Date: Sat, 9 Oct 1999 14:02:25 +0200 (MET DST) From: Gerard Roudier <groudier@club-internet.fr> To: "Matthew N. Dodd" <winter@jurai.net> Cc: Randell Jesup <rjesup@wgate.com>, scsi@FreeBSD.ORG Subject: Re: Driver for GDT6517RD RAID controller Message-ID: <Pine.LNX.3.95.991009131106.818A-100000@localhost> In-Reply-To: <Pine.BSF.4.10.9910082023440.480-100000@sasami.jurai.net>
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On Fri, 8 Oct 1999, Matthew N. Dodd wrote:
> On 8 Oct 1999, Randell Jesup wrote:
> > Nice results. I haven't played with 53c8xx chips, but I wrote some
> > very fast drivers for the 53c7xx chips a long time ago ('93) for the
> > Amiga.
>=20
> I'd be interested in hearing your observation of the differences between
> the 53c7xx and the 53c8xx chips as I'd really like to see the existing NC=
R
> driver support them.
One year ago, I asked SYMBIOS about their opinion of having good support
under Linux for 53c710 and later 7xx chips (basically the 720). They were
absolutely not interested in this and even discouraged me to provide such
support. The FreeBSD case should not be that different in this regard. In
fact, the 7xx chips are only used nowadays as generic SCSI core for some
intelligent controllers.
> I suspect that all but the very early 53c700 and 710 chips would require
> minimal changes.
The 53c700 must be considered as having never existed. ;)
About the 710 and later 7xx chips, speaking of a driver for this family
does not make sense, since the system BUS stuff allows and requires
proprietary implementations from the system hardware. Since it seems that
machines that use on-board 7xx controllers are old, the needed
documentation may just be no longer available.
A driver that will separate system BUS code and SCSI core code may allow
to support some set of 53c7xx based controllers. The 53c7xx support looks
like that under Linux, for example.
Basically, a SIM that supports 53c810 rev 1 can support 53c710 and later
53c7xx chips with minimal changes, provided that the BUS stuff be added or
changed. The stock ncr driver supports the 53c810 rev 1, so starting from
this code should be just fine for some 710 support.=20
No chance at all with the sym_hipd driver I am currently developping,
since the aim of this driver is to take advantages of recent chips and
PCI bus.
Now, my 0.02 euro opinion about this topic:
I am always been amazed by people who wants latest softwares to support
old hardwares. If such compatibilty constraints had been always applied,
may-be the fastest hardware nowadays would be a Z80 at 5 GigaHz and
graphic would be some incredibly fast 16 colors VGA. ;-) Note that the
poorness of latest IA32 arch we have to deal with may well be due to some
backward compatibility + $$ issues. IMO, the 53c7xx parts are now material
for history books and IT museums, and an O/S that does not provide support
yet for these chips should not consider adding such a support, unless some
driver magically be provided by some volonteer and be actually
_maintained_.=20
G=E9rard.
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