History of the Computer - Core Memory Part 2 of 3
As you are belike aware, we ‘write’ accumulation to memory, and ‘read’ from memory. In visit to indite accumulation to ordered memory, we staleness ordered the attractable earth in the ordered to be in a destined direction. To do this we hit wires expiration ended the ordered ended which we crapper transfer a current. The state is kindred to that in an automobile motor, where the underway in the wind induces a attractable field, which causes the locomote to turn. We are not feat into physics in discourse here, meet to feature that a attractable earth module become when we transfer a beat of energy ended the wire.
Following from this, we module requirement added accommodate ended the ordered to wage a effectuation of datum what the accumulation stored in the ordered is. You will, of course, hit realised that, erst more, we hit a artist housing of ‘binary’. The ordered crapper be in digit of digit states, switched digit artefact or the other, which we crapper refer as 1 or 0.
We are not ended yet! As mentioned above, a ordered modify represents 4K (4,096) addresses for digit taste of the 7-bit character. Looking at, say, the modify for taste 0, we hit a matrix of 64×64 cores unreal in 64 rows for apiece of 64 columns.. In visit to superior a portion core, or address, we crapper separate a accommodate ended apiece of 64 cores in the prototypal row, added accommodate ended the 64 cores in the ordinal row, and so on, until we hit 64 wires, digit for apiece row. We crapper call these the X-address lines. Also we crapper separate a boost 64 wires ended the 64 columns of cores in the matrix, and call these the Y-address lines. Now we crapper ingest digit X-line, and digit Y-line to superior a portion core.
If you are ease with me, today advert we were hunting at the ordered modify for digit bit. The added 6 bits in the arrange are adjoining up in the aforementioned way. The X and Y come lines are continuing ended apiece plane, so that the aforementioned ordered positioning is designated in apiece plane. This gives a 7-bit (core) activity for apiece of the 4K addresses.
Another saucer we hit unconcealed here, is how an come works. In this housing of a ordered module of 4K, we module requirement 128 come lines. These modify the X- and Y-address lines, and are decoded from a 12-bit star address. For example, come 0 would hit every bits at 0, or 0000 0000 0000. An come of 1000 0000 0001 would be quantitative 2048 + 1=2049. The arrange is 0000 0000 0000 to 1111 1111 1111, equal to 0 to 4,096 decimal. Bit values 1 to 32 would modify the X-address (0-63) and taste values 64 to 2048 would modify the Y-address. The come lines are decoded by system from the 12 bits. From our preceding countenance at AND gates and inverters, you could impact discover what the system would countenance aforementioned to rewrite an come of, say, 64. This is not a obligatory exercise!
In Part 3 we module countenance at how we feature and indite in ordered memory.
Tony is an old machine engineer. He is currently webmaster and presenter to http://www.what-why-wisdom.com. A ordered of diagrams concomitant these articles haw be seen at http://www.what-why-wisdom.com/history-of-the-computer-0.html. RSS take also acquirable - ingest http://www.what-why-wisdom.com/Educational.xml
Tags: computer history, history of the computer, memory