Accelerator 16 bit

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From: tdiaz-a(in_a_circle)-apple2-dotsero-org (Tony Diaz)
Newsgroups: comp.sys.apple2,comp.answers,news.answers
Approved: news-answers-request@MIT.EDU
Followup-To: comp.sys.apple2
Subject: Apple II Accelerator Frequently Asked Questions (FAQ)

Archive-name: apple2/accel
Posting-Frequency: monthly
Last-modified: Sept 20 2007
Version: 1.3

Mini-FAQ for upgrading TransWarp GS or Zip GS


Copyright (c) 1993-96, by Frank M. Lin, Nathan Mates, Tony Diaz All rights reserved.

Feel free to distribute original copies of this to anywhere you think it might be of help. However, I'd like to keep a master version of this document available at, so I'd much appreciate it if you made links to this page than duplicating it.

I make no guarantee about any of the information provided below. If you choose to do any part of the upgrade, you are taking the risk. I will not responsible for anything.

Where can I buy the 32 KB cache for Transwarp GS?

///SHH Systeme, (Write to: SHH SYSTEME, Dipl. Ing. Joachim Lange, Bergstrasse 95, 82131 Stockdorf, Germany) is now making a 32K cache addon board for TWGS boards. You may wish to contact them and check on pricing and availability.

[It used to be available from LRO Computer Sales (800) ASK-4LRO, with price about $80. It requires you to cut two little traces at the back of TWGS. Cut it _lightly_, it's fairly easy to cut too deep. So just take it easy. Note: Not too sure if LRO exists; I know they are around, under a different name. Do they deal with Apple II stuff anymore? If you have the old TWGS (with 8 KB cache, and/or older GALs), you should look for a new or used Zip GS.]

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.

Toshi Morita's new chip doesn't work at all! I'm not that much better neither since the chip isn't worth anything if it isn't stable. Heck, my older engineering sample crashes less.

Couple of others have reported good success with the new parts though, so I'm just noting that you may get a bad chip!

Others have suggested that it isn't actually a bad chip. It's just a chip with lower environment tolerance compare to other chips. So you may have to do additional modifications to the TWGS/Zip board to make it really stable.

Where can I buy the high-speed 65816?

Western Design Center has a WWW Home Page at if you want to contact them directly, or you can email them at directly. - Orders

If you prefer snailmail:
The Western Design Center, Inc.
2166 East Brown Road
Mesa, Arizona 85213

(602) 962-4545 voice
(602) 835-6442 fax

You can also purchase 65816 from

What GALs version do I need for my TWGS?

In theory, you have to have the following GALs to go over 10 MHz:

1A, 2B, 3E, 4B, 5A, 6A, 7A, 8B

All TWGS should have the A GALs. So you need:

2B - DMA fix 3E - for above 10 MHz operation 4B - dunno 8B - dunno

However, with the "Sanyo die '816" which is what you currently get from WDC, anything stamped -14 or greater, and/or having a WDC logo in the oval, not just letters, will be a Sanyo Die '816. All of these fixes for higher speeds were to circumvent CPU issues and you actually get the best performance using all A rev. GALs. -tdiaz

Where can I buy the GALs?

Where can I buy crystal oscillators?

Digi-Key Corporation

(800) 344-4539 voice

(218) 681-3380 fax

For TWGS and Zip GS, the crystal oscillators runs at 4 times the speed of the 65816.

For example, you need a 40 MHz oscillator to run a TWGS/Zip GS at 10 MHz.

From March/April 1995 Digi-Key catalog: price dropped by about 30 cents for the Epson's, no price change for CTS'.

   Epson America, Inc.: 1/2 TTL for TWGS

        Part No.        Frequency       Price ($)       TWGS speed
        SE1101-ND       32 MHz          3.30            8 MHz
        SE1102-ND       33.3333         3.30            8.3333
        SE1103-ND       36              3.30            9
        SE1104-ND       40              3.30            10
        SE1105-ND       42              3.30            10.5
        SE1106-ND       46              3.30            11.5
        SE1107-ND       48              3.30            12
        SE1108-ND       50              3.30            12.5
        SE1109-ND       55              3.30            13.75
        SE1110-ND       60              3.45            15

   I have the CTS oscillators, 64, 66.6, and 80. So they will work fine with TWGS.
        CTS Clock Oscillators: 1/2 TTL for TWGS
        Part No.        Frequency       Price ($)       TWGS speed
        CTX174          32 MHz          3.25            8 MHz
        CTX175          40              3.25            10
        CTX177          64              4.45            16
        CTX178          66.6666         4.45            16.6667
        CTX179          80              10.01           20

Orders under $25 costs $5 to ship, over $25 is free..

My understanding is that, if you over clock a CPU. It just won't function. You can't damage it. As the disclaimer said, do it at your own risk.I have tried to run my TWGS at 20 MHz, system won't boot at all. No damage.

for Zip you need: (by Long)

The Zip can use three types of crystals including the common 4-pin full TTL crystal oscillator, 4-pin 1/2 TTL crystal oscillator (also used on TWGS) and 2-pin crystal (little metal canister about 1/4 the size of 1/2 TTL). To be able to use a 2-pin crystal, your Zip must have a resistor at R1 and capacitors at C13 and C14. I've found these three parts to be missing from current Zips. No big loss since 2-pin crystals are less common and are only available up to a certain frequency. I have the values of those parts written down somewhere and will post them when I find them.

