Why was the QL never successful?

[Peter]

I don't see a "Centronics" parallel printer port as being hard to design or that expensive to include compared to a serial port. One 74LS series latch chip, a CS output from one of the ULA chips (to control the 74LS series latch chip) and using two I/O pins of the 8049 IPC (strobe and busy lines), plus of course the connector and your done

I didn't say hard to design. However, PAR needed signiicantly more board space and PCB traces than SER, while the board had only two layers and was already so overpopulated, that signal quality suffered. Additionally PAR required ESD/EMI termination components, direct connetion to ULA/74LS would have resulted in a lot of dead QLs.

The Acorn BBC B computer can do it. So I do not see why the Sinclair engineers could not do it.

In simple designs, there is a relationship between CPU clock and pixel clock. Timings of the 68008 were already tight, using the chip technology of the ULA, so it was not trivial to push CPU clock. BBC had only a 6502, with easier slower timings.

[adev]

The Acorn BBC B computer can do it. So I do not see why the Sinclair engineers could not do it. And suitable monitors were available.

True, but it's properly headache-inducing on the standard Microvitec CUB monitor.

[polka]

1024MAK wrote:
A standard video signal so that existing designs of VDU ( monitors) could be used rather than people having to buy special QL compatible VDUs.

I don't see an issue here ; in 1985, I bought an "Oceanic" branded VDU with a SCART input for 1V/75ohms standard RGB and Csync signals (basically like a normal TV set without a tuner - suited for VCRs with a tuner). And made for it a cable following this scheme :

To be noted : the first cable I made had not the 5V wiring - it was not needed - but soon I added a double inverter switch to exchange G and B signals, in order to get a four color image with black-red blue-white instead of black-red-green-white for high-res. stereo pictures viewing through red-blue goggles.

When I wanted to use other "normal" TV sets through their SCART input, I had to make a second cable without the switch (lazy guy) but with the 5V wiring added ; indeed, I had to modify one of my QLs to add a one wire plug beside the video output. This cable never failed to feed any TV set with a SCART input (even my modern large LCD screens) and always yielded very good resolution both in 8 or 4 color modes.

Bye Paul