> And almost all high-end Ethernet and SCSI cards have functionality
> equivalent to a channel.
Which is why my AMD 586x133 eats a lot of 100 Mhz Pentiums
for lunch. The Adaptec 2742 is quite a nice VLB controller.
>
> The 486DX2/66 systems Mike C. was comparing to obviously didn't have the PCI
> bus-mastering ATA disk interface. But for server applications those
> systems were typically configured with an Adaptec 1542 SCSI controller, which
> served as a very intelligent channel processor.
Yup... and the 1542 was pretty minimal compared with the CAM supporting
SCSI stuff out there now with tagged queueing.
>
> No, there was no way that the system would have had adequate performance if
> it had to support that many users doing serious software development.
>
> But then, neither could the VAX. The 8650 which I used in the mid 80s would
> serve 50 users easily as long as only a few people were doing memory and CPU
> intensive things. But if more than three or four people tried to do a compile
> at once, performance went to hell. Which would have been OK if only the
> compute-bound jobs suffered. But the scheduler couldn't cope will enough, so
> even the "light" jobs became unresponsive. This is because everything that
> was learned in the 1960s and 1970s about building good timesharing systems was
> subsequently forgotten in the early 1980s.
>
What OS? BSD? Ultrix? VAX/VMS?
Actually, the scheduler on VAX/VMS was pretty good if tuned well.
I've had 50 developers on an 8650 without problems. The trick was
putting the compiles in via batch at a priority behind the folks editing
code...
(Of course me running 50 copies of the CPU and floating point diags at
priority 10 on an 11/780 left the EDT users thinking the machine had gone south.
But it did pull the intermittant errors and help me fix one machine.)
Bill
---
bpechter_at_shell.monmouth.com|pechter_at_pechter.dyndns.org
Three things never anger: First, the one who runs your DEC,
The one who does Field Service and the one who signs your check.
Received on Mon Oct 25 1999 - 08:32:23 BST