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Comment by jandrese | Hacker News Reader

The specs on this are kind of weird.

Z80, 1MB memory, 2TB HDD.

Is this some kind of super Z80 clocked at 50+Mhz? I tend to think of Z80 systems as having 32-128kB of memory and 400k floppies for storage.

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Z80s are still found in embedded systems, sometimes even in consumer electronics; these, for example, are based on a SoC with a Z80 core at (software-configurable) 24~60MHz, a few hundred KB of bankswitched RAM, and up to several GB of flash storage:

https://en.wikipedia.org/wiki/S1_MP3_player

2TB disk? If you use a real Z80, you can probably run that in append-only mode for the rest of your life. Writing full time at 100kB/s would produce about 9GB/day, filling up that disk in about 6 years. Producing and writing 100kB/s isn’t realistic for a Z80 at <10MHz, though (10 cycles/byte seems to be the best for memcpy, and you would need to generate data, and drive that disk, too. See https://retrocomputing.stackexchange.com/questions/4744/how-...)

I think it means 1024 kB of addressable virtual memory.

The Amstrad CPC had 64K or 128K of RAM + 32K of ROM (in a total addressable space of 64K) using "RAM banking". The Amstrad PCW was the same but with even more RAM (up to 512K). This worked very differently from what we now think of as virtual memory.

On the CPC it worked as follows: There were two 16K ROMs, located at 0-16K and 48K-64K. The 16K-48K middle area contained 32K of fixed RAM.

The upper and lower ROM areas were shadowed by RAM. By writing to an IO port you could switch in either the ROM or a 16K bank of RAM individually into each of those two 16K areas. There was an elaborate system of trampolines to allow the ROM functions to be called, or for the ROMs to read/write to the bank of RAM "hidden" under them.

Edit: https://news.ycombinator.com/item?id=16079674 explains how RAM banking works in Symbos.

Indeed, you could plug extra RAM in the back of the CPC, and even stack these.

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