Asus P4S800-MX has SoundMax AD1988 Codec, not HDA. It has HWID of both Realtek and SoundMax. So, BSOD Will be always irrespective of correct drivers or not.

For example:
pci\ven_1039&dev_7012&subsys_810D1043 - that is HWID for SoundMax, smwdmSIS.inf file.
pci\ven_1039&dev_7012&subsys_810D1043 - that is HWID for Realtek, alcwdm12.inf and alcxau12.inf files.

Could the problems with drivers for Realtek, Soundmax (blue screen portcls.sys) et al be associated with KB888111 as it seems Microsoft has two versions of this Universal Audio Architecture (UAA) High Definition Audio class driver ?

KB888111 and KB835221

Gigabyte GA-965P-DS4 (Realtek High Definition audio) motherboard requires Microsoft UAA (Universal Audio Architecture) Bus driver package - KB835221 to be loaded before installing the audio function drivers.

Microsoft state that KB888111 only applies to HD Audio known to it prior to August 1, 2004

No.

The problematic drivers are all non-HDA, i.e. AC'97. The problem is JUST the SoundMAX & Sigmatel drivers. They're designed to work only for a very limited range of OEM HWIDs. The consequence is that you have to include EVERY driver out there of either of these brands to support ALL OEM HWIDs.

And FYI: the KB888111 hotfix is an update of the KB835221 hotfix.

KB888111 and KB835221

Gigabyte GA-965P-DS4 (Realtek High Definition audio) motherboard requires Microsoft UAA (Universal Audio Architecture) Bus driver package - KB835221 to be loaded before installing the audio function drivers.

Microsoft state that KB888111 only applies to HD Audio known to it prior to August 1, 2004