Applied Engineering produced many advanced and unusual add-on devices for the Apple II product line. One of these was a 65C816 CPU card for the Apple IIe, which replaced the processor with a daughter card.

Hardware manual for the board: https://archive.org/details/AE_65816_16bit_Card_Software_Developers_Guide

Were there any practical applications for this, or was it primarily just a novelty/toy for aspiring hardware engineers to play with?

Although the IIgs was based on the 65C816, programs from a IIgs would not necessarily run on this, since the AE board did not have the same ROM / toolbox routines, enhanced video, or other hardware.

  • Pedantic: is it a coprocessor if it replaces the original processor? The linked developers' guide covers topics like soft switches still working as they ever did so I think it's a plain processor upgrade. I'll let somebody who actually knows something comment on any practical applications that may have been forthcoming, though I guess whether it effectively became a novelty/toy is distinct from whether it was intended as one?
    – Tommy
    Mar 27, 2018 at 14:52

3 Answers 3


Simple answer: More RAM.

Instead of flipping around Language Card and Aux Memory banks, the 65816 allowed (native) programs to address up to 16 MiB in an (almost) flat way. Programs no longer had to keep track with complicated addressing schemes about their data and (if larger than ~48 KiB) their program modules.

As a side effect, using 16 Bit instructions could speed up the code a bit. While this isn't the same as having a way faster IIgs, it still adds - and simplifies programming again.

Were there any practical applications for this, or was it primarily just a novelty/toy for aspiring hardware engineers to play with?

The only real target where developer owning a maxed out IIe with some AE RAM Card. By buying the AE 65816 card they could go ahead and develop IIgs software while postponing the investment in a IIgs, which might have included the need for new drives and so on. It was a cheap intermediate solution for a few.

Inserting a 65802 was another common way to enable 65816 code for the Apple II. Even cheaper, but with a 65802 programs were still confined to the original 64Ki address space of the II, thus using the most important difference, large memory in 'flat' addressing was impossible.

  • Idiot's follow-up query: was there much in the way of third-party support? E.g. would there every have been any advantage to purchase for a business user?
    – Tommy
    Mar 27, 2018 at 15:04
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    Modified the answer to include tpossible usage, as that was also part of the original question.
    – Raffzahn
    Mar 27, 2018 at 15:57
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    The Merlin 16 assembler required a IIgs or 128k IIe//IIc with a 65802. Mar 27, 2018 at 20:48
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    @Raffzahn Please correct all the typos ... ;) Mar 28, 2018 at 18:07
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    I jumped in and fixed the typos; I wouldn't normally touch somebody else's answer for mere typography but it sounded like @Raffzahn didn't think it would be offensive and I happened to be passing. I hate treading on toes, I hope that's okay.
    – Tommy
    Mar 28, 2018 at 18:49

Simple answer: Performance, and not more RAM. ; - )

Although some 16-bit options expanded RAM, the AE 65C816 16 Bit Card (which was not released commercially) connected to an optional RAM card, one already used by existing applications.

The main practical application would (eventually) have been running a more powerful development environment - e.g. Merlin 16 - to write software for the 8-bit Apple II series.

I used Merlin 16+ on a IIgs for this purpose, but booting up GS/OS just to start Merlin was a pain. If you want to write IIgs software, you need a IIgs. But this card would've been fine for 8-bit software.

Even before the IIgs was released there were a number of options to upgrade existing Apple II computers with the 16-bit chips (65802 or 65816), in which case the only common ground would have been the 16-bit instructions - not more RAM - because only the products supporting the 24-bit addressing would provide that. It's obvious in retrospect that these fragmented products would remain a niche for development tools and tinkering, and that the IIgs would soon eclipse them.

For example the August 1986 issue of Open-Apple lists these 16-bit options, two with RAM:

1. 65802 chip. No RAM benefits. $50.
2. Com Log Apple16 65816 Co-Processor Board. Onboard 256K RAM. $395.
3. Checkmate Technology MultiRAM EX 65816 Co-Processor Card. Optional RAM card. $189.
4. Applied Engineering 65C816 16 Bit Card. Optional RAM card. $159. (Not released.)
5. Checkmate Technology 65C816 upgrade for CX Board for //c. Requires CX Board. $119.95.
6. Applied Engineering Transwarp Card l6 bit option (65802). Requires Transwarp Card. $89.

