09-06-2022, 11:05 AM
Hi Mjelic,
You are correct in that the chip count will be based on capability in many aspects and as Snuffytime pointed out, the use of specialised integrated logic, which in some cases were almost a complete computer in a single chip. Primarily it will be dependent on when in the commercial computing cycle the unit was developed.
All the early Z80 systems use off the shelf logic to keep the development costs down, additionally most of the early systems were hand built. However as the idea of broad home use computers took off, large scale production, chip densities increases and the focus on mass production, the chip count dropped and the capabilities increased, all at the same time.
Focusing on the Microbee, as Snuffytime indicated the Microbee evolved from a S100 based computer into a kit that could be assembled by the home constructor and was initially all off the shelf components, excluding the case and power pack. When these were developed, the 2K Static RAM memory chip was the most economical that was available. As a result to get a 32KB system you needed 16 0.6" chips (quite a lot of real estate), however the advent of cheaper DRAM a few years later meant that twice the memory 64KB could be done in 8 0.3" chips taking up the real estate space of only 4 of the original chips.
Effectively this gave a 8 fold increase in memory density and a 2 fold decrease in chip count.
It was only a few years latter again and further 4 fold increase was seen in the memory capacity with no change of chip count with 256KB of memory in 8 chips taking up the same space that 4 of the original 2K chips, which only gave a total of 8KB.
In fact by this stage it was possible to purchase the SRAM slim 0.3" chips in high density which could achieve the original 32KB in a single chip half the width of the original 2K chip. A 16 fold reduction in chip count and half the board space, of just one of the original chips.
By this point right across the industry, much of the discrete logic was being replaced by either specialty large scale integration of gate into a single chip or Programable logic devices that could take the place of many individual logic components. In the case of the Microbee Programable logic was first introduced with the DRAM Coreboard and then use for the Premium and 256TC releases.
I have seen some imbedded (so no permanent human interface other than a serial terminal connection) Z80 systems from the late eighties with a chip count below 10, these still were using off the shelf components (no LSI chips or programable logic). If these were used I suspect the chip count could be as low as four. Further to that many industrial applications started to use Microcontrollers which effectively was a complete embedded computer in a single chip, CPU, memory (both RAM and mask programmed ROM), I/O control, timing even display and keypad input etc.
Ernest.
You are correct in that the chip count will be based on capability in many aspects and as Snuffytime pointed out, the use of specialised integrated logic, which in some cases were almost a complete computer in a single chip. Primarily it will be dependent on when in the commercial computing cycle the unit was developed.
All the early Z80 systems use off the shelf logic to keep the development costs down, additionally most of the early systems were hand built. However as the idea of broad home use computers took off, large scale production, chip densities increases and the focus on mass production, the chip count dropped and the capabilities increased, all at the same time.
Focusing on the Microbee, as Snuffytime indicated the Microbee evolved from a S100 based computer into a kit that could be assembled by the home constructor and was initially all off the shelf components, excluding the case and power pack. When these were developed, the 2K Static RAM memory chip was the most economical that was available. As a result to get a 32KB system you needed 16 0.6" chips (quite a lot of real estate), however the advent of cheaper DRAM a few years later meant that twice the memory 64KB could be done in 8 0.3" chips taking up the real estate space of only 4 of the original chips.
Effectively this gave a 8 fold increase in memory density and a 2 fold decrease in chip count.
It was only a few years latter again and further 4 fold increase was seen in the memory capacity with no change of chip count with 256KB of memory in 8 chips taking up the same space that 4 of the original 2K chips, which only gave a total of 8KB.
In fact by this stage it was possible to purchase the SRAM slim 0.3" chips in high density which could achieve the original 32KB in a single chip half the width of the original 2K chip. A 16 fold reduction in chip count and half the board space, of just one of the original chips.
By this point right across the industry, much of the discrete logic was being replaced by either specialty large scale integration of gate into a single chip or Programable logic devices that could take the place of many individual logic components. In the case of the Microbee Programable logic was first introduced with the DRAM Coreboard and then use for the Premium and 256TC releases.
I have seen some imbedded (so no permanent human interface other than a serial terminal connection) Z80 systems from the late eighties with a chip count below 10, these still were using off the shelf components (no LSI chips or programable logic). If these were used I suspect the chip count could be as low as four. Further to that many industrial applications started to use Microcontrollers which effectively was a complete embedded computer in a single chip, CPU, memory (both RAM and mask programmed ROM), I/O control, timing even display and keypad input etc.
Ernest.