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If you're interested, I'd grab Quartus II 13.0sp1 before Intel takes it down (they're real jerks about keeping downloads available), that's the last version that supports the MAX7000 series with which the Atmel 150x chips are compatible.

Well, I spent an interesting morning teaching myself Verilog and translating my CUPL design into it, and... success! The clock generator side of the IWM appears to be working perfectly. There's more to do, of course, but this is a big step and definitely proves out the workflow of using...

I think you understand more or less correctly, yes, though the IWM's WRDATA output actually toggles to represent ones, as differentiated from the RDDATA input, which interprets falling edges as ones. I'd be lying if I said I understood exactly why this is or what it translates to on the disk...

The input clocks are 2 MHz on Q3 and either 7 MHz or 8 MHz on FCLK (I don't believe FCLK existed in the Disk II, or at least, it wasn't used for bit cell timing). Q3 is only used in the synchronous mode for bit cell timing and eight periods of it in slow mode (4 µs) or four periods in fast mode...

The more I think about this, I am starting to wonder, maybe it would make more sense to target one 1508. I'm thinking that thanks to a fatal bug in the Atmel fitter, I might have to start over and implement this in Verilog instead of CUPL (which is going to be interesting as I don't actually...

No great reason, but two 1504s are actually cheaper than one 1508.

Hmm. Is it possible to throw newly-available SRAM of some kind in there, or does it have to be DRAM?

Oh, that raises an interesting question - are the necessary DRAM ICs available new, or do they have to be recovered from elsewhere?

Yeah, I don't think Woz has much control over what Apple releases, that'll be squarely in the court of the legal department, and sadly, it's much easier to say no than it is to potentially open yourself up to some form of legal liability. At least they've allowed the release of the IWM spec...

Well, ish. =D It is backward compatible with the Disk II, but some features are entirely new. Some of these are relatively trivial (slow/fast mode just halves/doubles the clock, for example), but the asynchronous mode that the Mac uses is a bit more complex...

So I've been playing around with this for a bit and I've started wondering, why make a minimal, corner-cutting clone of the IWM when I can make a full-fledged clone of the IWM? And I think I might be able to, all in logic. The target platform is a pair of ATF1504s, one as the clock generator...

Like the !ENBL1 and !ENBL2 lines? I know the IWM has no head select mechanism but I've never heard there was anything awry with the drive select lines...

I've spent a bunch of time trying to nail down the logic side of this, and after several false starts, I think I have a working strategy. I hope one day to use a Renesas GreenPak or two in one of my designs, but it won't be this time, sadly - I'll be using an Atmel ATF1504 CPLD for the CPU...

Thanks for the suggestion, and I know it comes from a good place, so please don't take what follows as an attack, it is not meant that way. (Also, please forgive the string of ham-fisted metaphors.) I die a little inside every time someone tells me to use an RP2040 or STM32 or whatever the...

Ladies and gentlemen, my next trick is impossible improbable... It seems like the IWM is the only (or at least the biggest) thing standing in the way of a Plus or SE made of entirely new parts - and possibly also the biggest problem for those trying to revive an old board. For completeness's...

Gah, sorry for the late reply, this fell between the proverbial cracks... _______________ _____________ | \o o o o o/ | | | _____ | | |___\o_o_o_o/___| |_|_________|_| ||||||||| ||||||||| ||||||||| ||||||||| ||||||||| ||||||||| |||||||||...

Uploading the hex file with ghofbauer's change for an external oscillator here, in case anyone else finds it useful.

Sure, I can do that, though if it is the clock that's still at fault, I'd really like to be able to cook up a solution that just slots in without any external hacks like this...

This is great stuff! I love how many subprojects contributed to make it possible and I'm happy to have played a small part in realizing it. What's left besides the IWM to make a Plus that's totally free of parts that have to be recovered from vintage machines?

Hmm. Well, it's a data point, at least. I assume it's the same PIC16F87/88 you're testing in both boards and it works in one but not the other? Also, I've forgotten - do you have a TechStep? If so, can you check on the working SE whether the PIC16F87/88 passes the ADB test? Other than that...