the different virtual-hardware modes
VMX-file parameters

I guess this will never make it into the VMware-docs so be very careful. Don't blame me for any unexpected results - you have been warned.

If the usage of any of these settings suddenly cures your Athma - consider making a donation.

Current virtual Hardware

config.version = "8"
virtualHW.version = "4"

This are the entries all recent VMware-versions use. Rumours say that ESX 3 will use them as well.
When ever possible use these settings as they offer the best optimization for current - modern guests.

Legacy virtual Hardware

config.version = "7"
virtualHW.version = "3"

or - depending on the virtual devices

config.version = "7"
virtualHW.version = "4"

Workstation 5 used this settings for it's legacy mode and allowed to create VMs in this mode.
Current VMserver already comes without this GUI-option and I expect that this mode will
disappear as soon as it is no longer needed for ESX.

Useing this mode has some limits: you can no longer use the snapshot-manager!

This does not mean that you can no longer use or create snapshots - it only means that current versions will not offer
snapshots via the graphical interface.
If you know how to create and manage snapshots you can of course use them.

Even in this mode you can have multiple snapshots and clones - the limiting factor is your skills - not VMware in itself.

Don't use this mode unless you really need it - you will loose the benefits of all performance tweaks that come with the current-mode.

Don't use this mode when you need VMware support.

Grandpa-mode

I discovered this when I wanted to create a very small IDE-disk with unusual disk-geometry.

The following seems to apply to current server only - VMplayer doesn't like config-version 6 but is happy with 8.

Warning: I have not seen any docs that say that this can be done.
A normal VM will not power on with this settings before you have upgraded the virtual Hardware.

Warning: Do not use this in production - this is experimental

Warning: If you never use the term "play with VMware" stop reading here.

config.version = "6"
virtualHW.allowVeryOldVersion = "TRUE"

What happens:

this is a major change in the VM.
At the moment I am aware of two aspects that can completely change the behaviour and the virtual Hardware of a given VM.
Be very careful ...

Grandpa-mode Snapshots

A VM in grandpa-mode can use snapshots like in the good old days when REDO-logs also used the name REDO-log.

After you powerdown a VM it will ask you "Revert, Append or Discard?" in case you used also

ide0:0.mode = "undoable"

for your disks.

If you are useing VMware as a tool to survive the internet you can use a layout like this for new guests:

first disk: non-persistent mode

second disk: undoable mode
third disk: persistent mode

Use the first disk to have a "clean on reset" basic installation, configure disk two for your users home directory and handle it as "discard when it looks suspicious" and use the third disk for your downloads and documents.

You think this is a cool way to improve things like the browser appliance? - you got it.
I am posting this in "Feature Requests" since the days of early Workstation 4 (4460) - only comment I ever heard was "we haven't thought of that kind of usage".

Can't I do this with current Workstation? - Well , yes you can do that, but ..... you must be a very advanced user.

The screenshot shows VMserver running in "grandpa-mode"

Grandpa-mode Disks

A VM in grandpa-mode can create and use Cow-disks.

Grandpa-mode IDE-controller

A current VM allows creation of virtual disks larger than 100Mb only.
IDE-disks are created as *x16x63 C-H-S geometry.

The 100Mb limit only applies to disk-creation - disks smaller than 100Mb can be used.
Even for very small disks the VM uses the *x16x63 geometry.
If you want to run very old guests like DOS 3 or older this geometry of the latest fashion might puzzle your guests.

config.version = "6"
virtualHW.allowVeryOldVersion = "TRUE"
ide0:0.dmaCapable = "false"
ide0:0.forcelba48 = "false"

Here is a sample disk to test this:

# Disk DescriptorFile
version=1
CID=7700ecc3
parentCID=ffffffff
createType="monolithicFlat"

# Extent description
RW 32240 FLAT "16mb-flat.vmdk" 0

# The Disk Data Base
#DDB

ddb.virtualHWVersion = "4"
ddb.geometry.cylinders = "248"
ddb.geometry.heads = "5"
ddb.geometry.sectors = "26"
ddb.adapterType = "ide"

Create it with contig.exe

Contig.exe -v -n 16mb-flat.vmdk 16506880

and use DOS-based aefdisk to initialize the disk:

aefdisk /noebios /mbr

VMware Server detects this as you can see in this line - taken from the vmware.log

DISK: OPEN 'e:\dos-old\16mb.vmdk' Geo (248/5/26) BIOS Geo (248/5/26) freeSpace=24500Mb

Do you need a disk with strange layout?
Tell me - I'd like to try this with more variants ...

A very interesting thread in community can be found here:
http://www.vmware.com/community/thread.jspa?messageID=398415