Sinclair QL
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(pictures copyright by M.A.Grundke)
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serial number:
D13-053077'D13' indicates the build standard (B/S) and board issue. Machines from B/S D14 on made use of an ISSUE 6 board, so D13 indicates the usage of an ISSUE 5 board |
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type (bottom of the machine):
SINCLAIR QL Professional Computer
no user serviceable parts inside.
use only approved AC adaptor.
Designed in Cambridge, England
by SINCLAIR Research Ltd.made in UK
© 1983 SINCLAIR Research Ltd.
Patent Applications, Design Applications |
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Sinclair QL ISSUE 5 board overview:
beginning from the left, you can see the machine's internal expansion port, with room for the various expansion devices. Right from there, below the cartridge connector, are the machine's CPU (IC18), the ULA (IC22), two 74LS257 (IC19, IC20) and a 74LS245 (IC21). Interesting in this machine is, that a PAL14L4 was soldered onto IC21 - necessary because of the internal RAM expansion. Further right, the RAM bank (consisting of 16 pcs. 256Kx1 in this machine, IC1-IC16), and the two ROMs (256Kx1 & 128Kx1 at IC33, IC34) above. Right, again, a 74LS03 (IC27),
MC1488 (IC25) and the ZX8302 (IC23). Still right, the MC1489, and the keyboard connectors below. Still moving right, there's the 8049 IPC and the two Microdrives. Behind the drives, clearly dominating the machine's right, is the power voltage regulator with its large heatsink. Left from there, below the RF-modulator, the MC1377 (IC24). Not visible because lying under the heatsink, finally, is the machine's connector for external Microdrives. The heatsink, by the way, is the QL's weak spot - it's getting very hot upon operation, and makes the surrounding plastic brittle - a typical sign of 'QL-ageing'... |
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board silkscreening, part 1:
sinclair QL
© 1984
ISS 5 |
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board silkscreening, part 2 (lower boardside):
sinclair
QL 1984 ISS.5 |
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| The rare and interesting Motorola MC68008 CPU. It looks like a standard DIP-package MC68000 or MC68010, but in comparison to them, it has an 8 bit data- and 20 bit address-bus (MC68000/ 68010/ 68012: 16 bit data-, 24 bit address-bus). Interesting is that two versions of the MC68008 did exist: a 48 pin DIP package version (used here, 20 bit address-range), and a 52 pin PLCC package version (with 22 bit address-range). Below, however, the the QL's internal, 68 pin expansion bus,
for which many expansions were available: RAM expansions, Shugart-, SCSI- and AT-bus adaptors or even CPU boards. The Miracle Systems Gold Card, for example, contained a 16 MHz MC68000, floppy controller and 2 MByte RAM. The use of another CPU is possible because one of the expansion port's signals disables the onboard MC68008 (similar to the Amiga 2000's MMU-slot) |
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| The Intel 8049H111 IPC ('Intelligent Peripheral Controller') is a microcontroller and clocked at 11 MHz (here a NEC-manufactured version). It contains 2048 bytes ROM and 128 bytes SRAM, and is responsible for RS232 communication (by controlling MC1488/ MC1498), keyboard scanning, speaker- and joystick control. Since the original i8049 occasionally had problems with serial communications (only 9600 baud possible), sound playback and keyboard scanning ('keybounce'), replacements were available - generally in the form of an Intel 8749
(which is the i8049's EPROM-version and fully compatible) with modified firmware. As to my current knowledge, no QL came with an i8749 by default, since for many users, the known i8049 issues were simply irrelevant. One of these i8749 upgrades was called 'Hermes', and solved almost all problems mentioned above (e.g. baud rates up to 19200 baud possible and no more 'keybounce') |
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| ZX8301, a Sinclair-developed custom chip (here from an unknown manufacturer). It is responsible for creating the RGB signals for TV- and monitor-output, address decoding, refreshing DRAM and master clock generation. When the ZX8301 does video refresh and thus accesses memory, the CPU is halted in order to assure correct video output |
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| The machine's RAM bank, 16 pcs. Texas Instruments TMS4256-12NL (256Kx1), for a total of 512 KBytes internal RAM. From the fab, the QL was fitted with 16 pcs. 64Kx1 RAMs (128 KBytes). This particular machine has been modified and upgraded with the pin-compatible 256Kx1 RAMs. However, the higher density RAMs need an additional multiplexer for address selection, as well as some wiring, since the QL can only manage four 64K blocks in its original state: internal ROM, I/O area, lower 64K & upper 64K. Positive side-effect of the upgrade: all RAMs have been socketed (normally, they're soldered directly to the board) |
