If you have been reading the news pages or following the Acorn Games Newsgroup recently, you will be aware of the controversial 'free' Doom port for RISC OS: Doom-It-Yourself by Andreas Dehmel. Unlike previous ports, which R-Comp (the publishers of the commercial release) have been able to quickly silence, DIY is apparently immune to this, as it is distributed in source form, and needs to be compiled. This is in fact easier than it may sound, and we've managed it to bring you the first comparison of it with the commercial release.
 

A key argument for those who are suspicious of DIY is that it is inferior to Acorn Doom, so we've run it through a few arbitrary speed tests (ie. how fast it appears to run) and we'll have actual FPS figures soon to corroborate them. Also, we look at general support, bugs and other related issues.
 

The article has now been updated to take account of the many recent improvements to DIY.
 

Speed

Both are, in general, quite playable on a RiscPC 700 in standard (320x256) resolution, and jerky to a generally unplayable extent at 480x352. All tests were carried out with a Risc PC 700, 8+1MB RAM, and *RmFaster SharedCLibrary.
 
In Ultimate Doom (Doom I) there is a difference in small levels; Acorn Doom shows a definite speed advantage. However, on very large and complex levels, such as in the Thy Flesh Consumed episode, this speed difference is less obvious, and DIY does occasionally show a small advantage.
 

In Doom II, on the early levels, Acorn Doom has a noticeable edge in all resolutions. There is little to tell between the two on larger levels; DIY often has a slight edge there but this is rarely noticable - in general Acorn Doom is the faster.
 

There seems to be some crucial difference between the plotters; Acorn Doom offers a generally more stable refresh, but this means that a very large level produces a more pronounced slowdown than DIY which seems to disregard the complexity of the level. The base plotting speed of Acorn Doom appears to be faster despite this, so a simple level is markedly more responsive.
 

The speed differences are unlikely to be noticable on a StrongARM where the frame rates are very smooth on Acorn Doom already; one would expect a similar increase with DIY, but the current release is not optimised for it, so Acorn Doom is likely to have whatever edge there is. DIY is under constant development however, and we have heard of some updates that markedly increase SA speed and offer a few extra FPS on slower machines.
 
On DIY, the 16-bit mode offers a faster display for simpler scenes than the 8-bit, but the big slowdown (on slower RiscPC's) kicks in for more complex ones.
 

The latest version of DIY, due for release in the week of the 25th May, features a 24-bit mode now very similar in speed to Acorn Doom, even on slow Risc PC's, and with very little slowdown compared to its own 256 colour mode.
 
Additionally, while taking the screenshots below I noticed something very peculiar - Acorn Doom only uses 320x240 in a 320x256 mode, so this could well be the origin of much of its small speed advantage. DIY takes up all the available screen area, so has to plot more of the scene anyway.
 

Some screenshots

These demonstrate some of the visible differences. The Acorn DOOM screenshots are taken in standard (320x240) resolution and the DIY screenshots in 320x256. Both are 24-bit and at gamma correction level 1, with DIY's hardware gamma correction enabled. Click on them to view them in more detail:
 

Acorn DOOM's 'cut down' view of the weapon	DIY Doom showing the whole weapon
The 'cut down' plasma gun of Acorn Doom	DIY DOOM showing the plasma gun in its full glory
Recommend that you look at these two shots at full size to appreciate the difference:
Acorn DOOM's reduced 320x256 mode and distorted invisibility effect	DIY Doom's full transparency in action

• Has no user interface and has to be run from script files
• Needs to be compiled (taking around 20-30 minutes) which can be complex
• Getting hold of the necessary programs to compile it is confusing if you don't have them already
• Has no music
• Controversial; some strange legal restrictions:
   
  R-Comp have secured the sole rights for distribution of executable versions of DOOM for the Acorn (hence the fact that DIY cannot be supplied ready-compiled), and also sole rights for the sale of WAD data to Acorn users, so technically, Acorn users are only legally allowed to buy copies of PC DOOM from R-Comp.
   
  This situation is obviously unworkable, hence general acceptance of DIY DOOM as at least subversively legitimate. More information can be found in one of R-Comp's public statements in the Old News section.

Acorn Doom Pros

• Clean and professional
• User interface allows point-and-click WAD management and vidmode changing
• Easy installation sequence
• The official conversion
• Full MIDI music support
• Multitasks in a window if you have the power
• By a company committed to further releases

DIY Pros

• Full transparency of 'partially invisible' objects in 24-bit mode (R-Comp DOOM uses the original PC distortion effect) - see above
• Numerous built-in extra cheats not found in other versions of DOOM
• NETWORK SUPPORT. DIY can be played over the internet against your friends or over a Local Area Network. This is the only version that supports it.
• Inbuilt DehackED support - instead of actually editing the game executable to produce automatic shotguns, repeating BFG's and imps that fire lost souls, you can just tell DIY to load the patch file at run-time.
• Can be worked on by users, so updates are coming thick and fast from an effectively vast team of programmers
• Completely free (although you must buy the DOOM levels for the PC or download the Shareware levels from ID Software)
• Very stable; once running rarely crashes out, even with very large patch WADs
• Screen drip effect between static screens as on the PC
• The whole weapon is displayed at all times, even when the status bar is visible
• Full variety of colour depths supported: 8-bit (256 colour), 16-bit (32,000 colours) and 24-bit (16 million colours)

Acorn Doom Cons

• Quite unstable with patch WADs, due to many WADs produced on PCs being written badly, which upsets the multitasking and crashes the game. On the plus side, well-written WADs like AliensTC work perfectly.
• No network support (yet), so only single-player games are possible.
• Using Dehacked requires patching executable using third-party application
• Some bugs in frontend
• No major updates appeared as yet
• Screens just flick from one to the other without the drip transition
• The lower quarter of the guns are always missing from the display, even with the status bar obscured - see above
• Costs £30 (although this includes the complete Doom collector pack for the PC and has already dropped £5 from its original sale price).