doubt memory chip hdd bios

[ÍStef.1]

1) I spoke to a hard drive specialist and he said that the BIOS of 2.5" and 3.5" HDDs is recorded on these memory chips but I don't know what type of memory and retention time
the models:

The 8pins (4 pins on each sides) with 25P05VP、25P10VP、25F512、25F1024、25F1024AN、SST25VF512、SST25VF010, etc. are the BIOS. 

2) Are the firmware and Smart of 2.5" and 3.5" HDDs stored on another chip on the PCB? What type of chip?

[Tesla DeLorean]

It's a data storage device, it puts SMART and bad sector / track / cylinder mapping on the drive media itself. Most current ones will have servo data embedded on the media, either on it's own cylinder, or between them. Older drives tended to fail due to motor, bearing, and heads sticking/crashing on the media.

Current drives also re-write the whole track in a pass, old ones had 512-byte sectors, later 4KB, and now they don't try switching from read/write to overwrite sectors in-place.

Tape drives, the "rubberized" capstans perishing.

Hybrid drives used NAND FLASH.

Serial NOR FLASH devices, I'd expect retention pushing at least 3-4 decades, but clearly a) no one is going to guarantee that, b) technology is a moving target.

EEPROM's can be more problematic, loss of bits at temperature. EPROM's there was grow back of blown fuses.

[ÍStef.1]

1) these models mentioned are (25P05VP, 25P10VP, 25F512, 25F1024, 25F1024AN, SST25VF512, SST25VF010) are all Nor flash or NAND chips?

2) bios, firmware and S.M.A.R.T are all stored on a single chip on the PCB of the 2.3" or 3.5" HDD? Or are they separate chips?

[Tesla DeLorean]

How did you get assigned this task?

Byte readable/writable is going to be NOR arrangement (ie suitable for random access, code execution), larger block access NAND. Higher density, and perhaps multi-level (charge states), with Reed-Solomon type error detection/correction, methods will depend on the geometry.

There are a myriad of ways to store information, which manufacturer did what / when is harder to pin down.

Things running some OS will store primary code on the drive, and load/execute in SDRAM. Or pull from NAND or Serial SPI

[ÍStef.1]

hese models mentioned are (25P05VP, 25P10VP, 25F512, 25F1024, 25F1024AN, SST25VF512, SST25VF010) are all Nor flash or NAND chips?

[ÍStef.1]

bios, firmware and S.M.A.R.T are all stored on a single chip on the PCB of the 2.3" or 3.5" HDD? Or are they separate chips?

[ÍStef.1]

??

[ÍStef.1]

SpiFlash (Serial Nor Flash) used in hdd for store bios firmware can retain data for how many years and at what storage temperature 35C?

[Andrew Neil]

https://community.st.com/t5/other-hardware/doubt-eeprom/m-p/714176/highlight/true#M28490

https://community.st.com/t5/other-hardware/doubt-flash-memory-nor-retention/m-p/711253/highlight/true#M28422

etc, etc, etc, etc, etc, etc, etc, etc, etc, etc, etc, ad nauseam...

[Tesla DeLorean]

Hard to generalize as so many makers and geometry. Evidence would suggest most should be viable for many decades.

The devices, the HDD, are storage devices so code and data can be stored on the media itself. 

Understand no one here is interested in your archival project. For critical data, store it in multiple forms.

The primary storage market is in the here and now, not high criticality long term niche usage. The business boom bust cycles are shorter than the type of commitment you're looking for.