In deep sinclair zx spectrum mod#
In deep sinclair zx spectrum mods#
In deep sinclair zx spectrum plus#
In deep sinclair zx spectrum series#

This is a comparatively rare revision, and seems to be the first attempt by Sinclair to use FerrantiвЂ™s new 6C process to reduce ULA power consumption. It is unclear at this time what the differences between the original 5C112E and the -2 and -3 variants are. If the transistor isnвЂ™t present then the machine will work properly except for the absence of the floating bus effect (see this article for a more detailed explanation).

In deep sinclair zx spectrum mod#

The mod was performed with a single diode and resistor on early Issue 2 machines.Дue to lack of available pins to properly fix this issue in subsequent ULA revisions, this transistor became part of the PCB layout (TR6) in Issue 3 and later PCBвЂ™s.

This resulted in the implementation of the вЂspiderвЂ™ mod, a ZTX313 transistor soldered over the CPU (or next to the upper RAM ICвЂ™s in some models). It fixes the initial I/O contention issue, but unfortunately it was found that the resulting I/O contention was overly aggresive, contending ports that did not need to be. This was the second revision of the ULA and is found in Issue 2 Spectrums. It suffered from a buggy I/O contention model which made I/O reads, particularly keyboard reads from machine code, unreliable, hence the addition of the вЂcockroachвЂ™ mod (basically a 74LS00 chip hand soldered on top of the PCB with flying lead connections, later contained on its own mini daughterboard). This was the original ULA type, and is to be found in Issue 1 (and a small number of Issue 2) Spectrums. The 16/48K Spectrum can be found with a number of different ULA types:

In deep sinclair zx spectrum plus#

This was a technology pioneered by Ferranti, of which Sinclair was one of the first adopters (incorporating all of the discrete logic of the ZX80, plus a NMI generation circuit into the initial ZX81 2C158E ULA).

In deep sinclair zx spectrum series#

Items are new / unused unless stated.The heart of the ZX Spectrum series of computers is a custom chip called the ULA (Uncommitted Logic Array). I have sourced as many replacement parts as I can fine and listed them here. The quintessentially British home computer is now 30+ years old and most will have been through some rough treatment (and then left in the loft for decades!).

In deep sinclair zx spectrum mods#

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