For experimenting with different frequencies it makes it easier if you install a socket for the crystal oscillator. It's also a good idea to secure it down with one of those zip tie bands. Only 6 of the 14 pins are used (picture A). The ground (GND) pins 1, 4 and 7 are connected together. The power pins 11 and 14 are connected together. Full TTL crystal oscillators use pins 1, 7, 8 and 14 (refer to picture B). 1/2 TTL crystal oscillators use the bottom four pine (4, 7, 8 and 14; picture C). Make sure it's oriented correctly with the corner (usually with a dot printed next to it) at about 11 o'clock.

  • WARNING* The crystal oscillator will be damaged if installed incorrectly.
        GND  1 o  \/  o 14  POWER     1 |o      \  14
        NC     x      x     NC          |        |
        NC     x      x     NC          |  FULL  |           ______
        GND  4 o      o 11  POWER       |  TTL   |        4 |o     \  14
        NC     x      x     NC          |        |          |  1/2  |
        NC     x      x     NC          |        |          |  TTL  |
        GND  7 o      o  8  CLOCK     7  \______/   8     7  \_____/   8

                 (A)                       (B)                 (C)

        x - no connection (NC)

What speed of static cache RAMs do I need?

I have read 35ns is enough for 12.5 MHz. I'm not sure about the requirement of 13.75 MHz or 15 MHz. 15ns costs only slightly more than 20ns, so I recommand getting 15ns.

For TWGS with the 32 KB cache: 3 - 32 KB x 8 SRAM .3 mils (also called half size) try to get low-power models if possible.

for TWGS with older 8k cache: upgrade to 32 KB cache first. big speed improvements!

for Zip you need: (by Long)

<me, Frank: Zips uses wide SRAM (.6 mil) standard. You can use wide SRAMs if you can find them (they're harder to come by). Below, Long has a good illustration of how to make it accept wide or skinny (.3 mil) SRAMs>

I've found Japanese and American static rams to work the best (20 ns in tag and 25 ns in data). The Zip can use narrow (.3 mil) or wide (.6 mil) static rams. It all depends on the sockets that are installed on your Zip. With a little modification you can make a Zip with wide sockets accept both wide and skinny SRAMs. Ground yourself then carefully pry out the static rams. Look at the socket and you will notice two or three horizontal bars holding both sides of the socket together (picture D). Carefully cut those out. This will expose a column of holes where you will solder in half of a socket. Refer to picture E, position skinny (.3 mil) static rams over the left and center columns and wide static rams over outer most columns and making sure the notch on the static ram is facing 12 o'clock.

  • WARNING* Plug the static rams in wrong and you will destroy them.
            ___           ___________ Skinny (.3 mil)
           |   |         |   |
         ____ ____       _   _   _
        |o __V__ o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|__o__|o|     |o| |o| |o|
        |o _____ o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|  o  |o|     |o| |o| |o|
        |o|__o__|o|     |o| |o| |o|
        |o _____ o|     |o| |o| |o|

                         |_______|___ Wide (.6 mil)

            (D)             (E)

Toshi's ( notes: I've pulled out all four of my SRAM sockets and installed carefully cut machine-pin SIPP sockets in mine and seems to work pretty well.

Frank: Toshi's had to de-solder all the sockets and, so it isn't easier than Long's way. Toshi's came out looking cleaner and neater though.

Where can I buy the SRAMs?

The information here was from 1995, this being 2007- buying SRAMs nowadays means finding a surplus 486/586 board and grabbing them, for the most part. - also sells SRAMs for ZipGSX, TWGS

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.

How do I increase the voltage (with the heavy duty power supply)?

WARNING: generally, it's not recommended to do this. You might decrease the life of your GS. Adjusting the pot expose you to HIGH-VOLTAGES which can be FATAL!!! If you feel at all in-competent, it is recommended you stick to 5v, or let a qualified electrician do it ($$$).

Another reason is, performance increase from ~12 MHz to 13.75 or 15 MHz isn't as impressive as from 7 to 9/10 MHz, probably because the GS's 1 MHz bus limit. So it might not worth the risk/time/effort to try beyond 5v. You're also at a much higher risk of damanging your TWGS/Zip/GS.

Note: I've drove my GS to as high as 6 volts. Nothing blow up, except the computer just sorta reset it self. I don't recommend you to try this. :-) It's just a side note.

The easiest way would be to purchase AE's heavy duty power supply. Memory Plus Distributor (MPD sells the exact same supply (except without the AE sticker & price) for slightly cheaper. LRO also carries the MPD power supply.

