Why did Sinclair hate National Semiconductor?

[Dave]

From the QL Service Manual, it seems Sinclair Research had no love for National Semiconductor.

Is there a backstory to this?

[XorA]

Ah crap I have seen this somewhere before (not for QL) but I can't remember where!

[Pr0f]

I wonder if it was a loading issue, or maybe slew rate ?

Without comparing the data sheets for NAT semi and maybe TI or whoever else also made the LS series of logic, it's hard to say.

[Zarchos]

You'll have to check the various interviews on YT, but I remember Steve Furber or Hermann Hauser (Acorn) explaining
that the Beeb did (or did not) work (only, or no at all) with some NS chips.
And they never understood why. (For the exact same specs compared to equivalent parts from other founders).

[1024MAK]

They DID NOT hate National Semiconductor.

Every manufacturer of so called standard 74 series logic uses their own internal logic design to fulfill the overall logic function. This means that logically, a 74 series part from any manufacturer should work. However, timing wise, they may not work the same. And any undocumented features or functions may also not be the same (for example, undefined logic states).

Sinclair found that some 74 chips from National Semiconductor did not work the way they wanted them to. Hence the warnings in both the ZX Spectrum and QL service manuals.

But other manufacturers also some chips that were not recommended in some applications.

Mark

[Silvester]

My old Elektor data book remarks the Hitachi 245 has Schmitt inputs, which make them suitable for noisy signals.