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Add You - History of the Computer - Core Memory Part 2 of 3
Shoes, more than any other article of clothing, have really come a long way in the past century. 100 years ago, most people, men and women alike, had just one or maybe two pair of shoes- day shoes for work and night shoes for anything else.In 2006, even the most modest of men probably have at least 5 pair. There’s tennis shoes, dress shoes, dress casual shoes, sandals, work boots, hiking boots and more, all just for men. And you would be hard pressed to find a
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As you are probably aware, we 'write' data to memory, and 'read' from memory. In order to write data to core memory, we must set the magnetic field in the core to be in a certain direction. To do this we have wires passing through the core through which we can pass a current. The action is similar to that in an electric motor, where the current in the coil induces a magnetic field, which causes the motor to turn. We are not going into electromagnetism in detail here, just to say that a magnetic field will occur when we pass a pulse of electricity through the wire.
Following from this, we will need another wire through the core to provide a means of reading what the data stored in the core is. You will, of course, have realised that, once more, we have a classic case of 'binary'. The core can be in one of two states, switched one way or the other, which we can identify as 1 or 0.
We are not finished yet! As mentioned above, a core plane represents 4K (4,096) addresses for one bit of the 7-bit character. Looking at, say, the plane for bit 0, we have a matrix of 64x64 cores arranged in 64 rows for each of 64 columns.. In order to select a particular core, or address, we can run a wire through each of 64 cores in the first row, another wire through the 64 cores in the second row, and so on, until we have 64 wires, one for each row. We can call these the X-address lines. Also we can run a further
“Written truth is four-dimensional. If we consult it at the wrong time, or read it at the wrong pace, it is as empty and shapeless as a dress on a hook.” ~ Robert GrudinRobert Grudin, received a PhD in Comparative Literature, and wrote books about the Time and the Art of Living, The Grace of Great Things: Creativity and Innovation, and On Dialogue: An Essay in Free Thought. He well understood our human frailty and helps us to understand how to not be so defens
As you are probably aware, we 'write' data to memory, and 'read' from memory. In order to write data to core memory, we must set the magnetic field in the core to be in a certain direction. To do this we have wires passing through the core through which we can pass a current. The action is similar to that in an electric motor, where the current in the coil induces a magnetic field, which causes the motor to turn. We are not going into electromagnetism in detail here, just to say that a magnetic field will occur when we pass a pulse of electricity through the wire.
Following from this, we will need another wire through the core to provide a means of reading what the data stored in the core is. You will, of course, have realised that, once more, we have a classic case of 'binary'. The core can be in one of two states, switched one way or the other, which we can identify as 1 or 0.
We are not finished yet! As mentioned above, a core plane represents 4K (4,096) addresses for one bit of the 7-bit character. Looking at, say, the plane for bit 0, we have a matrix of 64x64 cores arranged in 64 rows for each of 64 columns.. In order to select a particular core, or address, we can run a wire through each of 64 cores in the first row, another wire through the 64 cores in the second row, and so on, until we have 64 wires, one for each row. We can call these the X-address lines. Also we can run a further
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As you are probably aware, we 'write' data to memory, and 'read' from memory. In order to write data to core memory, we must set the magnetic field in the core to be in a certain direction. To do this we have wires passing through the core through which we can pass a current. The action is similar to that in an electric motor, where the current in the coil induces a magnetic field, which causes the motor to turn. We are not going into electromagnetism in detail here, just to say that a magnetic field will occur when we pass a pulse of electricity through the wire.
Following from this, we will need another wire through the core to provide a means of reading what the data stored in the core is. You will, of course, have realised that, once more, we have a classic case of 'binary'. The core can be in one of two states, switched one way or the other, which we can identify as 1 or 0.
We are not finished yet! As mentioned above, a core plane represents 4K (4,096) addresses for one bit of the 7-bit character. Looking at, say, the plane for bit 0, we have a matrix of 64x64 cores arranged in 64 rows for each of 64 columns.. In order to select a particular core, or address, we can run a wire through each of 64 cores in the first row, another wire through the 64 cores in the second row, and so on, until we have 64 wires, one for each row. We can call these the X-address lines. Also we can run a further
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Following from this, we will need another wire through the core to provide a means of reading what the data stored in the core is. You will, of course, have realised that, once more, we have a classic case of 'binary'. The core can be in one of two states, switched one way or the other, which we can identify as 1 or 0.
We are not finished yet! As mentioned above, a core plane represents 4K (4,096) addresses for one bit of the 7-bit character. Looking at, say, the plane for bit 0, we have a matrix of 64x64 cores arranged in 64 rows for each of 64 columns.. In order to select a particular core, or address, we can run a wire through each of 64 cores in the first row, another wire through the 64 cores in the second row, and so on, until we have 64 wires, one for each row. We can call these the X-address lines. Also we can run a further
Making sure that your search engine makes it as easy as possible for your customers to find what they are looking for is business-critical. It is also very difficult - good search engines can cost an awful lot of money and require a lot of ongoing effort to keep them up to scratch.As an example: on Monday 12th December 2005, I wanted to buy a copy of Jamie Oliver's new cook book Jamie's Italy from amazon.co.uk. So, I went to the "Books" section of their websit
If you are still with me, now remember we were looking at the core plane for one bit. The other 6 bits in the stack are connected up in the same way. The X and Y address lines are continued through each plane, so that the same core location is selected in each plane. This gives a 7-bit (core) selection for each of the 4K addresses.
Another point we have discovered here, is how an address works. In this case of a core memory of 4K, we will need 128 address lines. These form the X- and Y-address lines, and are decoded from a 12-bit binary address. For example, address 0 would have all bits at 0, or 0000 0000 0000. An address of 1000 0000 0001 would be decimal 2048 + 1=2049. The range is 0000 0000 0000 to 1111 1111 1111, equivalent to 0 to 4,096 decimal. Bit values 1 to 32 would form the X-address (0-63) and bit values 64 to 2048 would form the Y-address. The address lines are decoded by logic from the 12 bits. From our previous look at AND gates and inverters, you could work out what the logic would look like to decode an address of, say, 64. This is not a compulsory exercise!
In Part 3 we will look at how we read and write in core memory.
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