Amiga 1200 motherboard FPU upgrade?

[Steve T]

From the embarrassing questions thread, apparently it is possible to add FPU directly to the 1200 mobo - there's an empty space to the left of the 020 on the motherboard specifically for this.

A possible overlooked upgrade option? I realise FPU's are less than essential for much amiga stuff, but I would personally have some use for one.

-Has anyone here done this & does it really work?

-Did Commodore ever produce any 1200's with FPU's built in?

-Would it conflict with, or by design is switched off by a non-FPU equipped trapdoor accelerator?

[dJOS]

Hmm that would be cool, I'd luv to run povray on my aca1220 equipped a1200 with a real FPU!

[NovaCoder]

This has come up a few times now, I don't think it will work.

Even if it did work it would be next to useless as a 14Mhz FPU cannot really do much.

They'd have been better off designing the MB without either CPU/FPU and selling them with an accelerator instead, that way people could have chosen their system specs when they brought the computer (And we wouldn't have a unused CPU sitting on our MB's).

[delshay]

The FPU on motherboard does work,I have it install as standard on my test motherboard. But I have never complete what I wanted to do with this along with 25Mhz 68EC020 which is also on motherboard of all my A1200(s) along with 60ns chip ram chips,not sure where I am going with this but is on my to do list.

FPU may can be clocked separately did not fully checked this out,but all my FPU are rated at 33Mhz.

It does conflict with accelerator(s),but I did solve the problem on one of test motherboard,but for now their all sit in sockets. Matter of fact two of my motherboard are almost completely socketed but FastATA III/IV is not affected as it connected in a different way so I just insert into rom socket nothing else (single board).

NOTE: during testing two soft reset was required when blizzard card was active,but only one soft reset was required to re-activate card when FPU is on motherboard so a simple way is to have FPU in a socket if it is conflicting with accelerator(s).

[desiv]

Yeah, I read a blog post by a guy who did that..
I was toying with the idea of doing it also, but he found out that he couldn't have the FPU on the Motherboard AND an ACA accelerator (which has no FPU).
I was kind of thinking it might be a fun project and at least enable me to run some FPU software (even if it was a slow FPU), but not if I can't use my ACA...

(can't find the link now, it's been a while since I saw that blog. I'll post it if/when I find it again)
Found it: https://www.facebook.com/AppysAmigaPage You have to scroll way down to see his FPU work..

desiv

[Lord Aga]

Originally Posted by delshay

The FPU on motherboard does work,I have it install as standard on my test motherboard. But I have never complete what I wanted to do with this along with 25Mhz 68EC020 which is also on motherboard of all my A1200(s) along with 60ns chip ram chips,not sure where I am going with this but is on my to do list.

FPU may can be clocked separately did not fully checked this out,but all my FPU are rated at 33Mhz.

It does conflict with accelerator(s),but I did solve the problem on one of test motherboard,but for now their all sit in sockets. Matter of fact two of my motherboard are almost completely socketed but FastATA III/IV is not affected as it connected in a different way so I just insert into rom socket nothing else (single board).

NOTE: during testing two soft reset was required when blizzard card was active,but only one soft reset was required to re-activate card when FPU is on motherboard so a simple way is to have FPU in a socket if it is conflicting with accelerator(s).

Whaaa...
Picspicspicspics

[LTAC]

https://www.facebook.com/media/set/?...6499869&type=1

[Steve T]

Originally Posted by desiv

Yeah, I read a blog post by a guy who did that..
I was toying with the idea of doing it also, but he found out that he couldn't have the FPU on the Motherboard AND an ACA accelerator (which has no FPU).
I was kind of thinking it might be a fun project and at least enable me to run some FPU software (even if it was a slow FPU), but not if I can't use my ACA...

(can't find the link now, it's been a while since I saw that blog. I'll post it if/when I find it again)
Found it: https://www.facebook.com/AppysAmigaPage You have to scroll way down to see his FPU work..

desiv

Ah, if there's a conflict then this is a shame, I have ACA as well, would be nice to have a system with this accelerator and FPU (yes, even if its not the quickest). Interesting stuff though.

