On Tue, 13 Dec 2022, Rudi Blom wrote:

> I vaguely remember having read here about 'clever code' which took into
> account the time a magnetic drum needed to rotate in order to optimise
> access.

Sounds like you're referring to SOAP (Symbolic Optimal Assembly Program) 
on the IBM 650; the programmer wrote the code "straight down" and SOAP 
reordered it for rotational latency.

> Similarly I can imagine that with resource restraints you sometimes need to
> be clever in order to get your program to fit. Of course, any such
> cleverness needs extra documentation.

Try writing a bootstrap program in 512 bytes :-)  Self-modifying code was
the order of the day...

> I only ever programmed in user space but even then without lots of comment
> in my code I may already start wondering what I did after only a few months
> past.

You could be clever in kernel space too, such as taking advantage of
the DATIP/DATO cycles on DEC's Unibus when updating a memory word i.e. 
read/modify/write.

-- Dave