24 Jun
2009
24 Jun
'09
7:06 a.m.
--- On Tue, 6/23/09, Paxton Hoag <innfoclassics at gmail.com> wrote:
Hmm, I didn't change any of the jumpers on the card, I'll have to check those when
I get home. I assume this just changes the controller to work with an AT BIOS?
WX-1 is 2 MFM hard drives only, WX-2 is hard drives
plus
two floppys.
My CSC Hard Drive manual says it is an 8 bit contoller for
two hard
drives. To format use G=C800:5 (Why is
that so familiar!!!)
OK, that makes sense. I ended up just using the WX-1 because I was familiar with it. I was
able to format the drive from debug no problems, and the Compaq boots from it, despite not
using the Compaq setup program.
From the book
the default jumpers on the WD 1002A-WX1
are
W3,W4-2 & 3, W6-2 & 3, W8-2 & 3, S1-8 (AT
Mode) I think you will need the compaq set up disks. I still
have
a set but
not sure where they are. I might be able to locate them if
you need me
to.
A kind listmember is already sending me a copy. I found _a_ setup program, but it's
clealy not the one for this computer. At least I was able to change the time and date, but
it's options for the hard disk were really limited. Right now I just have the
'fixed disk' disabled in the setup. The Compaq boots just fine from the controller
as it is now.
I think an interleave of 3 would be OK as it is an XT
class
controller. But, as mentioned, Spinrite can optimize it for
you. The
nec drive is an AT class drive at 28 ms. It should work
fine.
It does work, I just wonder if changing the interleave could make it any faster. I mean,
the computer isn't particularly fast in any case, but anything to improve hard disk
performance is a good thing. Do you have a version of Spinrite that will work? I was only
able to find version 6.0 on the internet, and it won't even load on the 286. Just
hangs.
-Ian
24 Jun
24 Jun
7:43 a.m.
On Jun 24, 2009, at 10:06 AM, Mr Ian Primus wrote:
It does work, I just wonder if changing the interleave
could make
it any faster. I mean, the computer isn't particularly fast in any
case, but anything to improve hard disk performance is a good
thing. Do you have a version of Spinrite that will work? I was only
able to find version 6.0 on the internet, and it won't even load on
the 286. Just hangs.
I know you were asking Paxton, but I *might* be able to find my
old copy, I will look.
Setting the interleave properly for your particular model of
controller can result in significant data transfer rate
improvements. Setting it too low can slow things down a *lot*. The
best controllers, of course, will handle 1:1 interleave (a.k.a. "no
interleave").
-Dave
--
Dave McGuire
Port Charlotte, FL
8:23 a.m.
On 24 Jun 2009 at 10:43, Dave McGuire wrote:
Setting the interleave properly for your particular
model of
controller can result in significant data transfer rate improvements.
Setting it too low can slow things down a *lot*. The best
controllers, of course, will handle 1:1 interleave (a.k.a. "no
interleave").
I've always been a little peeved at the disk drive utilities that
determine "optimum" interleave for an AT-style MFM controller.
There are really two dimensions to the problem--and no interleave
"optimizer" that I know of deals effectively with them.
The first, of course, is how fast your PC and controller can get data
off of a drive. Choosing a too-small interleave can have disastrous
effects on performance because you can get to the point where only a
single sector per rev is being transferred. A too-large interleave
has a much lesser effect on performance, since the PC is waiting only
a sector time or two to get the next sector. In other words, on may
not notice a large subjective difference in performance if the
interleave is at 4:1 instead of 3:1.
The other aspect of the problem is how fast an application can read
data--that is, how much processing is going on between disk accesses.
Setting the interleave to a value that an optimizer comes up with can
have the same effect as a too-small interleave. That is, the
application must wait a whole revolution before data is available.
Some old CP/M systems used three interleaves (I've got at least one
sample of this in my collection). The boot tracks are formatted with
a 1:1 interleave, as they're simply streamed into memory with no
processing; the directory area is formatted at 2:1 because directory
searches aren't usually processor-intensive and the remainder (data
area) of the disk is formatted at at 3:1.
Ultimately, the solution is a controller with a large buffer or cache
or a cache driver in the PC. Then the controller essentially becomes
the limiting factor and the "optimum" interleave determined by a
utility is essentially the correct one, since reads are occurring a
track at a time.
But for non-cache, sector-at-a-time setups, it's better to choose an
interleave that's slightly larger than recommended.
Similarly, if a controller can support multi-sector reads at unity
interleave, it makes sense to interleave clusters rather than
sectors.
FWIW,
--Chuck
12:10 p.m.
On Jun 24, 2009, at 10:06 AM, Mr Ian Primus wrote:
It does work, I just wonder if changing the interleave could make it any faster. I mean,
the computer
isn't particularly fast in any case, but anything to improve hard disk performance is
a good thing.
The optimal situation is that you have a controller that can handle
1:1 interleave (i.e., "none" - the sectors are in sequential order
around the track) and a machine that can keep up with that sustained
transfer rate. Where interleave comes into play is if your controller
and/or host is too slow to keep up with one sector after another, so
the sectors are staggered to give the machine time to be ready to
transfer the next block as it's about to pas s under the read head.
The worst case is when your interleave is too "small" for your system,
the next block passes under the head before the system is ready to
handle it, and the system has to wait a full revolution of the disk
for the next pass.
Since someone else mentioned "28ms", it minds me to mention there are
two sets of delays that are now usually grouped together... one is
seek time, which is what 28ms is one measure of, the other is
rotational latency, which is where the interleave factor comes into
play. No matter what your interleave factor, if your drive is rated
at "28ms average seek time", it will take that long to move the head
in and out to the right track. Once the disk is on track, because
it's going to be over a random sector, the average rotational latency
is half the time it takes the disk to spin once - which is why there's
such a push for 10K and 15K drives now (in the old days, 3600rpm was
doing pretty good). _On top of that_, interleave is part of what
determines how long it will take to get to the second then the third
then the fourth sectors on that track.
So if your interleave is badly matched for your machine and disk
controller, you may see some poor sustained transfer rates, but if
it's only a little off, you'll gain back some lost performance, the
amount of which is largely dependent on your disk speed (slow disks
mean better performance recovery, but you still have a slow disk, thus
high rotational latency to begin with).
ISTR a certain obsession with this amongst DOS users back in the day,
but perhaps that was because it was reasonable to expect your files to
be somewhat linear on disk and because hardware performance varied so
widely. Over in the DEC world, you pretty much got what you got, and
with the exception of the RM02/RM03 differences (different rotation
speeds for different systems that could handle different amounts of
disk throughput), we didn't obsess about drive performance minutiae
except when were deciding what disk to buy next.
-ethan
5612
days inactive
5612
days old
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