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| The QL ROMs, in the 'JM' version (aka v1.03), consisting of a 256Kx1 (32K) and a 128Kx1 (16K) ROM. This version arrived in late 1984 and was, together with the earlier 'AH'-version (v1.02), almost free of bugs. Additionally, an external cartridge with additional chips ('dongle') wasn't required anymore. It was also the first version to come in two chips (earlier revisions either came in one chip plus external 'dongle', or three chips, where the third was mounted 'pickaback' on one of the others) |
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| The Motorola MC1377P RGB-to-PAL/NTSC encoder creates a composite signal from the machine's RGB- and Sync-signals (outputted by the ZX8301) for the RF-modulator. Since it is PAL and NTSC-compatible, the QL could also be sold to the US, with only small modifications. The 'P'-suffix, by the way, indicates plastic DIP20 package |
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| The machine's integrated loudspeaker, which is located below the Microdrives, and is controlled by the 8049H. However, changing its volume is not possible! |
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| This is one of the two Microdrive controller boards, each with a Ferranti 2G007E ULA (IC29 & IC30). The ULA controls the drive motor, and is responsible for amplification and digital conversion of the signals outputted by the drive's head. The signals are then fed into the ZX8302. When data is to be written, the process is done in the opposite way |
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| This is one of the QL's built-in microdrives. You can see the drive's head that reads the tape just like a standard cassette-player. On its right side is a microswitch (which was, by the way, very common in the digital joysticks these days), that's exerting pressure on a small metal spring. It's required for inserting and ejecting the microdrive cartridges.
The use of these common, standard parts made microdrive-production quite cheap, and is a good example for Sir Sinclair's ability to create clever solutions from scratch (microdrives are a Sinclair-invention!) |
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| The same drive, but now with a microdrive media inserted (QL Archive, part of the software package that came with the machine) |
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| ZX8302, also referred to as 'peripheral control chip'. It controls all peripheral signals, like Microdrive, RS232, QLAN and interrupts, and provides real-time clock function. Additionally, it is connected to the 8049 to access keyboard-, joystick- and speaker-signals as well. The Microdrive control functions are, by the way, identical to those of the Sinclair Interface 1. As you can see, there are two resistors soldered to pins 19 and 21 of the ZX8302 (and to VM12 on the board). This was an official 'Sinclair mandatory modification' (a.k.a. patchwork), which
was recommended to resolve certain issues with the board (which issues, exactly, is unknown) |
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| Motorola MC1488 (quad-line serial driver) and MC1489 (quad-line serial receiver) are controlled by the 8049 and responsible for low-level RS232 communication (i.e. physical connection to RS232 devices, assuring that the proper signal levels are met etc.). These were cheap standard-components and implemented in most computer designs these days |
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| Looking at the machine's back, you can see the non-standard, 6 pin 'QL connectors'. They look like registered jacks (RJ), but with the holding clip left from the pins (instead of above them) - from what I've heard, these are english telephone jacks (?). The SER ports are RS232 compliant, and the CTL ports were intended for special QL joysticks. According to Elmar Duensser, some european machines came with SUB-D connectors instead of the telephone jacks (although I've never seen one yet) |
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| Here a closeup on the interesting QLAN ports (labeled 'NET'), which could be used to connect the machine to other QLs at 100 KBit/s, after all (though I don't know if there have been any applications for that). Right from there, PSU connector and the round DIN video port. As you can see, almost all QL connectors are non-standard... Even more interesting is that the video port contains both digital RGB and composite video signals, making the QL quite flexible |