From: 5916rahmank@vms.csd.mu.edu
Newsgroups: comp.sys.ibm.pc.hardware
Subject: ..SMARTDRV vs Built-in Cache, built-in is faster!....
Date: 22 Aug 92 18:48:22 GMT
Article-I.D.: vms.0095F799.3AEAA180
Reply-To: 5916rahmank@vms.csd.mu.edu
Organization: Marquette University - Computer Services

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
|>
|>	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			newbie@inmet.camb.inmet.com

==========================================================

    Hi Folks:
	Finally I got 4M ram on my DTC SCSI card and I ran the
	smartdrv vs. buitl-in cache experiment again. And yes,
	built-in cache is faster than the smartdrv cache!

(a)	Here is one comparison. It took 29:00 sec to load the NDW
	along with lots of icons (win 3.1) when I tested with
	512K built-in + 1mb smartdrv cache (as I reported before).

(b)	With 4mb cache on the card it takes only 12:12 sec! (no smartdrv).

(c)	According to previous discussions in this thread, built-in
	+ smartdrv should be slower than the built-in cache alone. 
	This is precisely what I found, it took 22:00 sec to load 
	NDW and everything with the 4mb built-in + 2mb smartdrv!

	So now, there is no contradiction between theory and experiment!

	These tests were done on a stacked drive, so results may be
	different on an unstacked drive.

	- Anis, Dept. of EECE, Marquette University.
Newsgroups: comp.sys.ibm.pc.hardware