The PCW9512 was launched in 1987 as a replacement for the Amstrad PCW8512. The configuration of the package was changed. The dod-matrix printer was swapped for a daisy-wheel printer, which produced better quality letter documents, but of course did not support graphics. The system however came equipped with a centronix parallel port, that allowed non Amstrad printers to be connected. The PCW9512 came with version 2 of the Locoscript Word Processor, which inluded a spellcheck module and mail merge capabilities. The CRT screen was replaced as well, the green-screen was swapped for a white-on-black type. Besides these changes, the PCW9512 remained functionally similar to the PCW8512.

In 1991 the PCW9512 was replaced by the PCW9256 and the PCW512+. Both of these machines had a standard 3.5" 720KByte double density and double sided disk drive. The machines came with multiple printer options, the standard Amstrad daisy wheel printer, but also a canon inkjet printer for much better quality documents. The PCW9256 was a bit of a reversal, it came with the older dot matrix printer, only 256KByte of RAM and the older Locoscript V1 word processor, making it not much different than the older PCW8256.

CP/M Plus, also known as CP/M 3.0, was the last major 8-bit release of Digital Research’s Control Program for Microcomputers, introduced in 1983. Architecturally, it extended the traditional CP/M design of BIOS, BDOS, and CCP by introducing a bank-switched memory model that allowed systems with more than 64 KB of RAM (commonly 128 KB or more) to take advantage of the extra space. The BDOS was redesigned to reside partly in a common memory bank, while transient programs executed in a separate banked region, giving applications nearly the full 64 KB address space while still preserving the operating system in memory. This scheme enabled larger, more complex programs to run on 8-bit Z80 and 8080-class machines, while maintaining backward compatibility with existing CP/M 2.2 applications.

In addition to expanded memory support, CP/M Plus added advanced system features such as password-protected files, improved file and record locking for multiuser scenarios, and more granular error handling. The BDOS call set was extended to provide enhanced time and date stamping, disk parameterization, and buffered console I/O, improving performance on systems with floppy and Winchester disks. From the user perspective, CP/M Plus included a more sophisticated CCP with command history, aliasing, and the ability to chain commands, making it more interactive than earlier CP/M releases. For developers, its richer API and banking model made it a more capable target for compilers and application suites, bridging the gap between classic 8-bit CP/M environments and the emerging 16-bit world of CP/M-86 and MS-DOS.

The Motorola 6845 CRT Controller (CRTC), later second-sourced by Hitachi (HD6845), Rockwell, and others, was one of the most influential video timing chips of the late 1970s and 1980s. It was not a graphics generator in itself; instead, it produced the precise timing signals needed to drive a raster display, such as horizontal and vertical sync pulses, row and character addresses, and memory fetch cycles. Systems attached external character generators (ROMs) or pixel logic to interpret the memory data, while the 6845 ensured the scanlines appeared in the correct order and at stable refresh rates. Its programmability, registers controlling horizontal total, vertical total, sync widths, cursor position, and so forth, made it adaptable across a wide range of systems, from text terminals to microcomputers.

The 6845’s flexibility came from its ability to map arbitrary chunks of RAM to display regions using start address registers, row address counters, and cursor control. For instance, a designer could allocate just 2 KB of RAM for a 40×25 text screen, or more for bitmapped graphics, with the 6845 providing the address sequencing. Many early microcomputers such as the BBC Micro, Amstrad CPC, and Commodore PET derivatives used the chip, often combining it with a custom video gate array or ULA to generate the pixel stream. IBM also adopted the 6845 in its original Monochrome Display Adapter (MDA) and Color Graphics Adapter (CGA), cementing its influence on the emerging PC standard.

Although by itself the 6845 did not support modern concepts like sprites or hardware scrolling, its register set was exploited creatively. Programmers discovered that by rewriting registers mid-frame (a technique known as “raster tricks”), they could produce split-screen effects, palette changes, or smooth scrolling beyond the documented capabilities. Over time, more integrated graphics controllers absorbed the 6845’s functionality into larger chips that combined timing, pixel generation, and sometimes even acceleration. Nonetheless, the 6845’s architectural model, separating timing control from pixel memory, shaped early video hardware design and left a strong legacy in the personal computer industry.

The 6845s main function is to properly time access to the display memory, and to calculate the memory address of the next portion to be drawn. Other circuitry in the machine then uses the address provided by the 6845 to fetch the pattern and then draw it. The implementation of that hardware is entirely up to the designer and varied widely among machines. The 6845 is intended for character displays, but could also be used for pixel-based graphics, with some clever programming.

Computers that used the 6845 are, among others:

• BBC Micro
• Amstrad CPC
• Videx VideoTerm display cards for Apple II

The Chip is also used in some of the early PC video cards such as the MDA, the Hercules Graphics Adapter, the Color Graphics Adapter (CGA) and the Plantronics Plus graphcis card. The functionality was later duplicated on EGA and VGA hardware for backward compatibility.

Source: WikiPedia

The Z80 quickly became popular in the personal computer market, with many early personal computers, such as the TRS-80 and Sinclair ZX80, using the Z80 as their central processing unit (CPU). It was also widely used in home computers, such as the MSX range, SORD, and the Amstrad CPC, as well as in many arcade games. Additionally, it was also used in other applications such as industrial control systems, and embedded systems. The Z80 was widely used until the mid-1980s, when it was gradually replaced by newer microprocessors such as the Intel 80286 and the Motorola 68000.

The Z80 microprocessor was developed by Zilog, a company founded by Federico Faggin in 1974. The Z80 was released in July 1976, as a successor to the Intel 8080. It was designed to be fully compatible with the 8080, but also included new features such as an improved instruction set, more powerful interrupts, and a more sophisticated memory management system.

Originally the Z80 was intended for use in embedded systems, just as the 8080 CPU. But the combination of compatibility, superior performance to other CPUs of the era, and the affordability led to a widespread use in arcade video game systems, and later in home computers such as the Osborne 1, TRS-80, ColecoVision, ZX Spectrum, MSX, Sega's Master System and many more. The Z-80 ran the original Pac-Man arcade cabinet. The Z-80 was used even in the Game Gear (1990s), and the TI-81 and succeeding graphic calculators.

The Z-80 remained in production until June of 2024, 48 years after its original release. Zilog replaced the processor with its successor the eZ80, an 8-bit microprocessor that features expanded memory addressing up to 16 megabytes, and running up to 50MHz, comparable to a Z80 clocked at 150MHz.