Re: Apple IIc+ & Memory

[supertimer@aol.com (Supertimer)]

hlevinsn@andromeda.rutgers.edu (Hank Levinson) wrote:

>buggie@ben06.unm.edu (stephen e buggie) writes:
>
>>The IIC PLUS can accept the RAM EXPRESS one meg ram card.  I have it, but
>>its not for sale.    Nice graphical screen on the RAM EXPRESS self-test
>>disk.
>
>>Speed of the IIC PLUS is 4 MHz unless it is slowed down at power-on.
>
>>Normally, you run it at 4 MHz except for games.
>
>>Steve Buggie			buggie@unm.edu
>
>	Since I posted that the speed of a IIc+ is about 3.6 Mhz, and Prof.
>Buggie stated it ran at 4 Mhz, I decided to try to find out exactly how a
>IIc+ compares to a IIc. I had both run a simple counting program
>simultaneously. I supposed that the IIc+ would get to 36,000 or 40,000 in
>the time it took the IIc to count to 10,000. The results were surprising.
>
>		10 HOME: N = 1
>		20 N = N + 1: GOTO 20
>
>	   after 10 hours, the IIc had counted to 10,683,218 and the IIc+ to
>35,958,758. 35958758/10683218 = 3.36591, slower (!!!) than the longer program.
>
>	I conclude that calls to the BASIC interpreter, which translates each
>line to machine language, executes it and then goes to the next line (the same
>line in this case; GOTO 20), may have also slowed down the IIc+ from its
native
>speed. On the other hand, these calls should have been executed at the IIc+'s
>faster speed and it shouldn't have made any difference in relative speeds of
>the two machines.
>
>	However, it seems to me that the IIc+ goes at a speed of closer to 3.6
>Mhz than to 4 Mhz. There is indeed a 16 Mhz crystal in the IIc+, but does it
>clock the machine or does it synchronize output to the monitor as the early
>PC's do? I remember seeing somewhere that the IIc+ ran at 3.6 Mhz, but I fail
>to remember exactly where I saw this.
>
>	If anyone can devise a test to show the IIc+ runs 3.6 (or 4) times
>faster than a IIc, please let me know. All this raises the question of "How
>fast does a machine go?" Do we simply measure the speed at which its CPU chip
>is clocked, or shall we see how fast it executes a program? (I once had a car
>whose speedometer was capable of reading 160 mph.; luckily I never attempted
>it!)
>
>H. Levinson   hlevinsn@andromeda.rutgers.edu

Hi.  The IIc Plus does indeed run at 4Mhz.  Or rather, the CPU
runs at 4Mhz.  Let me explain:

The IIc Plus has a 1Mhz motherboard because that's the way
Apple originally intended it to run.  However, just before the
IIc Plus was released, Video Technologies of Hong Kong was
getting ready to release the Laser 128EX/2, a computer built
from the ground up to run at 3.6Mhz.  The 128EX/2 is a TRUE
3.6Mhz computer in that its motherboard runs at 3.6Mhz.
Apple needed a way to turn the IIc Plus into a more powerful
computer fast in order to compete (if you look at the 128EX/2
and the IIc Plus, you'd know why they were competitors...both
had 3.5" internal drives, for one thing, and both were semi-
portable units).

It just so happens that Zip Technologies of Culver City,
California was selling a caching accelerator for the Apple II
(8-bit models).  It was called the ZipChip.  At the time,
it ran at 4Mhz (later units ran at 8Mhz).  Bingo, Apple
thought, so it went into negotiations with Zip.  Zip wanted
to sell Apple real ZipChips to plug into the IIc Plus, but
Apple would have none of it.  So in the end, Apple paid
an undisclosed sum of money to license Zip's patented
caching technology.

Apple then went to work.  Scattered over the motherboard
of the IIc Plus is the equivalent of a 4Mhz ZipChip. Namely,
8k of cache RAM, some custom (Zip Technology) logic
chips, a 4Mhz 65C02 and the 16Mhz oscillator.

Now on the surface, the 4Mhz IIc Plus SOUNDS like it
can beat a Laser 128EX/2, but can it really?  It depends,
it turns out.  Remember, the speed depends on both
the motherboard and the CPU speed just as in the PC
world.  An AMD K6-III operating at 450Mhz is blazing
fast, but the motherboard is operating at only 100Mhz.
In the IIc Plus' case, the motherboard was operating at
1Mhz while the CPU was operating at 4Mhz.

The 128EX/2 can always run fast while the IIc Plus
must slow down to 1Mhz at times to get data into and
out of the 8k of cache RAM.

That's why your program yielded sub-4Mhz speeds.
Different programs yield different results.  The BASIC
interpreter does not show the IIc Plus in the best light.
I think the tests that really gets close to the 4 to 1
performance expected from a IIc Plus relative to a IIc
is calculations in an AppleWorks Classic spreadsheet
or word counts in AppleWorks Classic word processor.
AppleWorks Classic seems to show off the ZipChip
acceleration quite well, probably because the internal
code is in very small chunks.