KRZ  I noticed that my hard drive space was rapidly vanishing today. Upon investigation I discovered that the HiARCS database file in the HiARCS folder had swelled to over 100GB, leaving me with 0kb of free space. There don't appear to be any setting changes which can prevent this either.  
(Version 6.1.6)

IGAUCHO  One of the absolute best chess programs.

I'd just like to point out that only the HIARCS engine is UB. The actual application is still PPC. However, it runs very well still on my Core 2 Duo MacBook Pro. The engine makes up for any lag from the actual application running under Rosetta. Honestly it's hardly noticeable that it's not fully Intel native.   
(Version 6.1.5)

JONLINK  I love sigma chess, but when I saw there was a new version I was hoping it would be universal. I'll take it anyway I can get it, but it would be nice.

Regardless, a huge thanks to the developer!

This is a great free chess game, I love that I can set the game to various level and that I can import pgn games.  
(Version 6.1.4)

MALCOLM  Sigma Chess and Chessmaster 9000 are two different Chess Products. So there is no comparison.

I use the licensed product of Sigma Chess.

The licensed product allows you to have unlimited PGN file collections. One of my collections contains 2 1/2 million game.

Sorting: Sigma allows sorting by Player,

White, Black, Tournament, year, and ECO.

HIARCS 9.6 worked fine with 10.3.8.

But with 10.4.1 the product will only run in the free version. (Lower rating). Possibly Apply needs a 10.4.2 bug fix to improve the UCI or Terminal (Darwin) recognition.

Notes: The product, Sigma Chess allows you to enter notes to games. Sigma Chess also allows you to create Opening and Endgame libraries.

Kasparov: Is strictly a playing program.

As is Chessmaster. Although the new

CM 9000 unlike 6000 has a PGN download feature.

Where to find it: To add PGN collections go to Chessgames.com for downloads. Chessville also.

Note that many PGN collections contain errors.  
(Version 6.1.1)

JASON PARSONS  I play Kasparov Chessmate at level 1700 winning half the time and it took me five games to beat Sigma Chess at level 1200. I believe the difference is that Sigma Chess makes fewer human like errors. This is less of a pump for my ego, but winning makes me feel like I played a good game instead of beating a bad opponent.

Doesn't have the coolness factor of Chessmaster on a PC with all of the different theme boards, but solid on all of the features that matter. I'm impressed with resource utilization and not burning CPU like Chessmaster on Mac.  
(Version 6.1.1)

ANONYMOUS  you all should try BIG BANG CHESS its pretty kool,

it has support with ichat, and itunes :^)  
(Version 6.1.1)

THEBRIX  A small correction to the last review - HIARCS does allow its playing strength to be set, from 1200 to 2750 Elo. The option is in a different place to all the other settings: Level | HIARCS 9.6 UCI Rating.

A nice touch is that, as well as a slider allowing the strength to be set as a number, there is also a drop-down box allowing it to be set as a (US) category (Class A-D, Expert, Candidate Master ...).  
(Version 6.1)

THEBRIX  Sigma has always been an excellent application in my experience and now, with the new HIARCS engine, it is a brutal one, although there has been little other change between 6.0 and 6.1 which is probably a good thing as the interface is well done and didn't need fixing. HIARCS is relentless - the games I play with it are generally long but I feel I never have the slightest chance - and I suspect that almost all players will quickly retire hurt and revert to Sigma's own engine when playing it.

That said, the HIARCS engine is superb for analysis, there are a great number of parameters to play with, and support for tablebases (precalculated endgame positions for small numbers of pieces) and UCI (an interface language for plugin chess engines) are Mac firsts; Windows-based chess packages have had such features for a couple of years at least and their absence on MacOS has been noticeable.

Finally, I note that Sigma is one of the cheapest ways of owning the HIARCS engine, which has had rave reviews for years as a particularly "human-like" engine (an opinion I agree with).  
(Version 6.1)

RICHARD FOWELL  The download file has been fixed. It will now open cleanly under OS/X versions less than 10.3. It is a great program - I've used all six different plugin chess engines already!

From the developer, Ole:

"This problem should be fixed now. The download

is now a .dmg file instead of zip. Apparently, the built-in zip in OS X 10.3 was not backwards with earlier versions of OS X.

If this still doesn't work, please send me an e-mail. (1/20/2005, Version: 6.1) "  
(Version 6.1)

ANONYMOUS  This may be a great program but it's a nightmare to install. I've installed dozens of programs without problems, but this? No idea. I follow the install instructions to the letter; I'm then told there is no default application to open Sigma Chess 6.1. It will not allow me to access the HIARCS chess engine. Advice, to me, and the developer to make it easier?   
(Version 6.1)