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taper
Registered: Dec 2001
Posts: 119 |
Event id #2391 : The 2015 REU Compo
Welcome to the 2015 REU Compo --- Hosted by LFT, Ruk and Taper!
See the event-page on: The 2015 REU Compo
Your mission is to create the most awesome one-file demo that runs on a standard C64 with a 512 kB REU and no disk drive.
Background
==========
The Commodore RAM Expansion Unit (REU) is a cartridge that provides secondary storage to the C64. It was introduced at CES in 1985. The memory in the REU cannot be accessed directly from the CPU (hence
"secondary"). Instead, the CPU must instruct the REU to transfer a given amount of data to or from the cartridge. The REU then takes over the bus, stalling the CPU, and transfers one byte per cycle.
This is basically all there is to it. Apart from the extra storage, the REU does not make the C64 faster or more powerful---although see below for some intriguing possibilities.
The largest REU available from Commodore (the 1750) was equipped with 512 kB of RAM. Nowadays, it is possible to emulate REUs with as much as 16 MB, e.g. using VICE or the 1541 Ultimate. Even though you can only use 512 kB in this competition, there should be no problems using
the RAM expansion features in the 1541U/1541U-II, Chameleon64 or any other device fully compatible with the Commodore 1750 REU.
Rules
=====
1. Your entry must be in .PRG format with a BASIC header. The file must load to address $801, and end before it reaches the I/O area at $d000. The gives a maximum file size of 51201 bytes.
2. You may assume that a REU of at least 512 kB is available.
3. Your entry must work with a larger REU (i.e. you cannot assume that the upper address bits are ignored). You may not use the extra RAM available in such configurations.
4. You cannot make any assumptions about the initial contents of REU memory.
5. Your entry must work on a real C64 with a real 512 kB REU from Commodore. Please keep in mind that there could still be bugs in the emulators.
6. Deadline is set to 2015-12-31 at 23:59 in a time zone of your choice. Your contribution needs to be mailed to reu@wuff.se to be accepted. You are free to create a CSDb entry for your contribution, else we will do it for you.
7. Immediately following the deadline, voting will take place on CSDb during a period of two weeks. Anonymous votes will be counted. We allow self-voting unless you have multiple personalities.
Suggestions
===========
For your inspiration, here are some ways in which a C64 demo might benefit from an REU:
Obviously, the extra RAM is useful. For instance, the demo might pre-compute large amounts of sprite graphics, and then quickly retrieve a subset of the data just before it's needed.
The fast transfer rate could be used to speed up scrolling operations: You can copy a large bitmap from the C64 to the REU, and then back again at a slightly different address.
Last but not least, the REU has a mode where every byte in a transfer gets written to the same destination address. This can be used to display graphics using the idle byte, for instance. The target address
could also be an I/O register, and this might enable some new VIC tricks.
Technical information
=====================
Please refer to the following documents for details about the REU programming interface:
http://www.zimmers.net/anonftp/pub/cbm/documents/chipdata/progr..
http://codebase64.org/doku.php?id=base:reu_registers
Happy hacking!
/LFT, Ruk & Taper |
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Dane
Account closed
Registered: May 2002
Posts: 421 |
Current state: a few preview parts, no gfx or art direction, no soundtrack. Some motivation would be nice. :) |
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Stinsen
Registered: Feb 2012
Posts: 73 |
Quote: Current state: a few preview parts, no gfx or art direction, no soundtrack. Some motivation would be nice. :)
Dane? No soundtrack? My eyes must be playing me a joke. :D |
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Dane
Account closed
Registered: May 2002
Posts: 421 |
It's only October! |
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lft
Registered: Jul 2007
Posts: 369 |
Quoting ShadowI did not quite get from the rules if entries were to be mailed and then released by the organizer after dec 31, or if we can mail them but also add them to CSDb right away?
Official statement from the organisers: Yes, it is OK to publish and add a release to CSDb before the deadline.
If you publish now, but wish to compete with a different version that you mail to us later, it might be a good idea to clarify this in your mail. Just so we don't mix up the versions.
Thanks for participating! |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Did someone have a chance to test run my entry (Reutozoom)on a real REU?
I developed it using WinVICE and testing on my C64 with 1541U2, and never had any problems.
Then when showing it on the Mysdata gathering, Hedning had managed to find a 512kb REU, so we could run it on real vintage hardware, and it worked fine.
However, later that night after some more people had arrived, we tried it again, and then there were strange bugs, to me it looked like one bit per byte had garbage data, but only for the top half of the memory!
Resetting and reloading didn't help. We unplugged the REU and tested with a 1541U2, and it worked fine again.
Later we plugged in the REU again, and then it worked.
We chalked it up to faulty hardware, since it seemed to run fine when the REU had some "rest" to cool down.
Anyway, it still would be good to know that this is the case and it's not me having done something stupid in the code. |
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Grue
Registered: Dec 2001
Posts: 154 |
Commodore sold REU's with beefier psu, I think for a reason. Did you have better psu when you tried running with real REU? |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
You might be on to something there! I don't know if that C64 was running with just a standard power supply, but I think there's a big chance that it did. |
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hedning
Registered: Mar 2009
Posts: 4618 |
What?! You know me better than that, Shadow. ;) No way I ran it on a standard PSU - haven't done that for 1 year now. It ran on a Ray Carlsen PSU, which should have enough cream to run a SuperCPU at least (according to the specs). It is well known for being the best PSU around. What could be the issue is that the REU is indeed old and could be flakey - it is Walker's old modified (expanded) REU, upgraded to 1MB (I think). I haven't really used it for anything else. I will try the demo again a couple of times today (I'm home from work anyway). |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
My deepest apologies - I should not doubt your excellent hardware collection! :) |
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hedning
Registered: Mar 2009
Posts: 4618 |
Quote: My deepest apologies - I should not doubt your excellent hardware collection! :)
Haha. No prob... But anyway. Will give you some more feedback after some rounds here at home. |
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