Sorry for crossposting, but I didn't get any response to this on the
user list.
---------- Forwarded message ----------
Date: Tue, 21 Mar 2000 02:12:47 +0100 (MET)
From: Derek Homeier <redacted>
To: linuxppc-user@lists.linuxppc.org
Subject: Synchronous SCSI at 10MB/s on Lombard?
One more question...
Has anyone tried to set the rate for synchronous SCSI tranfer for the MESH
controller in the G3 series Powerbooks to 10? The kernel docs claim it does
10 MB/sec on machines where the bus is internal only:
CONFIG_SCSI_MESH_SYNC_RATE: x
x x
x On Power Macintoshes (and clones) where the MESH SCSI bus adaptor x
x drives a bus which is entirely internal to the machine (such as the x
x 7500, 7600, 8500, etc.), the MESH is capable of synchronous x
x operation at up to 10 MB/s. On machines where the SCSI bus x
x controlled by the MESH can have external devices connected, it is x
x usually rated at 5 MB/s. 5 is a safe value here unless you know the x
x MESH SCSI bus is internal only; in that case you can say 10. Say 0 x
x to disable synchronous operation. x
but for an uneducated test I have set it to 10, and this seems to work so
far on my Lombard. The throughput as reported by hdparm has effectively
doubled (from 3.3 to 6.6 MB/s), so does anyone know whether this is
safe or there are any dangers implied when setting the transfer rate that
high (if it only you could call this high!) on the external bus?
Thanks for any advice,
Derek
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
From: Joseph Garcia <hidden> Date: 2000-03-23 18:08:31
Derek Homeier wrote:
Has anyone tried to set the rate for synchronous SCSI tranfer for the MESH
controller in the G3 series Powerbooks to 10? The kernel docs claim it does
10 MB/sec on machines where the bus is internal only:
I have tried it on my PDQ/300. My SyQuest worked fine, but according to /proc,
it was still running at 5. however, my yamaha cdrw did not work. set 5, it
reports its sync speed is 4.2. when MESH is told to max at 10, my RW is still
recognized, reports 8.4, but does not respond to mounting, reading, nor
writing. It could be that the 6.6 you have achieved is still doable, but my 8.4
is not. so setting MESH to 7 or 8 may be a safer fast speed. havent tried it
though.
--
Joseph P. Garcia jpgarcia@execpc.com jpgarcia@lidar.ssec.wisc.edu
CS Undergraduate Student Employee - Systems Programmer
University of Wisconsin - Madison UW Lidar Group
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
Has anyone tried to set the rate for synchronous SCSI tranfer for the MESH
controller in the G3 series Powerbooks to 10? The kernel docs claim it does
10 MB/sec on machines where the bus is internal only:
I have tried it on my PDQ/300. My SyQuest worked fine, but according to /proc,
it was still running at 5. however, my yamaha cdrw did not work. set 5, it
reports its sync speed is 4.2. when MESH is told to max at 10, my RW is still
recognized, reports 8.4, but does not respond to mounting, reading, nor
writing. It could be that the 6.6 you have achieved is still doable, but my 8.4
is not. so setting MESH to 7 or 8 may be a safer fast speed. havent tried it
though.
I didn't know you could set it at some speed in between - I rather thought
these were basically two different settings, with 5 or 10 MB/s being the
nominal transfer rate, and actual transfer rating below that. According
to dmesg my Orb drive is found and communicated at 10MB/s, thus the 6.6
(as the 3.3 in the slower mode) would seem to be limited by the controller.
I always heard the Mac SCSI controllers were quite slow, 3-3.5 MB/s being
a common rate for the external bus. The continuous r/w performance of the Orb
itself is much higher, ~ 12 MB/s. For real world performance, I'm getting
about 4.5 MB/s read/write on larger files (in fast mode).
I had some problems with the drive initially, but they also occured with
the driver set to slow mode, and mostly seem to have settled now.
But maybe this is a safe setting only for HD devices, as I frequently hear
that you shouldn't mix HDs and CDROMs, scanners etc. on one chain, the
latter seem to tend to have worse SCSI implementation.
