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The 2015 REU Compo

- Massive RAM overload!

Event Type :
Standalone Compo

Dates :
25 July - 31 December 2015

Organizers :
Lft, Ruk, Taper

Competition Results :

C64 Demo
PlaceReleaseDLCSDb ratingPub only
1Treu Love by Booze DesignDownload9.49.8
2Reutastic by ChristopherJamDownload7.6
3Reutozoom by Genesis ProjectDownload7.8
4Samareu by Samar ProductionsDownload7.3

Productions released outside compos :
Reutastic (REU Release)

User Comment
Submitted by ruk on 17 January 2016
The 2015 REU Compo - Official Results

We salute the four brave groups who decided to take on the
challenge and compete in the 2015 REU competition!

All four contributions worked on a real C64 equipped with a
Commodore REU, even though the Booze Design demo did suffer
from a few bugs since it was not tested on real hardware
during development. Thus, we can conclude that the REU
emulation in neither Vice nor the 1541 Ultimate II is to be fully trusted.
Hopefully these emulation issues can be resolved some day now that there is a test case!

Despite a few bugs on a real machine (which have since been
resolved), Booze decisively landed the gold medal with
Treu Love, which scored no less than 9.5 points on CSDb.

Second place and the silver medal went to Reutastic from
Christopher Jam, scoring 7.8 points and thus just surpassing our
bronze medal runners-up in Genesis Project who were awarded 7.7

On fourth place, but still scoring a respectable 7.2 points, we
find Samareu from Samar Productions.

The organisers wish to thank all the competing groups who made
an effort and graced us with the productions!

Taper, Lft & Ruk

User Comment
Submitted by 6R6 on 2 January 2016
Tested all demos on my C64C with Xpander 3 (cartridge port expander), using RetroReplay + Super 1750 Clone (512kb). PSU is the big heavy brick that comes with the 1764 reu.

These demos worked fine: Samareu, Reutastic and Reutozoom.

The Booze Design demo has two flawed parts:
1. The scroller part with 7 sprites in sideborders over a multicolor picture.
2. The same sprite scroller in sideborders over a fpp effect.
The problem is timing and black lines in the open borders.

User Comment
Submitted by lft on 13 October 2015
Addendum to the rules: It is OK to make a public release and add it to CSDb before the deadline. You still have to mail your entry to us.

User Comment
Submitted by Perplex on 25 July 2015
Great idea!

User Comment
Submitted by JackAsser on 25 July 2015

User Comment
Submitted by taper on 25 July 2015
Welcome to the 2015 REU Compo - Hosted by LFT, Ruk and Taper!

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.

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.

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

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.

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:



Happy hacking!

/LFT, Ruk & Taper
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