>> How about drum memory? Or the various delay lines?
> 
> Don't know, was before my time.

OK. So care is newer than either of those.

> I don't know very much about the actual electronics.

OK.

> Most really large files were on tape, you just read the data serially.
> For highly accessed files, or files that needed random access were kept on disk.

So the concept of a filesystem storing named files already existed at 
this time?

> The file system for IBM mainframes are record oriented, not stream.
> Files are created with a defined record format and record length.

Interesting. So the system actually "knows" where each field of a record 
is then?

>> What sort of access speeds do you get for reading or writing punched
>> card or tape?
> 
> As I recall about 60 characters per second.  The tape was paper, was 8 holes
> wide, and easily broken or scrunched.

Mmm, that's fairly fast for an optical system.

> On some of the older machines I worked with:
>   360/50 128KB
>   370/158 1MB
>   370/168 3MB
>   3033U 4MB
>   3081Q 8MB
> On the latest machine:
>   z/9 BC S03 - 16GB

I should probably go plot that on a graph against date or something... ;-)

>> Nice consistent naming scheme. Heh. :-/
> 
> You can always depend on IBM to be consistent.

Consistently inconsisten. ;-)

Still, some things never change:

   nVidia GeForce 8xxx
   nVidia GeForce 9xxx
   nVidia GeForce 2xx   <- WTH?

>> Now if I could figure out what a typical MIPS rating for a normal PC
>> today is, I'd have something dissimilar to compare it to. :-}
> 
> It is rather difficult to compare since they have such different architectures.

Yes, that's what I meant by "dissimilar comparison". It all rather 
depends on how many registers you have, how wide the various data busses 
are, what operations you can perform in hardware (e.g., is 
multiplication a hardware or software operation?), and so forth.

> I doubt that the internal processor speed is that much different than current
> PCs, but the i/o bandwidth is much higher in the mainframe.

Really? I didn't think anybody had mainframes any more... just big 
server farms.

> For example our two machines, which are on the small side for mainframes, are
> connected to a disk storage unit containing 15TB of data.  There are 4 high
> speed fiber optic channels from each processor to this unit. We can easily
> sustain i/o rates of over 10000 i/o operations per second, with peaks in the
> 20000 to 40000 range.

Sounds expensive.

> It is very rare for any single job to saturate the cpu.
> By running many jobs concurrently we make full use of the machine.

The *original* purpose of multitasking operating systems. ;-)

> If I could
> port POVRAY to our mainframe, I'm sure it would be slower than most current PCs.
> But cpu intensive work is not what the mainframe does best.

Out of curiosity, what *do* you use it for?

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