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43

As noted in some initial comments (but I feel fine answering, as I had the exact same ideas when I read the question), this is a general progression of technology but there are two very specific factors for RAM: Core Memory -> Integrated Circuits While many different, very expensive, systems were used in the first computers, including mercury delay lines, ...


30

I don't know details of the Sharp PC-G830 specifically but the technique used to address more than 64K with a 16-bit address bus is called "bank switching". This involves setting up some portions of memory to be switchable via an I/O port line and then the application program organizes things in memory such that different sections can be switched ...


26

I'm mostly concerned about RAM. Why was it so expensive? It wasn't - at least not once integrated circuit RAM became available in the 1970s. Compared to other chips, RAM was cheaper both per transistor and per package. Some example prices:- From an advert in Byte magazine issue #1 (Sept 1975) 8080 CPU: (4,500 transistors) $149.95 = $33 per thousand ...


15

There are a number of approaches that can allow a CPU with a 16-bit address bus to address more than 64kBytes of memory: Bank Switching - explained in another answer,basicaly switching for example 8- or 16-kBytes blocks back and forth into the addressable range, so in effect exchanging the blocks with ones that are currently paged in. Some computers could ...


14

Didn't people living at that time feel sudden reductions in size/availability as technologies evolved? And if they didn't, why wasn't there a "jump" in memory availability when technology reached a certain state? Yes - except that since it happened on an annual basis, we got used to having jump after jump after jump in technological capability. It ...


8

For the origin of fixed size pages, and independently mapped pages, you need to go back at least as far as the Manchester Atlas machine of 1962. A historical perspective of both the Atlas ad the earlier Mark I can be found here. In that article it mentions that Atlas memory was divided into fixed size pages of 512 words each. The idea of separating virtual ...


7

Another solution worth mentioning — although I doubt it was used by the systems you mention, and it merely allows addressing twice as much as 64K of memory — is "Split I&D", as rather famously used on later models of the PDP-11. A program could have 64K of memory for program text, and 64K of memory for data, for a total of 128K. The processor ...


7

On my windowsill, I've got (roughly) 2K bits of core memory in a picture frame. According to an engineering manager it was assembled by Philippina seamstresses, and they were able to do it for about three years before their eyesight failed. He sounded smug rather than horrified. Each core, representing one bit, has four wires threaded through it. If we ...


5

The brief answer to the question is we watched the evolution of computer technology from computers that filled a room and cannot hold a candle to a watch we can wear on our wrist. You might as well ask why we didn't have cars that could do 200 mph back in 1900. Part of the answer to your question is R&D the other part is paying for that R&D. Remember ...


4

Since the invention of ICs, computer memory size has been gated by Rock's law, or Moore's second law. At any point in time, no one could afford the rapidly growing costs (now many $billions USD) it took to build the more advanced semiconductor fab lines that are required for smaller lithography higher density memories, until the market grew enough, and ...


2

An observation I have made recently is that only things which involve a lot of material have a natural bottom price. A washing machine weighs 100 pounds, a car weighs 2000, a house 200,000 (or whatever). People have to dig coal and ore out of the earth, make steel, fell trees, truck it to processing plants etc. No amount of automation or technological ...


1

There's also the TI-99/4A way of accessing more ROM and RAM than there is address space. The TMS-9900 has a 15 bit address bus and could therefore only address 32768 16 bit words. When one looks at the memory map of the TI-99/4A one can see that the console can address (theoretically) up to 32KiB+256 RAM, 16KiB VRAM, 8KiB + 2x8KiB ROM, 24KiB + 16x40KiB GROM ...


1

For the same reason as: CPUs increasing in frequency from sub-MHz to multi-GHz CPUs increasing in number of cores from a single core to several dozen Hard disk drives increasing in capacity from a few MB to several TB Modems increasing in speed from a few hundred bit/s to gigabits/s Wi-Fi increasing in speed from 2 Mbit/s to gigabits/s Ethernet increasing ...


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