From: newbie@hendrix.camb.inmet.com (Chris Newbold)
Subject: Re: Smartdrv vs Built-In Cache
Organization: Intermetrics, Inc.
Date: Mon, 27 Jul 1992 19:51:04 GMT

In article <0095E1C5.3BDE0260@vms.csd.mu.edu> 5916rahmank@vms.csd.mu.edu writes:

...

>
>		Smartdrv.exe loaded (w/double buffer)		Not loaded
>                -------------------------------------		----------
>1. Time to load win 3.1:		29:00 sec		36:27 sec
>
>2. Time to load W4W 2.0a:		8:23 sec		12:46 sec
>
>3. Time to load a 2.11MB file						
>   in W4W. This file has						
>   lots of graphics in it:		3:82 sec		4:10 sec
>						
>4. Time to save the same file:		16:17 sec		19:10 sec
>
>5. Time to load excel 4.0:		8:29 sec		11:14 sec
>
>The system used is:
>	486DX2 running at 64MHz (with 256k external cache)
>	16Meg RAM
>	DTC SCSI (EISA) controller with 512K on board cache
>	Maxtor 333MB Hard drive with cache 
>	Diamond SpeedSTAR w/1MB VRAM.
>
>	This experiment shows that when smartdrv.exe is loaded it saves time 
>i.e., the system performs much better than when it is not loaded. This 
>difference in time (which translates to the performance of the system) becomes
>more prominent with systems with lower clock speed. However, the main question
>here is smartdrv vs. built in cache. It would be interesting to perform similar
>time measurements on other systems and then make a comparison. But still the
>question remains: why smartdrv enhances performance even though there is
>built-in cache on the drive (as well as on the controller)? 

Ah. But how big was the SMARTdrive cache? Something like 2-4MB, I'll bet.
The 512K cache on the controller is trivial by comparision.

I have a setup similar to the one above. It used to have 512K on the DTC.
I tried similar experiments with a 1MB SMARTdrive cache on top of the 
harware cache. There was a similar significant speed improvement.

However, I have finally got 2MB on the controller (what I ordered; they put
the wrong SIMMs on the controller :-(... With 2MB hardware cache the system
is just as fast as with the 512K hardware cache PLUS the 1-1.5MB SMARTdrive
cache.

I think the results above speak more about the SIZE of the cache used than
the TYPE (hardware or software).

The real experiment would be to compare a 2MB SMARTdrive cache against a
2MB hardware cache. Unfortunately, I don't think the DTC will run without
RAM installed...

The other lesson I learned from all of this fooling around is that defragging
your hard disk will provide significant speed increase. At least with the
DTC controller, there is software-configurable read-ahead. I have mine set
so that if there are two or more requests for data in a linear fashion, the`
controller reads the next several tracks into the hardware cache. Result?
Windows loads in about 20 seconds. With even a minimally fragmented disk,
the read ahead is defeated because there is no way to predict where the
next data will need to come from.

-Chris


-- 
---- Chris Newbold ---- > "If you fool around with a thing for very long you <
   Intermetrics, Inc.	>  		  will screw it up."		     <
  Opinions and statements expressed are MINE and do NOT represent my employer
			newbie@inmet.camb.inmet.com
Newsgroups: comp.os.ms-windows.setup