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Sothius' Home-Museum- Sinclair-Sinclair ZX Spectrum 48K-additional pictures

Sinclair ZX Spectrum 48K
Additional pictures. Note that loading the page could take a while...
(pictures copyright by M.A.Grundke)

ZX Spectrum 48K serial number (23 KBytes)
serial number:
005-511618


ZX Spectrum 48K type plate (34 KBytes)
type (bottom of the machine):
sinclair
ZX SPECTRUM PERSONAL COMPUTER
USE ONLY APPROVED AC ADAPTOR
PATENT PENDING
MADE IN UK


ZX Spectrum 48K board overview (92 KBytes)
ZX Spectrum 48K ISSUE 6A board overview:
in the top left corner the machine's RF modulator with MIC- and EAR-ports to its right. Below these, the ULA (IC1) and the first 16 KByte RAM bank below it (8 pcs. 16Kx1 DRAMs at IC6-IC13). Right from there the expansion RAM bank (8 pcs. 64Kx1 DRAMs, used as 32Kx1 in the Spectrum, locations IC15-IC22) and the loudspeaker (further right). Above the expansion RAM a PFC1306P (IC27), the Zilog Z80A CPU (IC2) and the Spectrum's ROM (IC5, from left to right). Note that all these are partly covered by the voltage regulator's heat spreader (the regulator is on the righmost side of the spreader, below the PSU connector and right from the ROM). Also covered by the spreader here is the machine's expansion port


ZX Spectrum 48K board silkscreening part 1 (33 KBytes)
board silkscreening, part 1 (board's upper side):
sinclair ZX SPECTRUM © 1984 ISSUE 6A


ZX Spectrum 48K board silkscreening part 2 (42 KBytes)
board silkscreening, part 2 (board's lower side):
sinclair
ZX SPECTRUM
©1984 ISSUE 6A


ZX Spectrum 48K board silkscreening part 3 (30 KBytes)
board silkscreening, part 3 (again board's lower side):
I PCIB PCP


ZX Spectrum 48K CPU (56 KBytes)
One of the most popular CPUs ever was the Zilog Z80 (here the 'A'-version). It was a descendant of the Intel 8080 and to a certain extent compatible with its commands


ZX Spectrum 48K PFC1306P (57 KBytes)
This additional ULA (here a PCF1306P, sometimes a Mullard ZX8401) is found on all ISSUE 5 and higher boards. It replaces six chips used as RAM address decoders and multiplexers used in the older machines (IC3/4, IC23/IC24 and IC25/IC26), reducing production cost. See below for the main ULA


ZX Spectrum 48K original RAM (71 KBytes)
The Spectrum's first RAM bank (sometimes called 'original RAM') consists of 8 pcs. 4116-type (16Kx1) DRAMs (here STC 8451), which are soldered directly to the board. In the Spectrum 16K, this is the only system RAM, while the Spectrum 48K comes also with the expansion RAM bank equipped (see below)


ZX Spectrum 48K expansion RAM (54 KBytes)
The machine's second RAM bank, often called 'expansion bank' since these sockets are not fitted in the Spectrum 16K (but because of the sockets, it can easily be expanded to the full 48K). However, in the Spectrum 48K (this one), the expansion RAM bank is completely filled. Interesting is that although the RAM is addressed as 32Kx1 in the Spectrum-design, they used 64Kx1 DRAMs (8 pcs. Samsung KM4164B) here (and in many other machines I've heard of) - these were a charge of faulty RAMs with one half of their capacity being not accessible. Perhaps Sinclair had bought a great lot of these at a good price? However, there probably were machines with 32Kx1 DRAMs, although I've never seen one


ZX Spectrum 48K ROM (22 KBytes)
The Sinclair Spectrum's 16K BASIC ROM, containing the operating system and BASIC interpreter. In comparison to its ancestors' ZX81 BASIC 8K, there were many improvements like an ASCII character set instead of a non-standard one, new commands for the machine's advanced capabilities and other improvements in detail (e.g. new options for existing commands). Additionally, ZX Spectrum BASIC is to a great extent compatible with ZX81 BASIC


ZX Spectrum 48K ULA (60 KBytes)
The ULA Logic Gate Array, which is in this case (ISSUE 6A-board) a Ferranti ULA 6C001E-7, is responsible for I/O-functions such as the tape-interface. It is comparable to the ZX81's SCL ('Sinclair Computer Logic'), except for the fact that it is also used for generating graphics output - in ZX80/ ZX81, this is done entirely by the CPU. However, beginning with the ISSUE 5 boards, a second ULA was added (see above), and the first one was called 'main ULA' from then on


ZX Spectrum 48K speaker (38 KBytes)
The ZX Spectrum's onboard loudspeaker is a cheap but also a poor solution for outputting sound


ZX Spectrum 48K expansion connector (26 KBytes)
The Spectrum's 54 pin expansion port, which contains all Z80A signals. It was used for connecting the ZX printer, communication devices (e.g. RS232 interface) and drives (ZX Microdrive and diskdrives, coming with their own controller logic or interface)



Also see the ZX81 page for a Sinclair Computer Logic (SCL) picture
(which was the ULA's ancestor)


Sothius' Home-Museum- Sinclair-Sinclair ZX Spectrum 48K-additional pictures