" in c64 basic so far. |
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TheRyk
Registered: Mar 2009
Posts: 2246 |
In a German forum we did a fun coding contest recently, hosted by S.E.S/crest. winner was who manages to let the GC be occupied as long as possible.
Maybe you like to have a look at the results, maybe for fun, but maybe it even helps to understand. Though it's all in German, the first posting contains the .D64 Image with all the entries.
http://www.forum64.de/wbb3/board25-coder-unter-sich/board308-pr.. |
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AgentFriday
Account closed
Registered: May 2012
Posts: 4 |
I think there are probably a couple books that document how garbage collection works on the C64 at a somewhat high level, but I couldn't name any right now.
I'm having some fun with this one, so I'm thinking of doing a blog post on the subject, as well as updating my ROM annotations to cover the GC routine. If/when I do, I'll post a notification to this thread.
I'm looking into turning the Image BBS GC routine into a seamless fix that anybody could use (i.e., wedge it in, forget about it). It kinda sucks to have to build in periodic checks to see if the heap is getting nearly full. |
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Rough
Account closed
Registered: Feb 2002
Posts: 1829 |
Quoting TheRyk
http://www.forum64.de/wbb3/board25-coder-unter-sich/board308-pr..
I'm not sure if this is really cool or complete dorky, but I'd rather pick the first option. |
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TheRyk
Registered: Mar 2009
Posts: 2246 |
not at all kewl, was some kind of nonsense compo, MEANT to be dorky to "honor" some guy who back then terrorized that forum with REALLY dorky and mostly useless GC "solutions" in BASIC and ASM :) |
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Rough
Account closed
Registered: Feb 2002
Posts: 1829 |
Talking about dorky:
The program which made me know the garbage collection is
Quote: Stamping Collection Kit: Erfassen und Katalogisieren von Briefmarkensammlungen. Druckausgabe von Bestands- und Fehllisten. Steuerung per Puli-down-Menus (64'er-Sonderheft 15).
It was pretty well done for its time and being Basic. |
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Tao
Registered: Aug 2002
Posts: 115 |
Quote: And I thought Tao modded C*Base is the best there is anyhow nowadays? :)
It is :P But I don't use a custom GC routine. I expect most BBS programs do the same thing as C*Base -- call the standard garbage collector from the wait screen. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
i actually remember driving to moses for hacking a fast garbage collection into c*base so it wouldnt be vulnerable to the good old wait-at-prompt-for-minutes problem :) |
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JackAsser
Registered: Jun 2002
Posts: 2014 |
Found this floating around: http://www.atarimagazines.com/compute/issue49/422_1_Garbage_Col.. |
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soci
Registered: Sep 2003
Posts: 480 |
As the article says this is a solved problem in later basic versions.
The solution was to put a "back" pointer right after the allocated string which points to the string length and pointer of the original variable/array element.
Deleted strings reuse this pointer for noting down the size of the deleted string by using a special pointer of $ffxx.
With this it's trivial to garbage collect in O(n) time.
Just start from the end of string area. Either there's a normal back pointer, this can be used to find out how big the string is and where to adjust it's pointer after the move.
Or it could be a special pointer ($ffxx) then it's a hole, skip it over, the length is the xx part.
Then continue compaction until the beginning of string area is reached.
This costs 2 extra bytes per string of course. And the amount of extra code which fixes/replaces the original string handling... |
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