Thanks,
Derek
--
Derek Homeier Tel: +49-431-880-4103
Institut fuer Theoretische Physik und Astrophysik Fax: +49-431-880-4100
der Christian-Albrechts-Universitaet Feet: Room 142
D-24098 Kiel, Germany email: homeier@astrophysik.uni-kiel.de
-----------------------------------------------------------------------------
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
From: Joseph Garcia <hidden> Date: 2000-03-23 19:18:53
Derek Homeier wrote:
I didn't know you could set it at some speed in between - I rather thought
these were basically two different settings, with 5 or 10 MB/s being the
nominal transfer rate, and actual transfer rating below that. According
I'm not sure myself. never tried it. ^_^;
to dmesg my Orb drive is found and communicated at 10MB/s, thus the 6.6
...
that you shouldn't mix HDs and CDROMs, scanners etc. on one chain, the
latter seem to tend to have worse SCSI implementation.
Thats interesting. I will have to try that some time. Right now, my chain has
the CDRW after the Syquest, and I never figured in the potential sync problems.
However, I recall one of my friends mentioning that 10M/s should not be possible
because the compact connector on powerbooks is missing those extra 12 or so pins
needed. Maybe the Orb is reporting 10, but falling back or compensating for the
lack of pins. Or maybe connectors have changed. My chain's Syquest has a
Centronix connector, my RW has a 50 pin mini-trapezoid. Could explain some
things. Whatever works i guess.
--
Joseph P. Garcia jpgarcia@execpc.com jpgarcia@lidar.ssec.wisc.edu
CS Undergraduate Student Employee - Systems Programmer
University of Wisconsin - Madison UW Lidar Group
"Ask yourself, Why do you seek the developer kernel? Is it for its glory,
or for yours?"
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
From: Michel Lanners <hidden> Date: 2000-03-24 07:01:28
Hi all,
On 23 Mar, this message from Joseph Garcia echoed through cyberspace:
Derek Homeier wrote:
quoted
I didn't know you could set it at some speed in between - I rather thought
these were basically two different settings, with 5 or 10 MB/s being the
nominal transfer rate, and actual transfer rating below that. According
That's my understanding as well. The 5MB/s or 10 MB/s is the raw byte
througput of the SCSI bus; for net rate, you have to count driver
overhead, command overhead, idle times on the bus, disk slowness, etc...
quoted
to dmesg my Orb drive is found and communicated at 10MB/s, thus the 6.6
...
quoted
that you shouldn't mix HDs and CDROMs, scanners etc. on one chain, the
latter seem to tend to have worse SCSI implementation.
Thats interesting. I will have to try that some time. Right now, my chain has
the CDRW after the Syquest, and I never figured in the potential sync problems.
On my 7600's internal MESH, I had both hard drives (sync at 10MB/s) and
the factory-installed CDROM (sync at 5MB/s) and never had any
particular problem. SCSI host adapters do negotiate separate parameters
per target; that's how you can mix narrow and wide devices on one bus,
by the way.
However, I recall one of my friends mentioning that 10M/s should not be possible
because the compact connector on powerbooks is missing those extra 12 or so pins
needed. Maybe the Orb is reporting 10, but falling back or compensating for the
lack of pins. Or maybe connectors have changed. My chain's Syquest has a
Centronix connector, my RW has a 50 pin mini-trapezoid. Could explain some
things. Whatever works i guess.
No, no, there's nothing with pin count involved here. Macs have always
had narrow buses (i.e. 8bits wide), and the difference in pin count of
the connector is compensated by having different numbers of ground
pins. On good cable material, this should have no influence on
throughput.
On 23 Mar, this message from Dan Bethe echoed through cyberspace:
I second the question. And what does "safe" mean? Could these
aggressive settings damage your data, your hardware, or both? If it's
just data, then that's okay for me to try. I'll turn it off when I
find corrupted data.
Setting the speed too high might corrupt data, but will never damage
hardware. As stated above, host and target negotiate a compatible set
of settings; this should already guarantee valid data transfers. The
reason Apple states 5MB/s as limit for external buses is to depend less
on the quality of the cables involved, and to permit longer chains
conneting many external devices. Think 'hassle-free plug&play'....
Michel
-------------------------------------------------------------------------
Michel Lanners | " Read Philosophy. Study Art.
23, Rue Paul Henkes | Ask Questions. Make Mistakes.
L-1710 Luxembourg |
email mlan@cpu.lu |
http://www.cpu.lu/~mlan | Learn Always. "
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/