April 5th, 2015

Scalable Oscillator for TranswarpGS

We’re big fans of the Apple IIGS (well, duh) but for all its cool graphics and sound capabilities, it’s kinda pokey when running its native GSOS GUI and compatible applications. That’s why accelerators are always in demand. They replace the stock 2.8MHz processor with a faster 65c816 on a card, usually 7MHz or faster, and give the IIGS a much needed kick in the pants. Thankfully, accelerators are about to become more plentiful.

For some people though, 7MHz isn’t good enough. The TranswarpGS accelerator itself can be made better, stronger, faster. We have the technology in the form of improved 65c816 processor, newer cache RAM, active cooling and an overall better understanding of the TranswarpGS board layout and GAL logic. Through upgrades, the TranswarpGS can be reliably overclocked beyond its original specifications.

Now we get to the figurative heart of the matter, the oscillator crystal that determines the speed of the accelerator. Like most accelerators for the Apple IIGS, the speed of a TranswarpGS is derived by dividing the oscillator’s frequency by 4. So a 28MHz oscillator results in a 7MHz operation, 32MHz equals an 8MHz board and so on. But even with upgrades, we can only push our 80’s technology accelerator so far before it balks and begins to malfunction. Not all TranswarpGS boards are equal either. Some boards upgrade more easily and go faster than others. To find out, you’ll need to keep a variety of oscillators on hand. Maybe several.

If only there was a way to easily and conveniently overclock the oscillator’s frequency until the optimal speed for reliable operation could be determined.

Now there is. From UltimateApple2 and ReactiveMicro, we have the new Scalable Oscillator, a small augmented oscillator replacement that works with your TranswarpGS accelerator (and probably ZipGS).

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Scalable Oscillator front and back

The Scalable Oscillator (aka SO) replaces the fixed-frequency oscillator on your TranswarpGS. A series of DIP switches determines what speed the SO runs at, from 28MHz through to a maximum 80MHz in .25MHz increments — that’s 7MHz through 20MHz in system speed.

The DIP switches from top to bottom are labeled 1-8. Switches 1-7 control the oscillator frequency using binary code, while switch 8 enables/disables the SO. You can piggyback your original oscillator into the SO for normal operation (by setting DIP 8 to off) but… we’re here to GO FASTER! AM I RIGHT?

The binary code used for DIPs 1-7 is determined by taking the desired oscillator speed and subtracting 8 from it. For example, to run your SO-enabled TranswarpGS at 10MHz, you need a 40MHz oscillator frequency signal — subtract 8 from 40, you get 32. 32 in binary is 0100000 or off, on, off, off, off, off, off. Simple, right? Don’t worry, a handy chart will be included with all (53!) possible DIP settings for the binary challenged.

A2Central and Mike Maginnis of the Open Apple podcast were allowed a sneak peek to play with this new tweaker toy. We discussed some of our hands-on experiences in OA Episode #45 but I’ll also post some of my perceptions here.

First off, the SO works as advertised. It was relatively painless to set the SO output frequency per the included chart (which you will *not* want to lose). You might be one of those set it and forget it types, but for anyone who likes to tweak their hardware, printing the chart out and taping it to your power supply or the underside of your IIGS lid might be a good idea. That way, its always there when you need it. BTW, this is *that moment* your middle school teacher said you’d need to know binary for someday.

The SO is pretty small. I had to remove it from the TWGS whenever I set the DIPs but that’s because my TWGS also has a fan upgrade installed (another fine option from ReactiveMicro). It could be tricky removing and installing the SO (but not impossible) while under the fan… but with the fan left in place setting the DIPs with a toothpick was equally tricky. That might be attributable to my excessive (i.e. obsessive) care (i.e. paranoia) over electrostatic discharge during the handling of all the components. I’m kind of a klutz.

I have to say, I very much like the Scalable Oscillator. For me, it beats keeping a drawer full of miscellaneous oscillators around.

The anticipated price of the Scalable Oscillator is a reasonable $35 USD and will be available in quantity within a few weeks.

April 4th, 2015

Coming soon from Tecnobytes Classic Computers

Coming Soon

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