10 Jun
2010
10 Jun
'10
5:05 p.m.
Ben <bfranchuk at jetnet.ab.ca> wrote:
Looking back with the emulators, of vintage hardware
it is the fact that expensive things like mass-storage
could be shared among several people. I have just been
installing some PDP 8 software on a IDE drive and even
with the small size of PDP 8 disks ( 2048k max ) you
sure can see how small programs and data was back then.
With a PDP 8 multi-tasking the programs I expect where
dog slow, but they could run with larger memory and
disks a larger machine could justify.
In all fairness, there is no such limitation on the size of disks on
PDP-8s. OS/8 have a limitation on disks being no more than 4096
*blocks*, but that's a limitation in that OS, which is based on the fact
that just one word is used to specify the block number for device drivers.
Larger disks (which weren't that unusual) had to be presented as several
logical disks to the OS, in order for them to be fully used.
So an RL02 (as an example) looked like five disks to OS/8. RL0A, RL0B,
RL0C, RL0D and RL0E. All about 2M each.
As for multi-tasking - no, that was/is not dog slow. Most of the time it
was perfectly fine even for several interactive users in parallel.
Johnny
11 Jun
11 Jun
1:45 a.m.
Johnny Billquist wrote:
As for multi-tasking - no, that was/is not dog slow.
Most of the time
it was perfectly fine even for several interactive users in parallel.
And why was the PDP-8 not dog slow doing simple things like editing text
files? Because people wrote software *carefully* back then. They
didn't code as if the CPU were infinitely fast; they didn't use any more
instructions than were absolutely necessary.
Sure, the processor executed well under a million instructions per
second, rather than billions of instructions per second of modern
processors. And that's only instructions that operate on 12-bit data,
rather than 32-bit or 64-bit today. But writing a character to the
system console via a handler in the operating system only required
executing a few dozen instructions on a PDP-8, versus executing
thousands of instructions today. I just checked on my Linux x86_64
system, and on average writing a character to the console requires
executing over six thousand instructions.
Eric
--
And in those days many a clever programmer derived an immense
intellectual satisfaction from the cunning tricks by means of which he
contrived to squeeze the impossible into the constraints of his equipment.
--- Edsger W. Dijkstra, "The Humble Programmer", 1972 ACM Turing
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