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| Classic II FPU card design |
Posted by: maceffects on 2021-01-28 11:49:44
Maybe someone can correct me but I thought the the speed should match the speed of the processor? Shouldn’t they be 16mhz/16mhz?
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Posted by: LarBob on 2021-01-28 12:02:11
Maybe someone can correct me but I thought the the speed should match the speed of the processor? Shouldn’t they be 16mhz/16mhz? Nope, see the datasheet for the MC68882 (specifically page 5-98/PDF page 3). The CPU and the MC68882 work fine together at different clock speeds.
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Posted by: maceffects on 2021-01-28 12:33:11
Nope, see the datasheet for the MC68882 (specifically page 5-98/PDF page 3). The CPU and the MC68882 work fine together at different clock speeds. Thanks, I remember some processors used to be really fussy about that. I’m glad this allows for flexibility.
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Posted by: moldy on 2021-01-28 19:59:03
Thanks, I remember some processors used to be really fussy about that. I’m glad this allows for flexibility. If you look at my screenshot from MacBench, you can see the results for two frequencies (@16M and @40M; the CPU was always at the default 16M). 40M gives a slight boost to the benchmark score. The card itself has a jumper to configure which clock to use (OSC means the oscillator on the card, SYS is using the C16M signal from the logic board which is 16M).
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Posted by: LaPorta on 2021-01-29 02:14:13
Thanks everyone. So I'd definitely buy one, and hopefully Kai can give us a link to the NOS 40s...I'd be all in!
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Posted by: mattsoft on 2021-01-29 03:36:59
I don't have a Classic II, but projects like this are just awesome. Nice work moldy!
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Posted by: Kai Robinson on 2021-01-29 09:22:32
Thanks everyone. So I'd definitely buy one, and hopefully Kai can give us a link to the NOS 40s...I'd be all in! Well, you can buy individually, or i can order a load en-masse, and distribute?
https://www.utsource.net/itm/p/1862306.html
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Posted by: LaPorta on 2021-01-29 09:46:26
Man, is that shipping ever steep! Guess it would work out if as you said we distributed, but not from the UK I sould suppose.
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Posted by: Paralel on 2022-01-04 19:49:16
I am currently working on a derivative of this design that would support the 50 MHz part 68882. It's a PGA, which is the only major difference between it and the rest of the 68882 series. The only reason is "because". Sort of like most of the projects for 68k Macs. |
Posted by: moldy on 2022-01-05 02:33:31
I am currently working on a derivative of this design that would support the 50 MHz part 68882. Super cool, glad to see someone picked up on this, let us know how it goes! 🙂 |
Posted by: Tashtari on 2022-03-29 16:24:15
Any good place to get one of these assembled? A Classic II recently came into my possession and I'm interested in giving it toys, but my soldering skills are pitiable. |
Posted by: moldy on 2022-03-31 14:35:28
Any good place to get one of these assembled? A Classic II recently came into my possession and I'm interested in giving it toys, but my soldering skills are pitiable. I realized I still have two units of my original batch that I planned to sell (but the thread disappeared in the forum crash) - if you're interested just shoot me a PM!
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Posted by: aplmak on 2022-11-18 19:21:21
Where can you find a mc68882fn40a that’s not fake these days?? Aren’t most of them fake Chinese made ones?? |
Posted by: moldy on 2022-11-21 07:42:25
Where can you find a mc68882fn40a that’s not fake these days?? Aren’t most of them fake Chinese made ones?? I sourced some genuine one from local auction sites with NOS chips. Alternatively the ones from China (Ali/eBay) even though potentially remarked, work pretty reliably and cool for me 🙂 |
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