Just a small update here, this project isn't dead and I am still working hard into booster stuff. I just do not update the forum with step by step progress anymore and it takes up to much time.
The old page is here which covers work up until the end of last year. http://www.exxoshost.co.uk/atari/last/16mhz/index.htm
This years work is covered on page 2http://www.exxoshost.co.uk/atari/last/16mhz/index2.htm
Basically the round up is I have the CPU running ASYNC finally and had it running at 25MHz. I couldn't go any higher (didn't have anymore osc's to hand) but the CPU E-clock running faster causes the ACIA to screw up. After a lot of work, I gave up and decided to do a new test board using the 68SEC000.
This CPU needs a little more "work" as some signals are missing, but the good news is that its almost wired up the same as the 020 CPU. This makes it a little easier to adapt the CPU as there is actually working code examples and also it is possible it wouldn't be much more work to move to the 020.
Now people people get twitchy, The 68SEC000 is still a 68000 core, its just more like a EC version, so some pins are missing, but the same pins are missing on the 020 and get emulated.
According to what I read on the Amiga threads, they claim 50-100MHz is possible with the SEC CPU. If that is true or not, not idea. Though I think the SEC is likely a later production run over the 68HC000 so it should overclock better. We shall see.
I need to look at ROM's again as I am using 55ns ROMs which are about as fast as I could find in 5V, but that struggles to keep up with 32MHz speeds. So if I can find a faster ROM, then higher ROM speeds can be done, otherwise , regardless of CPU speed, the effective ROM speed might be maxed out at about 40MHz. I'd rather not get into adding waitsates for stuff, but this depends on what parts are obtainable. I think someone did suggest some microchip ROM's last year, but can't remember who or what.
SRAM is also hard to find in 5V types. I think I used some 2MB devices and used 5 of them on my board for 10MB. Those were 45ns so again its going to start maxing out somewhere around 40MHz.
Likely I will look into 3.3V buffer chips again, I did look last year and did half plan what I wanted to use. I think 3.3V world may give me a few more options with ROM and SRAM.. though work for another day..
I have designed a fast-ram board which will work at 32MHz easily. Though with me working on the CPU issues, the fast-ram will have to wait. Also similar with the IDE, I've designed a new IDE circuit myself which conforms to proper IDE timing spec, so all those odd stability/write issues with various interfaces should hopefully be no more. Again while I have designed it and simulated it, no time to build and test it yet.
I am also aware people want various features, like flash ROM and the ability to switch the booster on/off in software. What I am thinking is having TOS206 as default (or first block) and then a user programmed block which can be written with EMUTOS or whatever.
If EMUTOS builds don't use the full flash area (assume there will be a few bytes free at the end of the ROM free) then I will likely use that as a booster register to store settings, such as the boot rom block choice and booster on/off etc.
Please don't ask me "when will this be valuable" as I produce so many kits now my time working on the booster stuff is getting down to just a few days a year currently. I have people waiting for 3+ months for the Falcon PSU's and I have a few Falcons coming in for repair soon as well. So I likely won't have time to work on boosters for 2 or 3 months. Progress is posted as it happens on my site, currently I am working on the new 68SEC000 PCB layout which is almost finished.
Though if anyone wants to save me some work, have a look into ROM and SRAM, see what's available speed and size wise, of course they need to be low cost. 45ns or better, and 16bit. Ideally 5V, but 3.3V could be a option. The best IC is something 16bit with 4MB or more RAM, less IC's is less soldering, less PCB routing and keeps costs down etc. With space in the ST's case being so limited, getting it all to fit is a huge battle. So less IC's means more chance of it being possible to fit in the original case.