Ciro Santilli @cirosantilli 34

In this section we will gather some more advanced ideas besides the basic features described at how the website works.

They are pioneers in making superconducting magnets, physicist from the university taking obsolete equipment from the uni to his garage and making a startup kind of situation. This was particularly notable for this time and place.

They became a major supplier for Magnetic resonance imaging applications.

But only for the proper Riemann integral: math.stackexchange.com/questions/2293902/functions-that-are-riemann-integrable-but-not-lebesgue-integrable

Google has put considerable effort into custom hardware to greatly optimize its stack, in a way that is quite notable compared to other tech companies.

www.knfusa.com/en/laboport/ (archive).

As highlighted e.g. at Human Compatible by Stuart J. Russell (2019), this AI alignment intrinsically linked to the idea of utility in economy.

The exact format of table entries is fixed _by the hardware_.

Each page entry can be seen as a struct with many fields.

The page table is then an array of struct.

On this simplified example, the page table entries contain only two fields:so in this example the hardware designers could have chosen the size of the page table to b 21 instead of 32 as we've used so far.

All real page table entries have other fields, notably fields to set pages to read-only for Copy-on-write. This will be explained elsewhere.

It would be impractical to align things at 21 bits since memory is addressable by bytes and not bits. Therefore, even in only 21 bits are needed in this case, hardware designers would probably choose 32 to make access faster, and just reserve bits the remaining bits for later usage. The actual value on x86 is 32 bits.

Here is a screenshot from the Intel manual image "Formats of CR3 and Paging-Structure Entries with 32-Bit Paging" showing the structure of a page table in all its glory: Figure 1. "x86 page entry format".

The fields are explained in the manual just after.

Convert virtual addresses to physical from user space with /proc/<pid>/pagemap and from kernel space with virt_to_phys:

Dump all page tables from userspace with /proc/<pid>/maps and /proc/<pid>/pagemap:

Read and write physical addresses from userspace with /dev/mem:

He does lots of little experiments which is cool.

No research papers but has citations: www.yohei.me/publications which is cool.

The co-founder's name, Toby Cubitt, is the mos awesome thing ever (Cubitt -> qubit). From UCL.

Funding:

Bibliography:

Initially light was though of as a wave because it experienced interference as shown by experiments such as:

But then, some key experiments also start suggesting that light is made up of discrete packets:and in the understanding of the 2020 Standard Model the photon is one of the elementary particles.

This duality is fully described mathematically by quantum electrodynamics, where the photon is modelled as a quantized excitation of the photon field.