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BigEd
PostPosted: Sat Mar 12, 2022 1:01 pm 
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Some usenet posts suggest that in 1991 WDC were selling -7 and -8 versions of '816.
Quote:
what you will get is a hand-picked part from an 8 mhz shipment that does in fact run at 10 Mhz with the standard 5 volts. I have one running at 10 and it says 8 on the chip

Also
Quote:
The highest speed I've heard of that seems
to be reliable is 10MHz. One can get 65816 chips from WDC, in SMALL
quantities, that are certified for operation at high speeds; they come
with a so-called Shmoo plot delineating the range of speed vs. applied
Vcc. For speeds above 9MHz, you almost always have to crank up the DC
power supply above the nominal 5V level, perhaps as high as 6V. This is
not something to be done lightly

Of course I'd rather see something more official or definitive. I'm not primarily interested in overclocking.

Also to note, there's talk at around the same time of an independently designed and implemented ASIC '816 which was hoped to reach 20MHz or more. Similarly, not quite the thing for this thread, more of a red herring. (And, again, the Mac IIfx used two '02 cores at 10MHz, but these were custom or semicustom chips, not standard parts.)
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BigEd
PostPosted: Sat Mar 12, 2022 1:39 pm 
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Snippets from a July 1993 FAQ ("mini-FAQ: upgrading TransWarp GS/Zip GS"):
Quote:
- Should I buy the Sanyo chips? Or WDC ones?
Sanyo re-engineered the 816, but WDC sells them.

- Where can I purchase the high-speed 65816 from?
The Western Design Center, Inc.
...
Each hi-speed 816 is individually tested. All hi-speed 816 are designed to do 12mhz @ stock 5v.
...
- do I really need to increase the voltage?

You can learn to read your shmoo plot by reading the article
sent by WDC. In my case, I was suppose to supply 4.75v - 5.25v
to run at 12.82mhz, 5.5v - 5.75v for 13.51mhz, and 6v for
14.71mhz.

But I'm suppling 5v @ 13.75mhz, and about 5.2v @ 15mhz. Your
requirement might be different.


An update posted in September notes "I'm told they don't require you to get a copy of the article anymore"

And from a September 1996 FAQ (
Frequently Asked Questions (FAQ) for upgrading GS accelerators):
Quote:
Does it really run at 14 MHz?

WDC now has true 14 MHz parts, they will run 14 MHz at the stock 5 V.
It is possible because of the 0.8 micron chip fabrication process.
(formerly 1.0 micron I believe)

If you run it with 5+ volts, higher speeds should be possible.

Note: Apparently, WDC does not warrent these new 14 MHz chips even
though they are production parts. This sucks because the chip I have
does not work correctly even at 12.5 MHz.


But we can get closer - this Feb 1995 update ("Final (?) update to TWGS/Zip GS Mini-FAQ") contains the above snippets and more:
Quote:
08-22-94 - Major update, availability of true 14 MHz parts!!
...
Price: $19.80 each, minimum order is $100

Availability: shipping now!

Note: All of the chips have been tested to run 14 MHz at 5 volts. Thus the schmoo plot sheet isn't included any more.
...
** ~~9. Do I really need to increase the voltage?

With the new 14 MHz parts, you should not need to mess with the
voltage at all. Unless you want to try 15 MHz, 16 Mhz, or
even 20 MHz.


So, by August 1994 WDC have started selling 14 MHz parts to hobbyists without need for overvoltage but also without warranty.
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Arbee
PostPosted: Sun Apr 03, 2022 4:14 am 
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Just wanted to clarify a few points here, based on the current knowledge of Apple II enthusiasts. The IIgs didn't run at 2.8 MHz to protect the Macintosh, it ran at that speed to protect Bill Mensch. The original kitchen-table mask for the 65C816 had certain opcodes (REP, SEP, and I think XCE) fail to complete in the available cycle time as you got closer to 4 MHz. The IIgs hardware designers have verified this - they initially planned to run at 7.16 MHz, the same as the contemporary Mac, but the 65C816 in 1986 wasn't even close to capable of it. 3.58 MHz would've been possible with the GS's clock structure (everything's an integer divisor of the venerable 14.31818 MHz crystal) but they were afraid some parts would be marginal even at that speed.

