exxos's Atari, Amiga & retro forum

Forgottenmyname wrote: 04 Feb 2019 11:57 Well done Exxos

:thanksyellow:

I need to find a 55MHz osc somehow now :lol:

Hopefully this now (finally!) marks the end of my 68000 booster research :)

Got a 233mhz one if you wanna try it :D

A while ago I was working on the fast RAM version...

https://www.exxosforum.co.uk/forum/viewt ... q-Y#p14194

Which was actually a huge waste of time, as I now had to do a lot of design changes the current SEC booster :roll:

So I have added back on the fast ram onto the modified board, along with flash.

I did have ROM on the previous board, but as flash is on the board, and can be used externally with ROM anyway, there is little use in adding it to this board. It will also make fitting the board in the STFM actually fit without in the way of the MMU.

So this will keep me busy for a while..

You know, you could skip 55Mhz and go straight for 60......

rubber_jonnie wrote: 04 Feb 2019 14:09 You know, you could skip 55Mhz and go straight for 60......

From tests before it maxed out at 58MHz. There doesn't seem to be any oscs around in that range though :( Next jump seems to be 64.

exxos wrote: 04 Feb 2019 14:12

rubber_jonnie wrote: 04 Feb 2019 14:09 You know, you could skip 55Mhz and go straight for 60......

From tests before it maxed out at 58MHz. There doesn't seem to be any oscs around in that range though :( Next jump seems to be 64.

64 it is then ;)

I guess there will be a logical point at which the CPUs can't be overclocked anymore. Would be very cool if it could be switched in software.

rubber_jonnie wrote: 04 Feb 2019 14:19 64 it is then ;)

If I can find the OSC I will try it again, but doubt it will work.

rubber_jonnie wrote: 04 Feb 2019 14:19 Would be very cool if it could be switched in software.

It is on the "to do list" but I am having issues with realtime clock switching on this board. So even switching speeds with the power on isn't going to be possible for a while. I will investigate it eventually, but I want to get on with something else like the fast-ram and flash-rom.

exxos wrote: 04 Feb 2019 14:29
It is on the "to do list" but I am having issues with realtime clock switching on this board. So even switching speeds with the power on isn't going to be possible for a while. I will investigate it eventually, but I want to get on with something else like the fast-ram and flash-rom.

I can understand, makes sense to get the other stuff in place, that will make a big difference.

rubber_jonnie wrote: 04 Feb 2019 14:48 I can understand, makes sense to get the other stuff in place, that will make a big difference.

I tried 64MHz.. Basically nope.. bombs on 104, 206 doesn't even try. I added in some more delays, but nope...

If I remember rightly, during my last tests, what I did was to literally just run the CPU faster on integer division test. I think it would basically lock up halfway through the test each time.

It may not necessarily be the CPU cannot run that fast, but the bus itself probably isn't anywhere near stable enough for it. Of course I already hit issues with 50MHz :(

Even so, even 50MHz is probably way too fast. Look at it that how fast they cycle is now, basically 20ns.

Even adding fast ram would mean we would need 10ns RAM which is hard to find and incredibly expensive.

I think talked about this previously that I was considering using a small bank of fast ram (10ns) to copy the ROM contents to during start-up. This is because the flash and ROM chips are basically too slow by themselves. So even adding flash is going to slow ROM access down.

In terms of fast ram, I think we will be pushed to even get 60ns RAM access speed. Which basically equates to 32MHz speeds. Realistically 32MHz would be a much better point to operate at.

It would make sense that the bus and maybe other components may not be happy when pushing way beyond the original 8Mhz speed.

I have to take my hat off to you that you've got so far with this.

:bravo: