PHost - Differences between HOST and PHost

PHost 4.1h



This document lists the known differences in operation and functionality between PHost and HOST 3.2x. Some of these differences are matters in which, at the time PHost was initially written, the original HOST implementation was unknown and could not be determined by comparing input with results. In these instances, PHost has implemented similar functionality, but does not necessarily duplicate HOST results. Today, most of HOST's inner workings are known, so some of these differences may seem easy to "fix", but that would be counter-productive. The PHost rule set is well-established besides the HOST rules, and changing it would only make matters worse ("what are the alchemy rules of the day?").

These days, HOST doesn't get many updates, therefore it's PHost which keeps trying new rules, which - of course - differ from HOST. Some of the changes are also considered bugfixes in the original implementation.

The differences are grouped according to who is affected, the host or the player. Differences are grouped by the area of the game in which you will encounter it.

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Playing Differences


Formulas & Rounding: Several processes involve rounding. PHost's rounding behaviour often differs from HOST's, so identical formulas might yield different results. At some places, PHost also uses slightly different formulas. The Formulas collection attempts to document PHost's exact behaviour.

Mission Ordering: HOST's mission ordering was not completely known by the time PHost was initially written. Therefore, there are some differences. PHost's mission ordering is described in detail on the Host Order page. The most prominent known differences:

  • In PHost, mine decay happens before all other minefield actions, in HOST, it happens afterwards. PHost should therefore be played with slightly larger values for WebMineSweepRange than HOST.
  • In PHost, sensor sweeping happens after movement. In HOST, it happens in the very beginning.

Messages: PHost condenses most scanner reports. You'll receive only one summary report for each minefield, planet or wormhole scanned. When the messages contain distances, PHost reports a dummy value ("999 ly"). Some messages include slightly more information than in HOST.

Configuration: PHost has many configuration options which can be used to customize many details of the game. Many options which are global in HOST can be set to different values for every player in PHost.

Friendly Code Matching: Special friendly codes never match in PHost. See Friendly Codes. In HOST, only few friendly codes (NTP, mkt, lfm, ATT, NUK) are excempt from matching in combat, and no exceptions apply in other cases (e.g. for movement through minefields).


Combat is different. Period. Attempts have been made to emulate the original combat mechanics as close as possible, but to expect identical results is unrealistic.

PVCR Program: The VCR program must be able to re-play battles according to the same algorithm as the host program. Therefore, to play PHost combat, the VCR program must be replaced by one which knows the PHost combat code. The HOST combat algorithm was not publicly known when PHost was initially written, so PHost simply had to invent its own. For instructions how to install PVCR, see First time with PHost.

Tunable Knobs & Alternate Combat: The PHost VCR program is configurable. Alternate Combat provides a rather different weapon hit model.

Combat Order: Combat order is slightly different than in HOST. The complete rules are documented in the Order of Battle section. The main differences are:

  • in HOST, planets always fight after ships (there are two phases of combat: ship/ship and ship/planet), whereas they are part of the normal battle order in PHost. In particular, when planets are aggressive (ATT, NUK), they often fight first in PHost.
  • PHost distinguishes between aggressor and opponent, HOST does not.
  • PHost since v3.4b respects battle order for intercept attack. Previous versions used reverse Id order, like HOST.
  • in HOST, ships must decloak at once when they reach the DamageLevelForCloakFail. In PHost up to version 4.0i, they would stay cloaked for the whole combat phase, and could even supply-repair to stay cloaked.

Planets: In PHost, planets can capture ships by killing off their crew. In HOST, planets can only destroy ships. This aspect of the game design was actually intended for inclusion in the original HOST program. As it would have required patching vcr.exe and distributing a new copy to all players, this change was judged too great to implement in HOST.

Planets that take damage in combat will remember that damage for the next fight. In HOST, they'll continue with reduced defense, but without damage. Effectively, HOST performs a planet's damage limitations after every fight, whereas PHost performs them only once per turn.

Lizards: In HOST, Lizard ships can be damaged up to 150%. In PHost, every ship which ends a turn with 100% damage or more is destroyed. It is still allowed to reach 150% damage during movement through mines, or during combat.

It can be argued that HOST's behavior is a bug (what does it mean to have more than 100% damage?). In any case, PHost compensates for this difference by making the damage-limited ship speed and shield level formulas relative to 150% damage rather than 100% (see the Formulas page for more details). This gives the Lizard player a slight advantage to compensate for the disadvantage of not having ships with greater than 100% damage survive.

The same reasoning holds for planets. Lizard planets are allowed to suffer up to 150% damage in battle but will explode (be conquered) if they end a battle with more than 100% damage.

Damaged Ships: Since PHost supports ships with more than 10 weapons of a type, the damage limit formulas have been changed to support that. In HOST, a ship with 50% damage can use at most 5 weapons. In PHost, a ship with 50% damage can use half of its maximum set of weapons.


PHost implements alliances in a completely different way than HOST. PHost's alliance feature predates that of HOST by about two years.

Most recent HOSTs implement two alliance levels, "ff" and "FF". "ff" allies roughly correspond to PHost's planet, combat and minefield levels, "FF" corresponds to an additional vision level.

Ship Building

PHost 4 supports up to 999 ships, as do some versions of HOST. Most games still use the old 500-ships limit, though.

Build Queue: PHost implements a Build Queue for which can be operated in three different modes. HOST has a simple round-robin queue with priority builds.

Cloning: In HOST, cloning becomes virtually impossible after the ship limit. In PHost, clone orders are normal ship build orders which walk the build queue like everyone else.

In HOST, there are some restrictions to cloning: you can't clone a ship you are towing, and you can't clone when there's a loaded Firecloud at the base. No such restrictions exist in PHost. Newer HOST versions also relax these restrictions again.

In HOST, you can build and clone at the same time when you have more than 20 PBPs. PHost has an inherent limit of one ship per turn and base.

Build Points: PHost's build point system differs from HOST's PBPs. The PBP queue works similar to HOST's PBPs, but not identical. One major difference is that HOST's build points do not kick in until there are less than 50 slots free, PHost's build points are always available. In return, HOST forces you to do a priority build when you have the most PBPs, PHost does not.

Parts in Storage: The dmp friendly code will not cancel a build order, and will not recycle parts required for the ship build. When a starbase has a pending build order, PHost will not allow Super Refit to use these parts either.

Canceling Build Orders: When you are using a Maketurn program which supports it, PHost allows you to cancel build orders after the ship limit has been reached. All Maketurn programs known to support this feature are listed in this FAQ entry. With HOST, the dmp friendly code is used to cancel build orders and recycle parts in starbase storage.

Ship Movement

Fuel usage: With the standard configuration, fuel usage comes close to HOST's, but is not identical. PHost also offers an additional fuel consumption model (UseAccurateFuelModel) which accounts for the fact that ships get lighter by burning fuel, therefore they consume less fuel. See Fuel Usage formulas.

Zero-Fuel Movement: In PHost, ships without fuel can move at most one light year. In HOST, they can move as far as they get.

Movement through Mines: When the tower runs on a mine and explodes, the towed ship can escape and use the remaining time for moving towards its original waypoint if TowedShipsBreakFree is enabled.

The value of HullTechNotSlowedByMines determines what happens to ships which get damaged in a minefield. The mine hit odds can differ for each warp speed (MineOddsWarpBonusX100 etc.)

Gravity Wells: It is not entirely clear from HOST documentation when and how gravity wells affect ships. In PHost, the conditions are configurable (AllowGravityWells, AllowHyperjumpGravWells). The conditions for gravity wells, and their effect, are documented under Gravity Well formulas.

Intercept: HOST restricts intercept to ships closer than 200 ly, to prevent blind intercepts. PHost allows you to intercept everything you see through your result file (and only that).

PHost implements intercept in a different way than HOST. With circular intercept, the meeting point and movement path of the ships will differ. It shall be noted that HOST's intercept resolution has changed significantly between versions as well.

Ship Missions

Towing: There are two towing models available in PHost. The AllowAlternativeTowing option chooses which one to use. The towing model decided under which condition a ship can tow another one which might not want to be towed.

Towing Cloaked Ships: In HOST, cloaking does not break a tow. In PHost, this can be configured with the AllowTowCloakedShips option.

The HOST behavior rationale is that allies should be able to tow each other's cloaked ships into combat. Unfortunately, it has the side effect of giving cloaking races little defense against the Privateers, since even if a towed ship cloaks, it will never escape the tow of a ship with gravitonic accelerators. A cheap Privateer gunboat can tow a cloaked ship to a starbase and just wait for its fuel to run out (due to cloak fuel burn) or its cloak to fail. The towed ship cannot escape.

PHost enables allies to tow each other's cloaked ships into combat, simply by having the allies give each other the Ship Level of alliance. Thus, there is really no need for non-allies to be able to tow cloaked ships, and the cloaking races can once again escape Privateer tows by cloaking. Thus, it is recommended that AllowTowCloakedShips be disabled.

Super Refit: Super Refit will not use parts which are allocated for a ship build order.

Colonization: When you scrap a ship using Colonize, you'll receive the minerals used to build the ship (multiplied by the RecycleRate), but no money. This differs somewhat from the HOST calculation. In particular, you'll not receive supplies for torps/fighters (i.e. the trick known as "Reverse Alchemy" does not work in PHost).

Pillage: When a ship pillages a planet in HOST, all other Klingon ships in orbit of the same planet will try to gather cash and supplies. Actually, it can even happen that the ship doing the Pillage will not get anything because it is preceded by many empty freighters. In PHost, only the ship with the Pillage mission will get the cash. It must be that way because otherwise Pillage would be pointless in a game with many Klingon players (PlayerSpecialMission configuration option). The CumulativePillaging option can compensate this difference a little and allow many ships to pillage and get stuff (but it will also let them all do damage).

HOST does an additional supply-repair stage after pillaging. PHost does not do that, thus ships cannot repair themselves using supplies gathered by Pillage.


Amorphs: Historically, PHost uses a different formula for Amorphous' colonist breakfast.

Unowned Planets: Even if a planet has mines and factories, these will not produce stuff when there are no colonists to operate them (i.e. the planet is unowned). Since there are not tax collectors, native taxes will be reset to 0. Natural processes like Trans-Uranium Decay and meteorites will still happen.

Overpopulation: Overpopulation is handled differently in PHost and HOST. The permitted population on each planet is computed differently, as are supplies eaten and climate deaths.

Meteor Effects: The exact happiness and population effects caused by a meteor in HOST are not known, so PHost has its own ranges.

New Natives: The exact ranges and probabilities for new natives in HOST are not known. PHost 4.0 has these configurable.

Siliconoids: In HOST, Siliconoid natives like it hot, like Crystals. In PHost, this is version-dependent:

  • up to 3.3b: Siliconoids are treated like all other native races.
  • 3.3c and later: when CrystalsPreferDeserts is on, Siliconoids like it hot. However, Siliconoid growth does not use the CrystalSinTempBehavior option.


Recycling: Recycling parts with the dmp friendly code will not cancel the build order in PHost.

Hulls Recycled: When a base is destroyed during combat or because the planet becomes unowned, all hulls are destroyed along with the base. When a base is given away or conquered in ground combat, hulls are recycled normally.

Tech Downgrades: When HOST downgrades a starbase because the player is unregistered, it will return the money. PHost does not return the money to prevent people from trading Tech for cash.


PHost supports up to 10000 minefields in a game. In HOST (and PHost up to 3.2), the limit is 500. Most games still use PHost with a limit of 500, though, as client support for 10000 minefields is not widely available.

Mine Decay: In PHost, Mine Decay happens before mine sweeping. Therefore, the minefield will be smaller than displayed by your client (and possibly out of range) when you try to sweep it. On the other hand, HOST will report different sizes for a minefield which is laid and then scanned. To compensate this difference, PHost is generally played with a bit larger MineSweepRange.

Minefield Explosions: Depending on PHost version and configuration, handling of overlapping minefields differs.

  • In PHost 4.0b/3.4f and later, overlapping minefields detonate simultaneously, no matter how the overlap was produced. This is similar to HOST's behaviour, although we use better (and more fair) formulas.
  • In older PHost versions, overlapping minefields only explode when they're laid or enlarged, using one of the mine laying ship missions. When two minefields become hostile after being laid (by cancellation of an alliance, maybe), they'll not explode.

It is possible to configure mixtures of the old and new behaviour, see AlternativeMinesDestroyMines.

Mine Laying: In PHost, it is impossible to lay a new mine field when you already are inside one of your mines (except by laying in a different identity, of course). HOST has some tricks which allow that. When inside multiple mine fields, PHost allows you to choose which one to enlarge. By default, PHost adds mines to the lowest-Id minefield you're in.

Mine Laying Order: HOST as well as PHost 3.2 and below do mine laying in order of ship Ids. When all 500 minefield slots are used up, only low-Id ships will be able to lay mines. PHost 3.3 and later use a more fair order (see the Mine Laying mission for details).

Mine Scooping: Mine scooping needs beams in PHost. In HOST, it does not.

Web Mines: HOST has a bit trouble with Web mines that do not belong to the Crystals. Since most of these effects are considered to be bugs, PHost implements that in the "intuitive" way.

The basic rule is that web mines are not different from ordinary mines. Web mine draining, however, is a Crystal-only racial ability. The owner of a minefield (or web mine) is immune to its effects, while others are not (unless they are allies). Therefore, a Crystal ship will have fuel drained from it if it is in a web mine belonging to another Crystal player (in a custom PlayerRace game, for example).

Non-Crystalline webs still have the improved hit odds, and fuel drain when an enemy hits a mine.

Web mines interact with normal mines only when AllowMinesDestroyWebs is enabled.

==> Note that some clients have trouble displaying non-crystalline webs, because the Winplan RST file format does not allow storing those. Clients that evaluate util.dat should display them correctly.


Experience: Experience is treated way different in HOST and PHost.

Ion Storms: Ion storms behave similar to those in HOST, but differ in details. Especially ship effects are computed differently, mainly because of the different implementation of experience.

Glory Devices: glory devices need fuel to explode in PHost. HOST does not require fuel (but was originally documented to do so).

New Features

Wormholes: PHost supports wormholes. HOST needs an external add-on for that.

Wraparound Map: PHost implements a wraparound map in its core, supporting all features across borders smoothly. HOST needs an external add-on for that. With the most popular one, Sphere, things like Sensor Sweep will not work across the border. There is a rather new add-on, Zeus, which claims to support seamless missions across the map borders for HOST.

Remote Control: In PHost, players can take control over each other's ships.

Player/Race assignments: In PHost, every player can be assigned every race. There also exists a HOST version which does that (SRACE), but it doesn't seem to be up-to-date. PHost also has ways to define completely new races.

UTILx.DAT: PHost writes utility data files which can be used by client-side programs. HOST does not, so clients have to rely on message scanning.

Language support: In PHost, every player can choose his language for messages he receives. HOST allows only to replace the language file for all players at once. This HOST feature is rarely used because it breaks message scanning.

Command messages: Some functions of PHost are accessed using command messages. A command message is a normal sub-space message addressed to yourself. HOST does not treat such messages specially. In addition to controlling new PHost functionality, command messages are also used to extend ships' cargo transfer abilities (beamup, transfer, unload).

Giving away Planets: PHost lets you give away planets as well as ships. In HOST, you can only give away ships.

Ship Functions: PHost has a set of new ship functions not available elsewhere. The functions can be freely assigned to ships and ship classes, and restricted to specific players or crew experience levels.

Unsupported Features

DeleteOldMessages: PHost does not keep old messages. There are no plans to support this feature.

'con' and 'noc' Friendly Codes: When asked for its configuration using the con friendly code, PHost does not respond with messages. Instead, it will include pconfig.src in your util.dat, as a file transfer record. Since PHost never sends its configuration when not asked to, the "noc" friendly code has no effect.

VPA Extra Features: HOST 3.22.036 has a switch "VPA Extra Features" which permits some actions not doable with planets.exe or older Winplan. This switch is not implemented in PHost, see AllowVPAFeatures for details.

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Hosting Differences

Configuration: PHost does not come with a "HConfig" program. Instead, PHost uses the plain-text file pconfig.src (and shiplist.txt) to define game parameters. Using the PControl feature, you can run add-ons at any place in the host sequence.

Data Files: PHost uses mostly the same file formats as HOST. It does not use all files HOST uses, and it uses some other ones. See the Technical Information page for more information.

AUXBATT.INI: PHost does not explicitly support the auxbatt.ini hook of HOST (this hook was present in older HOST versions, and went away without notice later). It does, however, support fine-grained hosting control which easily allows you to add it.

TacCom support: PHost does not support the sharing of alliance data in TRN files via the TacCom program. If PHost encounters a TRN file with alliance data in it (using the so-called "leech" method) then it will indicate that the TRN file is corrupt. There have been no requests so far to support TacCom, therefore there are no plans to add it.

Invocation: PHost supports a number of command line options which modify the behaviour. In particular, PHost can check TRN files for errors without actually doing a host run.

Compatibility: PHost is intended to be compatible to HOST, but can of course not be 100% identical. Some incompatible programs are listed in this FAQ entry.

Tim Continuum: When PHost detects that two players illegally share a registration number, their empire will stop working for a turn (ships do not move, planets do not produce). This makes it easier to continue the game or re-host the turn after a Tim Continuum incident, because players do not get information they should not have (as it is the case in HOST which throws ships to random places). These days, most such incidents happen by accident, not by intention. In addition, PHost doesn't punish players for Red status TRNs. It just ignores the offending TRN files and continues as if the player had not submitted a turn file at all.

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Last updated 31 May 2015.

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