Well 4.0 isn't a total rewrite. Seeing that it does not come with a load of app updates, you can downgrade back to the previous version and with 296MB it is not considerably larger than previous firmwares.
Current apps are much larger than they should be. The DLNA/Media player is a temporary
without DRM and uses 690 MB when, if it is using the PS4 OS stack should be MUCH less. DLNA is about 2 MB and VLC is 28 MB and contains everything for streaming over the home network. So these current PS4 apps can run on any OS version as they are almost totally self contained.
DLNA is also a routine that should be able to be called from network standby like my Sony Receiver can and Vidipath requires. Vidipath (DLNA with DRM) requires HDCP 2.2 to support Playready ND (DTCP-IP for 1080P and higher media and several DLNA modes allow a phone running a DLNA APP to control the DLNA/Vidipath player including volume.
No TMP 2.0 so no HDCP 2.2 thus no Playready ND thus no DLNA for commercial Media = the current temporary DLNA media player we now have. This applies to all features of the PS4 that require security like firmware updates.
HDCP is essentially applying a number stream to the data using Xor logic. The numbers are generated by a key and a AES-128 hardware accelerator in the TEE. Neither operation is CPU intensive. HDCP 2.2 is primarily about the negotiation and security of the KEYs and TMP 2.0 about the hardware security supporting the routines used for HDCP 2.2. (Trusted boot - TEE)
http://n4g.com/news/1394790/ps4-consumes-70w-while-downloading-in-standby-because-it-uses-the-main-apu-and-not-just-the-arm-chip said:
Ito-san explained that initially Sony attempted to have background download performed exclusively by the secondary sub-system ARM chip (as it was announced during the consoles presentation in February), in order to keep the main APU powered down, but that proved not to be fully possible.
The download process is too heavy for the ARM chip alone, so the Jaguar-based CPU of the main APU (Accelerated Processing Unit, that includes CPU and GPU) is called into action to do the heavy lifting and protocol processing.
I have several issues with this statement:
1) The entire PS4 hardware went through testing using FPGA hardware before tapeout. It was announced as a coming feature at the Launch presentation. If it slipped by testing before tapeout, it wasn't tested before the launch announcement when developers had hardware using the final version of the PS4 for months?????
2) ARM phones supported HDCP 2.2 in 2012 on batteries for Miracast which means they can stream Playready encrypted media from a cloud server, unencrypt it then encrypt it using HDCP 2.2 for Miracast WiFi to a TV or STB REALTIME.
3) Cerney said the Southbridge has a always running ARM processor primarily for Network standby but the PS4 pulls slightly more than 6 watts in Standby when other STBs with network standby use 500 mw. The PS4 is going to support Vidipath which means it needs to support DLNA with network standby and at 20 watt power levels with full screen video APU off.
4) Firmware updates do not need to be realtime so there is no performance issue and since all data and media goes through Southbridge in any case, the statement that the download process is too heavy for Southbridge does not make sense.
5) A Trustzone TEE contains cryptographic accelerators and can handle real time video decryption including that needed for Blu-ray (AACS) decryption and HDCP encryption at the same time!
6) The 2015 PS4 has a new Southbridge and still no background download.
Cerney: "So that allows background downloads to happen in a very low power scenario."
Ito: "The download process is too heavy for the ARM chip alone, so the Jaguar-based CPU is called into action to do the heavy lifting and protocol processing. While this is the situation with the present design,
Ito-san specified that it could change with further iterations of the consoles design."