2 hardrives of different interfaces allowed to coexist?

[Doug Pintar]

In article <1990Aug22.061223.15564 at fiver> palowoda at fiver (Bob Palowoda) writes:
>
> Ahh, somebody mentioned the magic word "secondary" controller. Has anyone
>ever tested this setup. Say with the second disk controller on interupt 15?
>ISC? ESIX? or SCO UNIX?

Yes, I have.  The ISC HPDD will support a secondary AT controller, given
	1) secondary I/O addresses,
	2) if it has a floppy controller, it must be disabled, and
	3) [the biggie] a secondary interrupt (usually 15).
The reason 2 is of concern is that very few controllers offer it.  The only
ones I've seen to date are the Adaptec 232x ESDI and 237x RLL.  I have used
a WD-1007 (Compaq flavor) with a 300 MB ESDI drive as primary and an Adaptec
2320 with some other flavor ESDI drive on it.  Works fine, BUT... when you
get both drives going at the same time (the AT controller is PIO, remember)
the CPU starts to get swamped handling interrupts and moving data to/from the
controllers.  I found my max (raw, large-buffers) transfer rate on either
drive alone was around 850 KB/sec and that both together topped out at an
aggregate of about 1.3 MB/sec.  This is on a 20 MHz Compaq, faster CPU would
help with the interrupt overhead, but probably not with the 16-bit string
moves to/from the controllers.

The HPDD will also support a SCSI adapter as a secondary controller (the
machine I'm writing this on has 1.4 GB of Maxtor 8380s hanging off an Adaptec
1542B in addition to the ESDI primary).  For pure performance, having the
first-party DMA of the 1542 off-loads BUNCHES of overhead from the CPU.  I
just wish I could run mine faster than 5.7 MB/sec burst rate, sniff sniff...
DLP