The power connector on the mother board:

        |  _   _|
        | |_| |_        pin 1: ground
        |       |
        |  _   _|
        | |_| |_        pin 2: ground
        |       |
        |  _   _|
        | |_| |_        pin 3: no connection; not used
        |       |
        |  _   _|
        | |_| |_        pin 4: +5  volt supply
        |       |
        |  _   _|
        | |_| |_        pin 5: +12 volt supply
        |       |
        |  _   _|
        | |_| |_        pin 6: -12 volt supply
        |       |
        |  _   _|
        | |_| |_        pin 7: -5 volt supply

Attach the volt meter's gound to either gound pin, then the positive to the +5v supply. That should give a reading of 5v.

To turn up the voltage, simply open the HD (heavy duty) power supply. There is a pot (which you can turn with a screw) to adjust the voltage.

               ||      - power cord
        |           |
        |           |  ||  - 7 pin connector on your motherboard
        |           |  ||
        |           |
        |           |
        |           |
        |           |
        |oooooooooo =  - wires to your motherboard
        |oooooooooo |
        |oooooooooo |
        |oooooooooo |  - pot is located about 3" from the bottom &
        |oooooooooo |                   about 1" from the right
        |oooooooooo |
        |oooooooooo |       turn clock wise to increase the voltage
        -------------    counter clock wise to decrease the voltage

                         turn it SLOWLY!  supplying over 5.5v is not

If you have a skinny, long screw driver, you can adjust the pot with out opening the power supply. However, I think it's actually easier if you open it. Just don't touch anything but the pot.

Where can I buy a IIgs power supply?

Is it true that Zip can only go about 12.5 MHz?

The Zip need to have the 74F00 replaced with 74HC00. You might also need faster SRAM and additional voltage.

Where can I get replacement 7400 for my Zip?

Digi-Key Corporation (800) 344-4539 voice (218) 681-3380 fax --- National Semiconductor - 74HC00 Series CMOS (last updated 07-08-94) Digi-Key part number description chip package price MM74HC00N-ND quad 2-In NAND Gate 14-dip .28

What kind of performance increase can one expect?

This is just to give you a rough estimate of how much faster you might go...

        BenchMark v5.0 results:

        cpu         stock   twgs   twgs   twgs      zip    zip   zip
        version    ROM 01   1.8s   1.8s   1.8s    1.0.2  1.0.2  1.0.2
        cache/spd         32k/15 32k/15 32k/15   64k/?? 64k/?? 64k/??
        clock spd     2.8     15  13.75   12.5       16     15     14
                  ======= ====== ====== ======   ====== ====== ======
        Sieve      410.00  99.00 108.00 117.00    98.00  99.00 110.00
        String    1151.20 270.00 292.00 303.67   259.00 262.00 282.00
        Float 1    472.00  92.33  87.00 111.33   123.00 128.00 135.00
        Float 2   1535.00 317.00 394.00 381.67   395.00 415.00 432.00
        Fibinacci 2006.00 605.00 634.00 645.33   507.00 523.00 548.00
        Integer   1553.40 307.00 330.00 346.67   420.00 431.00 443.00

        Dhrystone     236   1136   1063   1000       NA     NA     NA
                *           1351          1183     1282     NA     NA

        * Dhrystone v1.1 re-compiled under ORCA/C v2.0.1

If you look at the numbers, a 12 MHz or faster TWGS/Zip will make everything just about 4x faster than a stock //gs.

System Software 5.0 QuickDraw II improvement test:

Stock //gs: 5648 ticks TWGS 15 MHz: 1332 ticks (over 4x faster than stock)

Is it reliable?

I will need to collect more data for this. Over all, most people have been successful and they are running they TWGS/Zip at 12+ MHz with no problems. I vaguely remember one or two people have problems with the upgrade.

Updates / Changes

Last updated:

09-20-2007 Removed outdated vendor and RAM pricing information (1994!!) and added information regarding the 'Sanyo' '816, also changed power supply and GAL availability information.

08-15-96 Western Design Center sent me their new email address and Home Page Location. Updated.

02-23-95 It's been almost 6 months since the last release. A new Digi-Key catalog came today, plus I was cleaning my file system; both led me to get what ever else needed to update done.

Not much news lately, and I think this FAQ will remain like this for a while...

12-27-94 - I've been lagging greatly on the update. Today I quickly looked though the FAQ and quickly updated what ever was missing... This is a quick release.

11-16-94 - Added some comments about new WDC 14 MHz parts. (not released)

08-22-94 - Major update, availability of true 14 MHz parts!! - New feature for table of content, hope you like it!

08-02-94 - Updated reliability. (~~15)

07-26-94 - Toshi Morita ( added some comments Zip GS. (~~7 ~~8)

07-08-94 - Updated/checked prices on osciallators and SRAM, and some minor changes which hopefully made it easier to read.

06-24-94 - AE is dead now, so GALs are probably not available anymore. Parts like 32 KB cache should still be obtainable from resellers.

03-14-94 - Replaced all mHz with MHz.

01-22-94 - Included which 74HC00 to get for the zip. (~~13)

12-22-93 - Minor appearence update, and some new test results.

12-11-93 - Finally cleaned it up!

12-09-93 - Update the crystal oscillators, SRAM, & RAM prices.

??-??-93 - First version...

There are a lot more questions with answers not included directly in this FAQ; please see for more of them.

Copyright 1998-2007 by Tony Diaz