Replace A1200 CPU on motherboard

[Mrs Beanbag]

this might be a really stupid question, but is it possible to swap the 68EC020 on the A1200 motherboard for a 68030, for instance? And if so, could it be made to run at 28MHz?

I notice there is a blank space there ready for an FPU, could a 68030 go there, while the 68020 is removed? Would that work?

[roy bates]

you mean put an 68882(not a 68030) in the fpu socket and remove the cpu(EC020)?


then how would it boot? you do realise this dont you?

i think you already know the answer.

[amiman99]

http://eab.abime.net/showthread.php?t=33243

[Mrs Beanbag]

Originally Posted by roy bates

you mean put an 68882(not a 68030) in the fpu socket and remove the cpu(EC020)?

No I mean a 68030. I don't know what the pinout of an FPU is but on closer inspection it's a completely different number of pins so that can't work.

I'm just thinking of the A600 accelerators that piggyback directly on the CPU and wondered if something similar were possible on an A1200 using whatever available signals are there on both sockets. But by putting the components directly onto the motherboard.

[roy bates]

Originally Posted by Mrs Beanbag

No I mean a 68030. I don't know what the pinout of an FPU is but on closer inspection it's a completely different number of pins so that can't work.

I'm just thinking of the A600 accelerators that piggyback directly on the CPU and wondered if something similar were possible on an A1200 using whatever available signals are there on both sockets. But by putting the components directly onto the motherboard.

no,an 030 wont work in the fpu space because its not an fpu its integer(apart from the obvios reason you already realised).and it wont work in an 020 space either thats what i was trying to get at.


yes there are accelorators for the 1200 that plug into the trapdoor,no im not being funny.

[Mrs Beanbag]

I know there are accelerators that plug into the trapdoor. I've got one. But it's only an FPU on the inside, it's all just binary on the outside. All those pads on the FPU space must connect to the CPU bus in some way.

Forget it. I should probably go to bed.

[amiman99]

I understand your question, you want to change the 68020 to 68030 and add 68882 fpu to the future fpu spot left on the motherboard.
Looks like changing the CPU will not work, the pin outs are different, but maybe just change it to a full 68020.
There is a spot for FPU on MB and is present in the A1200 schematics, so it looks like it could be possible to install one, I wonder if anyone tried it.
See pic for the pinouts.

[roy bates]

theres no point to a faster cpu without fastram...

you cant change the timings of the motherboard the custum chips wont work...

but you may be able to change the timing of the cpu if you replace it with a faster one.and feed it the required timing.

[Mrs Beanbag]

I don't want to add a 68882, I wondered if the space left for it would be useful for connecting anything else, given that it must connect to the CPU bus in some way. Looks like it connects to most things but only the first few bits of the address bus, which is interesting.

Strange that the '020 and '030 pinouts should be so different, even in the same package. I wonder why they did that. Although the EC020 on the A1200 is rectangular so it must be different again.

The crystal on the board seems to be 28MHz so presumably the signal is halved somewhere. So we should be able to get the full 28MHz from somewhere on the board. Doubt it's as simple as just rerouting the CPU clock line though.

[roy bates]

Originally Posted by Mrs Beanbag

I don't want to add a 68882, I wondered if the space left for it would be useful for connecting anything else, given that it must connect to the CPU bus in some way. Looks like it connects to most things but only the first few bits of the address bus, which is interesting.

Strange that the '020 and '030 pinouts should be so different, even in the same package. I wonder why they did that. Although the EC020 on the A1200 is rectangular so it must be different again.

The crystal on the board seems to be 28MHz so presumably the signal is halved somewhere. So we should be able to get the full 28MHz from somewhere on the board. Doubt it's as simple as just rerouting the CPU clock line though.

why would you doubt you could just send a 28mhz cpu 28mhz from the main clock?

the fpu place on the board is for a fpu only,why is this so hard to understand?
seeing there is a spot for an 020.

[Mrs Beanbag]

Originally Posted by roy bates

why would you doubt you could just send a 28mhz cpu 28mhz from the main clock?

Because the rest of the hardware still has to run at 14MHz and they have to communicate with each other. There will need to be some kind of "glue logic".

the fpu place on the board is for a fpu only,why is this so hard to understand?
seeing there is a spot for an 020.

It is easy to understand, but not necessarily true. Of course it was designed FOR an FPU, but that doesn't mean it can't be used for anything else. It has access to the CPU data bus and various other signals.

[pandy71]

Originally Posted by Mrs Beanbag

Strange that the '020 and '030 pinouts should be so different, even in the same package. I wonder why they did that. Although the EC020 on the A1200 is rectangular so it must be different again.

Why strange - 68030 is different than 68020 and AFAIK there is no 68EC030 that can be comparable to 68EC020 (for example reduced address space to 24 bits).

