From: newton@cs.utexas.edu (Peter Newton)
Newsgroups: comp.sys.mac.hardware
Subject: Review of LogiCache IIsi cache card with measurements
Date: 13 Oct 1992 19:32:16 -0500
Organization: CS Dept, University of Texas at Austin
NNTP-Posting-Host: mohawk.cs.utexas.edu

I recently purchased a LogiCache IIsi 64KB unaccelerated cache card
for my Mac IIsi.  I thought a review with performance measurements
might be of interest.

Summary:
  Product: Logicache IIsi
  Source:  Third Wave 800-448-0404
  Price:   $149
  SpeedUp: 1.22 on a set of real applications
  Overall: Works with all software I have tried.
  Date of Review: 10/7/1992

The LogiCache IIsi is an unaccelerated cache card, it contains no
processor.  All it does is provide fast cache memory.  The
documentation claims that a cache hit is four times faster than a
regular memory access.  I was told by Third Wave that the memory is
25ns static RAM.  It's a mixed cache, of course. I know nothing more
about its design. 

The card plugs directly into the slot in the IIsi.  No adapter card is
needed.  It does not contain an FPU or even a socket for one.  An FPU
can be added by buying a dual slot adapter ($59) and plugging the
cache and coprocessor into that.  The adapter has a socket for the
FPU.  This leaves a PDS slot free.  I have neither a dual slot adapter
nor an FPU.

Installation is trivial-- literally a snap.  A CDEV is supplied that
permits the cache to be turned on and off.  It can also trap SANE
calls to an FPU, if you have one.  I have had absolutely no problems
with the software, and I have yet to encounter a compatibility problem
with the cache card. 

The purpose, of course, is to make the Mac faster.  Advertisements
claim speedups of up to 40%.  Actual speedup depends on what program
you measure, and is rarely as good as 40%.  Results vary *widely* from
application to application.  On a set of real applications, I measured
an average speedup of 1.22.  The numbers are listed below, along with
Speedometer results.  The cache card appears to do best with graphics
and mathematical computations.

I would like to hear from anyone who has measured an unaccelerated
cache card doing better.  My guess is that they are all about the
same.  Advertisements claim 30% - 45% improvement.  Reality is
closer to 25% on average with real applications.

I would guess that a cache card would significantly reduce the
performance hit from running out of the dual-ported RAM on the IIsi,
but I have not measured this.  This might be of interest to people who
use virtual memory since virtual memory defeats the disk cache
anti-dual-ported RAM trick.  I use a disk cache large enough to avoid
running out of the dual-ported RAM, and I have virtual memory turned
off.

Should you buy one?  It's hard to say.  On one hand, the speedup is
really not very great.  On the other hand it is probably the cheapest
add-on to speed up the IIsi, in terms of "MIPS" per dollar or some
such measure.  It's like *adding* the power of a Classic to your IIsi
for $149, but do you care about the added power of a Classic?

If you have less than 5 MB of RAM, buy RAM instead.  Turn off virtual
memory and set your disk cache large enough to avoid running apps out
of the dual-ported RAM.  (How large depends on your extensions.  768K
is certainly enough).  If you are really unhappy with IIsi
performance, save your money for an accelerated card or a new Mac.

Measurements are made on a 5MB IIsi with tuned System 7.0.1.  The disk
cache is set large enough to avoid running apps out of the dual-ported
RAM.  Virtual memory is off.  32 bit mode in on.  Some measurements
are more accurate than others.  I run with 256 colors all the time.
The disk used in some cases is fairly slow (Seagate ST-157N).  Times
are in seconds.  An * means little or no disk involved.

     Program              No Cache  With Cache Speedup
GifConverter GIF Open:       7.6      7.0      1.09
Otter Theorem Prover:*      24       19        1.26
Ephem Astro Calc:*          10.85     8.33     1.30
Compact Pro folder compact: 33.2     27.8      1.19
Think C Compile:            66       52        1.27
DialScript Listing:*        25.42    20.24     1.26
Framemaker scroll:*         12.14    11.5      1.06
AstroBench:*                19.98    14.54     1.36
Gravity Simulator:*         16.6     12.03     1.38
Framemaker file open:       21.23    18.29     1.26

      Speedup mean = 1.23, harmonic mean = 1.22.

I also did Speedometer runs both with and without cache.  It is not
clear how many of Speedometer's results are really meaningful since
little benchmarks can fit entirely within the cache.  The "CPU" result
is really strange.  I wonder if that one is so small that it fits in
the 68030's tiny on chip caches.

Speedometer 3.1 Results:    No Cache   With Cache

P.R. Results (Uses Mac Classic as 1.0)
   CPU:                      5.509       5.598
   Graphics:                 6.672       8.107
   Disk:                     1.925       1.908
   Math:                     5.604       7.633
   Performance Rating (PR):  5.151       5.816
   
Benchmark Results (Uses Mac Classic as 1.0)
   KWhetstones:              6.737       9.081
   Dhrystones:               5.097       6.133
   Towers:                   4.727       5.522
   QuickSort:                5.099       5.722
   Bubble Sort:              6.183       6.279
   Queens:                   6.189       6.361
   Puzzle:                   6.625       7.123
   Permutations:             5.434       5.772
   Fast Fourier:             4.496       6.222
   F.P. Matrix Multiply:     4.735       6.694
   Integer Matrix Multiply:  5.394       6.465
   Sieve:                    6.896       6.947
   Benchmark Average:        5.634       6.527
   
Color Tests (Uses Mac II as 1.0)
   Black & White:           1.755       2.164
   4 Colors:                1.906       2.311
   16 Colors:               2.016       2.401
   256 Colors:              1.282       1.742
   Color Test Average:      1.740       2.155
-- 
 ----
Peter Newton (newton@cs.utexas.edu)