![]() The number of services and apps has increased, and staff members routinely install and use them without involving the IT group. What is the most prevalent form of shadow IT?Ĭloud services, especially SaaS, have become the biggest category of shadow IT. Cloud services: including software as a service (SaaS), infrastructure as a service (IaaS), and platform as a service (PaaS).Hardware: servers, PCs, laptops, tablets, and smartphones.Shadow IT includes all forms of IT-related activities and purchases that the IT department isn’t involved in. Once you understand the concept, it is very simple, so maybe few people bother to write about it.What are the different aspects of shadow IT? You might find more information by using the term "mirror" instead of "shadow", or then again, you might not. This leaves room for them to add more RAM, ROM or peripherals in that space in the future, which would break the mirroring. The official documentation for the system would probably tell you not to use addresses above 0x7FFF. Byte 0 of chip 1 is intended to be accessed at address 0x0000, but you can also access it at address 0x8000. The only difference is the 16th address pin, which is not connected to anything. The address space which this arrangement forms, looks like this: +-+ 0xFFFFīecause the 16th address pin is not connected, addresses 0x8000 and 0x0000 (for example) act exactly the same on the hardware level. The 16th address pin on the CPU is not connected to anything, because it is not minimally required to make the system work with two 16k RAM chips. You also connect it to a NOT gate and you connect the output of the NOT gate to the other RAM chip's chip-select pin. You take the 15th address pin from the CPU and connect it to one RAM chip's chip-select pin. ![]() You connect those directly between both chips and the CPU. How do you connect them together?Įach chip has 14 address pins. Suppose you have a 16-bit CPU (65536 bytes of address space) and you have 2 16kB (16384-byte) RAM chips (and nothing else). This meant the same registers were repeated in memory, which is what an address shadow or mirror is.Ĭould someone expand on or correct this definition, because web searches have not turned up much fruitful information. The SCC READ chip had addresses from 90000 to A0000, but it only had 4 or 5 registers. The example my professor gave is of the original Apple Macintosh. What I understand address shadows to be are addresses which will point to the same place in memory as another, but only because we are decoding the address as little as possible. Now I'm not sure what this means, I'm repeating my lecturer. This approach allows for 'address shadows'. 0x0000 to 0x7FFF is the range of RAM in the address space).Īddresses can be decoded as little as possible, that is, the minimum number of bits in the address are checked to determine the chip select signal, the signal which determines which chip to access. I understand that memory addresses are decoded to find if they point to the RAM, ROM, or I/O, by way of the address (in the example of BBC Micro) being in the RAM range, user ROM range or OS ROM range (e.g. In my uni lecture, I am covering address decoding.
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