Originally Posted by Mrs Beanbag

The crystal on the board seems to be 28MHz so presumably the signal is halved somewhere. So we should be able to get the full 28MHz from somewhere on the board. Doubt it's as simple as just rerouting the CPU clock line though.

This should be possible - 68EC020 mounted on A1200 should be able to perform nice with 28MHz clock or even higher.

Perhaps you can use one of those modern clock multipliers generators
http://www.onsemi.com/PowerSolutions....do?id=NB3N501
http://www.onsemi.com/PowerSolutions....do?id=NB3N502
http://www.onsemi.com/PowerSolutions....do?id=NB3N511

or a bit more complex

http://www.onsemi.com/PowerSolutions...t.do?id=FS6370

[Mrs Beanbag]

Originally Posted by pandy71

Why strange - 68030 is different than 68020

true, but even the signals that they both share are in completely different places.

This should be possible - 68EC020 mounted on A1200 should be able to perform nice with 28MHz clock or even higher.

Perhaps you can use one of those modern clock multipliers generators

But there is already a 28MHz signal on the board somewhere, can we not just bypass the clock divider?

There is, unfortunately, only a 25MHz version of the 68EC020, as far as I can find, but maybe it will overclock a bit. Perhaps with a little heatsink.

[Amiga1992]

A 28Mhz hack would be really interesting!

[roy bates]

i didnt say anything about changing any other timing on the board did i?
if you have a look back at a previus post you will see why i wouldnt say that.

if you look at any amiga motherboard there is a 28mhz clock sitting on the motherboard,it isent somewhere its in plain view.


theres a pin on the cpu that says CLK,you know what its for.

why do you think the motherboard was disigned to have a fpu there,and not say...an intiger unit?

BTW,the clock doesent just get halfed to 14mhz for the cpu.
anyway who says you have to run it at 28mhz? you can give its own clock signal.



actually im wondering,are you going to try to do this?

[pandy71]

Originally Posted by Mrs Beanbag

true, but even the signals that they both share are in completely different places.

QFP is not good for this - ZIF sockets are very rare and very expenssive.

Originally Posted by Mrs Beanbag

But there is already a 28MHz signal on the board somewhere, can we not just bypass the clock divider?

Not sure about phase relations - this can be important.

Originally Posted by Mrs Beanbag

There is, unfortunately, only a 25MHz version of the 68EC020, as far as I can find, but maybe it will overclock a bit. Perhaps with a little heatsink.

Heatsink for sure is recomended, Motorola was quite famous for offering higher CLK versions with lower marking - overclock should be easy.

[8bitbubsy]

Wouldn't this also speed up chip RAM access? So you'd maybe need faster chip RAM or to add (more?) waitstates...
And what about the PCMCIA port?
EDIT: Nevermind.. I guess chip RAM is clocked with the custom chip clock... Makes sense that there's chip RAM and fast RAM.

[roy bates]

Originally Posted by 8bitbubsy

Wouldn't this also speed up chip RAM access? So you'd maybe need faster chip RAM or to add (more?) waitstates...
And what about the PCMCIA port?
EDIT: Nevermind.. I guess chip RAM is clocked with the custom chip clock... Makes sense that there's chip RAM and fast RAM.

exactly

[Mrs Beanbag]

Originally Posted by roy bates

i didnt say anything about changing any other timing on the board did i?
if you have a look back at a previus post you will see why i wouldnt say that.

if you look at any amiga motherboard there is a 28mhz clock sitting on the motherboard,it isent somewhere its in plain view.

Yes the reason I said it is because I saw it. You seem to be getting quite upset about this.

theres a pin on the cpu that says CLK,you know what its for. ... BTW,the clock doesent just get halfed to 14mhz for the cpu.

Yes I know what it is for but you can't just clock a CPU at a different speed than the hardware it's connected to without some sort of buffer in between them. Running the CPU at 28MHz, it would be trying to access the chipset, chip RAM etc, at 28MHz as well, which won't work. They designed the Amiga around a single clock signal on purpose, because it made things simpler. It's not like a modern PC which is designed for the CPU to be able to run at arbitrary frequency.

why do you think the motherboard was disigned to have a fpu there,and not say...an intiger unit?

It really doesn't matter why it was designed that way now, does it? They are just signals, you can do what you like with them. Electronics is not magic. I'm thinking outside of the box here.

actually im wondering,are you going to try to do this?

ah. well that would be telling.

[roy bates]

that means you dont know,considering your the one asking questions about adding a 68030 to a place made for a 68882 and wont accept it wont work

have a look at some other amigas apart from 600's and 1200's and say there cpu's are clocked at custom chipset speeds via dividers based on the main clock,and then tell everyone they cant run at a different speed to them.

<snip - prowler>