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DIY Atari STE CPU Adapter

DIY Atari STE CPU Adapter

Postby Awol » Sun Mar 07, 2010 7:08 am

I bought a brand new boxed "ICD Adspeed 16" 16 MHz accelerator on eBay last summer for $30 shipped. It's supposed to replace the CPU in an STF. I could put it in my stock STF, but I'd rather put it in my STE (which I've already upgraded to 4MB RAM and TOS 2.06). STF's and STE's use the same CPU - the only problem is that the STF's CPU comes in a rectangular 64-pin DIP form, while the STE's CPU comes in a square 68-pin PLCC form. So a while ago over winter break I made my own CPU adapter:

http://8bitcollective.com/items/images/CPU%20Adapter.JPG

Don't laugh! It's my first ever attempt at circuitboard etching, and I didn't have the patience to figure out a circuit design program, so I hand drew the circuits with Sharpie and nail polish. I'm not the neatest at soldering either. :)

Here it is installed in my STE, with the STF accelerator in the socket:

http://8bitcollective.com/items/images/CPU%20Adapter%20Inside.JPG

There's not a lot of room in the computer so I made 2 boards and connected them with wire. It didn't occur to me to use ribbon cable until afterwards. So that's what it looks like... a little sketchy, but the important thing is that it should theoretically work (corresponding pins properly connected, no short circuits). The problem is that in practice it doesn't work for some reason. I've unplugged and replugged it a few times, but every time I turn on the STE I get either a blank white screen or 20 bombs. I used my multimeter's continuity test to make sure each pair of pins is connected properly, and to make sure there are no short circuits between wrong pins. I'm sure each pin is connected to the correct corresponding pin too. I don't know what's wrong. Anyone have any suggestions? Someone told me it might be that the CPU signals are too weak to travel through the long wires. The chronicles of this project are in a thread on Atari-Forum here.

I've declared the project a failure for now, but I thought you guys might like to see it anyway. I did learn a lot from the attempt though. Maybe I'll give it another shot in the summer. If all else fails I can just stick the accelerator in my STF or sell it. Or perhaps trade with someone who's got an STE accelerator? ;)
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Re: DIY Atari STE CPU Adapter

Postby NCGM » Sun Mar 07, 2010 2:19 pm

I've managed to find a 16MHz 68-pin PLCC CPU and I intend to use it as an upgrade in my main STE (I have three). Now my soldering skills are at the beginner stage but even so, I read Simbo's ideas in a thread at the Atari-Forum where he described soldering a few wires here and there. I like this idea for the reason that my existing IDE interface can remain piggy backed on top of the main CPU. Other upgrade boards tend to hog the whole CPU socket with no room for further expansion.


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Re: DIY Atari STE CPU Adapter

Postby Awol » Mon Mar 08, 2010 4:10 am

NCGM wrote:I've managed to find a 16MHz 68-pin PLCC CPU and I intend to use it as an upgrade in my main STE (I have three).

Cool! I don't think you can just swap it with the normal CPU though. The accelerator has some extra circuitry besides the 16 MHz CPU.

NCGM wrote:Now my soldering skills are at the beginner stage but even so, I read Simbo's ideas in a thread at the Atari-Forum where he described soldering a few wires here and there.

Link please? And let me know if you get it to work! If so, I might have to find one of those 16 MHz CPU's and try it too!

NCGM wrote:I like this idea for the reason that my existing IDE interface can remain piggy backed on top of the main CPU. Other upgrade boards tend to hog the whole CPU socket with no room for further expansion.

Yeah, there's not a lot of room inside the computer, which is part of why I split my adapter board into two parts connected by wires. I was trying to figure out a way to fit it all in without cutting holes in anything. The STF accelerator is pretty tall.
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Re: DIY Atari STE CPU Adapter

Postby NCGM » Mon Mar 08, 2010 12:45 pm

Have a read of this page within this thread; read it carefully as Simbo's English is not easy to follow but you will get the basic idea.

http://www.atari-forum.com/viewtopic.php?f=74&t=16761&start=25#p159417


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Re: DIY Atari STE CPU Adapter

Postby Awol » Tue Mar 09, 2010 1:57 am

Thanks! I'll have to keep an eye out for a 16 MHz PLCC CPU. I saw a 16 MHz DIP on eBay a while ago, but didn't bid since I had an actual accelerator.
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Re: DIY Atari STE CPU Adapter

Postby Atari Music Network » Wed Mar 10, 2010 9:40 am

If you get this mod to work the way you want it, would you ever consider developing and manufacture a whole batch to sell? This is an incredibly creative endeavor that I'm sure a lot of enthusiasts would appreciate having (without doing the work, of course!)
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Re: DIY Atari STE CPU Adapter

Postby Awol » Wed Mar 10, 2010 6:51 pm

Atari Music Network wrote:If you get this mod to work the way you want it, would you ever consider developing and manufacture a whole batch to sell? This is an incredibly creative endeavor that I'm sure a lot of enthusiasts would appreciate having (without doing the work, of course!)

No! Sorry, I just don't have the time or patience for that! XD
I'd put up a schematic so people could make their own, but I don't know how to use a circuit design program. It's pretty straightforward though (connect pin A on DIP to pin A on PLCC, connect pin B on DIP to pin B on PLCC, etc). You can find the pinouts for each chip online.
Thanks for your interest though! :D
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Re: DIY Atari STE CPU Adapter

Postby Awol » Sat Mar 13, 2010 1:34 pm

Wow! Didn't even know a 28 MHz STE accelerator existed!
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Re: DIY Atari STE CPU Adapter

Postby Guest » Sat Mar 13, 2010 10:08 pm

There was also a memory expansion board for the STe which allowed up to 12MB RAM (The 68000 can access up to 16MB form it's address bus) and a version was promised for the regular ST line as well. I remember reading the review of the STe boards and seeing them advertised, though never saw anything of the ST one.

Never seen them on ebay though, so I suspect very few were sold (They were stupidly expensive at the time, especially with RAM installed), or those that have them keep them.

Now imagine THAT with a 16MHz or 28MHz STe!
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Re: DIY Atari STE CPU Adapter

Postby Atari Music Network » Sun Mar 14, 2010 6:34 am

It never ceases to amaze me how many rare, mysterious addon devices were made for the Atari computer line. This 28MHz accelerator sold for £129.00!
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Re: DIY Atari STE CPU Adapter

Postby NCGM » Sun Mar 14, 2010 12:34 pm

Yes a similar CPU upgrade sold for a similar price on Ebay last year.
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