The TransWarp GS had complex logic to sniff the instruction stream and dynamically reduce the clock when it saw one of the affected opcodes coming in. The Sanyo redesign made that unnecessary, which is one reason the later ZipGS was a much simpler design.
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Dr Jefyll
PostPosted: Sun Apr 03, 2022 4:38 am 
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Welcome, Arbee, and thanks for posting.

I wasn't aware of the cause & effect implications re IIgs clock speed, but I have heard that early 65C816's had trouble with REP and SEP. I don't have any links or references to offer but maybe you or someone can supply us with further info on this interesting situation.

-- Jeff

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GARTHWILSON
PostPosted: Sun Apr 03, 2022 5:10 am 
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Arbee wrote:
Just wanted to clarify a few points here, based on the current knowledge of Apple II enthusiasts. The IIgs didn't run at 2.8 MHz to protect the Macintosh, it ran at that speed to protect Bill Mensch. The original kitchen-table mask for the 65C816 had certain opcodes (REP, SEP, and I think XCE) fail to complete in the available cycle time as you got closer to 4 MHz. The IIgs hardware designers have verified this - they initially planned to run at 7.16 MHz, the same as the contemporary Mac, but the 65C816 in 1986 wasn't even close to capable of it. 3.58 MHz would've been possible with the GS's clock structure (everything's an integer divisor of the venerable 14.31818 MHz crystal) but they were afraid some parts would be marginal even at that speed.

Welcome.

I have read that early 816's needed a NOP after a few of the op codes if you run at the the higher speeds, but that otherwise there was no problem running at those higher speeds.

http://www.apple-iigs.info/histoire.php says (in French, later the translation):

    Pour ce qui est de la vitesse du processeur, le choix d'une vitesse maximale de 2,8 MHz qui a été fait au moment de la conception correspondait autant à un choix commercial qu'à un choix technique. Du point de vue technique, le processeur pouvait monter sans peine jusqu'à 16 MHz mais le fournisseur, par manque de moyens de test adaptés, ne le certifiant que jusqu'à 4 MHz, Apple de prendre une fréquence de base pour le processeur inférieure à cette certification. Du côté commercial, le vrai problème était que chez Apple, le nouvel Apple IIGS risquait de concurrencer, avec une vitesse de processeur plus importante, le Macintosh qui, à l'époque, ne disposait pas encore d'écran couleur et dont la résolution graphique et surtout sonore était loin d'égaler celle de l'Apple IIGS. Cette vitesse maximale de 2.8 MHz resta, tout au long de la vie commerciale de l'Apple IIGS, une véritable lacune pour la machine; ce qui explique en grande partie le succès des cartes accélératrices qui furent proposées par des fournisseurs autres qu'Apple (ZipGS et Transwarp GS par exemple). Toujours au niveau de la vitesse du processeur, une particularité de l'Apple IIGS réside dans le fait qu'en mode émulation, le processeur est capable de fonctionner à 1 MHz.

translation:

    In terms of processor speed, the choice of a maximum speed of 2.8 MHz which was made at the time of design corresponded as much to a commercial choice as to a technical choice. From a technical point of view, the processor could easily go up to 16 MHz but the supplier, for lack of suitable test means, only certifying it up to 4 MHz, Apple to take a lower base frequency for the processor to this certification. On the commercial side, the real problem was that at Apple, the new Apple IIGS risked competing, with a higher processor speed, with the Macintosh which, at the time, did not yet have a color screen and whose graphics resolution and especially sound was far from equaling that of the Apple IIGS. This maximum speed of 2.8 MHz remained, throughout the commercial life of the Apple IIGS, a real shortcoming for the machine; which largely explains the success of the accelerator cards that were offered by suppliers other than Apple (ZipGS and Transwarp GS for example). Still in terms of processor speed, a particularity of the Apple IIGS lies in the fact that in emulation mode, the processor is capable of operating at 1 MHz.

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BillG
PostPosted: Sun Apr 03, 2022 6:40 am 
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I have a Transwarp in an Apple IIe. It can be set to run at three speeds: 1 MHz, 1.7 MHz or 3.6 MHz. It has a socket for an optional 65C802; I do not have that. The manual does not warn against running an 802 at 3.6 MHz.
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