The first book to deal with the insides of the Spectrum, Spectrum Hardware Manual by Adrian Dickens, must be a welcome addition to any constructor or student of computers, writes Stephen Adams.
It provides an insight on how the computer works and then describes the Spectrum in detail, including complete circuit diagrams of everything, except the ULA.
The user has to be satisfied with a pin-by-pin description of that device. The author describes its workings in simple detail and does not indulge in technical jargon. The circuit principles are explained but not component by component, except where the author is sure of his ground, i.e., the power supply, CPU and RAM chips.
The video section is a little misleading as it refers to B-Y as BLUE-YELLOW, where in real life the Y stands for luminance - the whiteness of the picture. It gives the adjustments necessary to deal with some problems associated with the video.
One-third of the book is circuit diagrams and descriptions of circuits the user can add to the back of the Spectrum. The author seems a little nervous about suggesting that the user make improvements inside the Spectrum. A port made from a PIO, add-on joysticks, plus an exterior keyboard are also described. One suggestion for model one users only is to allow for 127 extra ports by improving on the decoding for the I/O map.
The differences between the models one and two are pointed-out frequently, with photographs to show the components on the circuit board. A "dead cockroach" IC and the transistor across the model two Z-80A CPU are described, along with why they were necessary.