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On 31/08/2015 15:41, Peter Humphrey wrote: |
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> On Monday 31 August 2015 11:42:28 Alan McKinnon wrote: |
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>> On 31/08/2015 10:50, Peter Humphrey wrote: |
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>>> The desktop machine I'm referring to (an Amari "workstation") dates from |
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>>> 2009. It has an i5 processor, 16GB RAM* and two 2GB SSDs as the main |
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>>> power sinks. It sits (runs) in a boxroom 6ft square and keeps it |
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>>> comfortably warm. I haven't noticed any change in ambient temp since the |
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>>> SSDs replaced spinners. |
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>>> |
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>>> * Whoever named that Random Access had a strange understanding of English. |
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>>> The last thing I want from memory is random access! How much better it |
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>>> would have been to call it something like Direct Access. Oh well - much |
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>>> too late now. |
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>> |
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>> It's random access to distinguish it from serial access. In the early |
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>> early days there were a lot of strange methods being tried to build |
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>> memory - like dots on a cathode ray tube! To get to bit you wanted, you |
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>> had to wait till the scanning beam reached that part of the screen - |
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>> serial access. Addressable memory on a grid pattern came much later. |
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> |
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> Yes, of course I know all that, but it's still the antithesis of random - it's |
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> absolutely specific. Random is what you'd get if you didn't specify anything. |
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|
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Ah, an old timer - I forgot that for a second there :-) |
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> My favourite storage medium was core store. Millions of tiny ferrite rings, |
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> each at an intersection of orthogonal X and Y wires to specify the address, |
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> and a write pulse on another wire on the Z axis. At least, that's as close as |
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> I can remember now, 40 years later. No wonder computers were expensive. |
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|
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40 years maybe, but still dead on the money. That's exactly how that |
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memory worked. |
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> |
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> I won't tell you what systems used a 24-bit processor and 12 or 16 KB of 2us |
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> core store backed by a 2MB disk (three feet in diameter), for fear of |
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> frightening you. ;-) |
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Nah, I have some experience with such things. |
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Remember the old horror stories about not smoking in the computer room, |
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because smoke particles are much bigger than fly height of the disk |
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heads? The young 'uns here never had to deal with that. |
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> |
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>> Random Access really means "able to access any random address as fast as |
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>> any other random address". |
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> |
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> My point is simply that the addresses are very far from randomly chosen. The |
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> distinguishing feature of the store is that you can go directly to the |
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> required location, without having to wait for it to reach the read/write |
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> device. |
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|
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We understand each other perfectly; the odd bit is that word "random". |
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We both know it doesn't have the obvious meaning to a modern eye, and we |
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both know what random access really means |
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> |
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> As I said though, there'd be no point in getting all stressed about it now. |
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> |
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>> RAM is also not the opposite of ROM :-) |
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> |
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> I seem to be having a senior moment here; at least, I don't follow that. |
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When I was still a kid learning about memory, many folks thought ROM was |
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very different from RAM, and that somehow ROM didn't have the same |
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random access qualities that RAM has. It does, except that ROM can't be |
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written (and some RAM needs continual refreshing which ROM doesn't, but |
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that's another topic). |
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Eventually I gave up trying to clarify that part. |
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-- |
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Alan McKinnon |
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alan.mckinnon@×××××.com |