🚀 go-pugleaf

newwave@desire.wright.edu writes:

>    Is it true that the VAX 8650 outperforms the VAX 8200 6 times.
> 
>    Why is it that a VAX 8200 outperforms the VAX 8650 10 times on a UNIBUS
>   write cycle?

Because it isn't UNIBUS.  It's VAXBI.  I've seen 8200s go to 100% cpu
utilization for long periods while doing backups -- the bus simply isn't
the bottleneck..... (this was in older versions of VMS BACKUP, before
I/O efficiency was improved....).  I've never seen UNIBUS connected
peripherals do that to a machine.  Not even 11/750s.

>
>    What can be done to improve the 8650 performance.

You could attach a CI and an HSC.  It'll cost $$$ though.  If the 86xx
series includes a MASSBUS (does it? never met one), get MASSBUS devices
... until fairly recently (ie latest CI controllers), MASSBUS connected
RM05s were easily the fastest things on spindles if driven properly.
Seek times weren't as good as RA disks, but sheer throughput........
Keep the disk defragmented, use a large cluster size and watch it fly.
(I only ever used then on PDP-11/70s -- 24k block I/O to RM05s meant
*incredible* speed if you knew what you were doing.)

Bear in mind that RM05s are an old drive; you might be able to pick them
up very cheap second hand.  They're big, power hungry removable pack jobs.
Be prepared to have to move them back against their controller cabinet
periodically -- they walk.......

Don Stokes, ZL2TNM  /  /                            Home: don@zl2tnm.gp.govt.nz
Systems Programmer /GP/ Government Printing Office  Work:        don@gp.govt.nz
__________________/  /__Wellington, New Zealand_____or:_PSI%(5301)47000028::DON