[GTALUG] old computer / new computer

[D. Hugh Redelmeier]

When I started playing with computers (1967) mainframes were the thing (we 
called them computers).

The University of Waterloo got an IBM SYSTEM/360-75, the biggest computer 
in Canada, in 1967 or 1968.  It filled a lot of the "Big Red Room", a
jewel case the size of gymnasium.

Eventually, it had 1MiB of core memory and 2MiB of LCS (slow core
memory).  It ran most of the computing work for the whole campus,
including student programs.

The successor to this hardware is IBM's System Z.  The latest announced 
processor chip has 512MiB of cache per socket.  I have no idea how many 
sockets a large system would have.

The /360 architecture only allowed for 24 bits of address -- 16M.  The 
/370 eventually allowed for 31 bits of address.  I don't know what Z's 
limits are.  Anyway, the whole contents of the 360-75 core would occupy 
1/512 of the cache of one socket of the Z.

The -75 didn't even have a cache.  The -85, introduced a couple of years 
later, did.  When an Ottawa company (SDL?) got one, that became the 
largest computer in Canada.

The fastest instructions on the 360-75 (for example, adding two registers) 
took .39 microseconds.

On my main computer in those days, the IBM 1710 Model 2, the fastest 
instruction took 70ns, plus 10ns for each pair of digits processed.  The
-75 was a LOT faster.

Now ordinary PCs are 2GHz or more and execute better than 1 instruction 
per cycle.  Perhaps 1000 times faster than the 360-75.

Bulk RAM is perhaps only 10 times faster.  But cache has a large effect.

Disk latencies might not be a lot better: 2,400 RPM vs 10,000 RPM but seek 
times, capacity, and bandwidth are.  Not to mention SSDs.

I cannot even estimate power requirements.  And you have to add power for 
cooling.

The price is perhaps 10,000 times lower.

You can see why I'm not really impressed with x86 improvements since 
Haswell.