Prop Pox

A city affected by prop pox; note the similiarity to the city on low graphics settings.

Prop pox is a term for popular problem affecting SimCity 4's Save Games which causes props to gradually disappear from the tile. The first submittions of the case where posted in late April/early May by BruceAtkinson, Snorrelli and Fledder200. After the series of tests, community's member bap, posted the explanation of the problem on SC4D's forums.

An Explanation

Early tests (2007-early 2009)

After the first alarming comments about the problem were posted, immediately the tests on the causes of the prop pox have been started by different members of the community. What was learned in that period of time can be summarised into the following seven points:

1. The prop pox is most definitely not a graphical bug, thus it can't be resolved by just tweaking the graphical settings of the game nor the graphic card.

2. It isn't a kind of some computer issue or software conflict. Defragmenting the disc and increasing the virtual memory don't have any effects on the problem.

3. The problem isn't exclusive to one computer system. It can affect game running on the machine with Windows 2000, XP, Vista or even Macintosh.

4. Hardware settings are not responsible for the prop pox, as it can affect games running on all kinds of processors, sound & graphic cards, etc.

5. Occurances of the problem are most of the time noticed on the big (4km x 4km) tiles. It's not a matter of population, traffic nor density, however.

6. The problem lies in the city save file. It has been noted that the city files affected by the prop pox shrink by 200 to 400kb, and then gradually continues to shrink each time the game is saved. As it was discovered that props are stored in the subfile of type 2977aa47 (also known as the network subfile) which grows every time the city is saved, it would be logical if that subfile shrank with the rest of the city file. Thus, these 200 to 400kb are props lost in the process of saving the tile.

7. It was speculated that it was a memory overflow somewhere which is corrupting the city save file. Two possible explanations where publicated, one saying that it was an EP1 update program, and another that it was the plugins folder infected by the multiple definitions of the same prop.

New Revelations (2009)

On the 24th of February, bap posted a very accurate and easy to understand analysis of the problem. Basing on the already known information, and his own observations, he came to the conclusion that it were the modified versions of original, in-game Maxis' props. This theory has been called 'prop theory', and is known largely known as the most probable one. It was also concluded that the main, most popular file causing this problem are the Pegasus' CDK3-OWW2 lots, or rather props included in them, since some are the modified (time-depending) versions of the Maxis' props, which add to the city save file extra 78kb everytime the city is saved. It was also found out that the once affected tile can't be recovered, though it can be avoided by editing peg's CDK3-OWW2 files in iLive's Reader, or by downloading fixed versions of the previously downloaded files.

Despite those findings, however, the discussion is still on, as the 'prop theory' isn't proclaimed as the definitive one, yet it is most probable.

Controversies

Following the publication of bap's explanation of the prop pox it has arousen numerous controversies among several community members, including Pegasus himself. On SimPeg he had written a post regarding the bap's results and generally prop pox in general. He has expressed a very skeptical point of view towards both, by saying that the 'prop theory' is false, and that it's also NAM which adds to the network subfile size.

What causes prop pox, and how to prevent it