Open-Apple also states that only three 16-bit capable assemblers were available at that time:

1. Merlin Pro
2. Orca/M
3. S.C Macro Assembler

These were all 8-bit applications that could assemble 16-bit code, but Merlin 16 (which required a 16-bit CPU) was already in beta when the above was published, so there was already a market for 16-bit //e or //c software. When it was released there is evidence that development productivity benefited from the 16-bit chips, and Roger Wagner Publishing marketed 16-bit upgrade options without extra RAM to developers.

Apple IIe and IIc users can take advantage of [twice as fast] Merlin 16 assemblies, a more powerful Full Screen Editor and a newer, [five times faster] and more versatile Linker just by swapping their existing 6502 or 65C02 microprocessor with a replacement 65802 chip, available also from Roger Wagner Publishing, Inc.

And ...

By special arrangement with Applied Engineering, Inc., Roger Wagner Publishing is offering the powerful and popular Transwarp Accelerator Card for the Apple IIe with a 65802 microprocessor already installed. Using this card, Apple IIe owners can run Merlin 16 and assemble programs faster than the Ilgs, in fact, four times faster than a standard IIe running Merlin 8

  • Nice line up. Thanks. Only the speed gain by switching to a 65802 was rather meager. You're quotes even contradct themself. If a Merlin 16 on a 65802 Transwarp with 3.6 MHz runs almost 4 times faster than a Merlin 8 on a standard IIe, then it can't run twice as fast on the same IIe by just swaping the CPU. Isn't it? I'd say quite some wishful tinking.
    – Raffzahn
    Mar 29, 2018 at 11:52
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    @Raffzahn Good point about the speed quotes, thanks. That's marketing for you. ; - ) But recently I've been porting an 8-bit demo to the IIgs and I was surprised at the improvement when I wrote a mostly 8-bit SHR plot routine (70 bytes) and then converted it to 16-bit (46 bytes). I'll update this answer when I can do some performance comparisons - though I don't have a Transwarp. Mar 29, 2018 at 22:53
  • Well, Nick, ofc, there are substantial speed gains in certain areas. It depends much on the applications compared. On plain 6502 code Transwarp is much like a IIgs. Otehrwise it again depends on the application. - I did much development on the II back then (prefering the Orca/M environment), and I'm well aware about the gains. My point is that the gains are rather meager in general. Cranking up the CPU had a way bigger impact.
    – Raffzahn
    Mar 29, 2018 at 23:03
  • The first claim is not realy related to any speed gain due the new processor, as it compares two different programs (Merlin 16 vs. Merlin 8). Any of the claimed speed gain is more likely due new algorithms than any CPU speed up. It's more like comparing Apples and oranges.
    – Raffzahn
    Mar 29, 2018 at 23:45
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    Merlin 8 and 16 are not that different - they still perform the same functions. In fact skimming the source code Merlin 16 (e.g. the linker) still has the structure, labels and comments of Merlin 8, so it's a 16-bit port with more functionality. It makes sense that linking benefits more in 16 bits because there's a lot of word-based math (like my SHR plot routine) whereas assembling is byte-oriented parsing. There were no revolutionary linking algorithms AFAIK. ; - ) Mar 30, 2018 at 9:51

I seem to recall there was some graphic spreadsheet program that would take advantage of an AE 65816 16 bit card if one was installed. It was advertised in Apple II magazines back in the day (VIP Professional by Applied Engineering). I personally have a Laser 128EX with a 65802 installed. I had to write my own software to take advantage of its native mode capabilities which resulted in faster, denser code. I was impressed with the smooth and fast scrolling in an editor I used for programming. The disadvantage was that in order to use any firmware, emulation mode had to be switched in. Firmware in this sense means the 6502 ROM routines for input, output etc that the computer originally came installed. IRQs could be used in native mode if upper ram was switched in and native mode handler was called. Fun times...

Cheers! Andy

  • Could you clarify the sentence "The disadvantage was that in order to use any firmware emulation mode had to be switched in."? Currently I don't know whether it's "firmware", "firmware emulation" or "firmware emulation mode" that you want to use, and I don't know what's being switched in.
    – wizzwizz4
    Mar 30, 2018 at 16:45

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