[mfilos]

Yes it does conflict and you can't do much stuff about it sadly.
Pitty that Jens haven't putted FPU support on his ACA line of accelerators (meaning putting the socket).
Despite most users wouldn't need it as they don't use software that utilizes it, there are users that would benefit much from the FPU... anywayz...

[duga]

If you want FPU; buy 040 or 060 instead.

[Lord Aga]

Originally Posted by LTAC

https://www.facebook.com/media/set/?...6499869&type=1

Whoa man that's cool
How come this wasn't a popular mod back in the days ?

[delshay]

Why did you remove the centre of the socket? That part gives the socket strength and also has the marking pointing towards pin 1.

FPU with Blizzard does work extra reset is just needed,but I had a modification on my Blizzard for it to work,but was never completed.

Boot from cold is normal,its just when card is disable/enable by holding down the 2 key when doing soft reset when its re-enable it requires two soft reset,disable is normal just one soft reset if I remember correctly.

Reset maybe the other way round as posted,but it does work here with modification on Blizzard.

[Steve T]

Originally Posted by mfilos

Yes it does conflict and you can't do much stuff about it sadly.
Pitty that Jens haven't putted FPU support on his ACA line of accelerators (meaning putting the socket).
Despite most users wouldn't need it as they don't use software that utilizes it, there are users that would benefit much from the FPU... anywayz...

I guess it was simply a cost thing with the ACA's. Shame by design it also disables the one on the mobo too.

Here is the statement about it by Jens as copied from Appy's facebook page:

The FPU would have to be on the "other side" of the data bus drivers/latches, and yoiu'd have to do quite a few changes in the logic of the accelerator board. The ACA1232 generates a BERR signal on every FPU access, so the ROM knows that there is no FPU. Further, BERR is generated on other occasions where a watchdog "bites". Even if you generate your own FPU select signal, interrupt the BERR line and gate it with your logic, you'd still have no luck, as the DSACK0/1 lines are push/pull in my design for stability reasons. A second DSACK source (such as the FPU) would require your own logic in the CPLD and some strong pull-up resistors that ultimately make the design unstable. In other words: Better don't try it.


Bah! foiled again!

[desiv]

Originally Posted by delshay

Why did you remove the centre of the socket? That part gives the socket strength and also has the marking pointing towards pin 1.

From the text on his page with the pic of the socket with the base removed:

Removal of the Base to ease soldering.

desiv

[delshay]

The centre of the socket does not need to be removed. There are two or three ways to get it installed. All the sockets here on my motherboard have the centre intact no damage whatsoever. You just need a steady hand and smaller soldering tip.

[imigger]

I did this mod on mine and upgraded cpu ,works great with a 8mb memory card with no fpu onit ,works great on3d stuff.

[gdunlapsd]

Sorry for the necrobump of this old thread, but I wanted to mention that I did this mod and it works great, and gets along just fine with my TF1230 accelerator; even at 14mHz it's a big improvement over CPU math.

But that's not all; the 68882 clock is asynchronous, so I isolated its clock pin (pin 11) and wired it to E131R for the 28mHz clock signal, and it's now running nicely at 28mHz!

When I have time, I'll wire up a dedicated, faster clock crystal to it.

[skan]

Originally Posted by gdunlapsd

Sorry for the necrobump of this old thread, but I wanted to mention that I did this mod and it works great, and gets along just fine with my TF1230 accelerator; even at 14mHz it's a big improvement over CPU math.

But that's not all; the 68882 clock is asynchronous, so I isolated its clock pin (pin 11) and wired it to E131R for the 28mHz clock signal, and it's now running nicely at 28mHz!

When I have time, I'll wire up a dedicated, faster clock crystal to it.

That's daaaamn nice! Pure Amiga spirit!

[gdunlapsd]

Originally Posted by skan

That's daaaamn nice! Pure Amiga spirit!

Thanks! I just wanted to let people know that this is a very viable option!

Someone asked for more details, so I'll post here for everyone's benefit.

Chris Edwards shows adding an FPU socket on his Youtube channel here:

[ Show youtube player ]

I used the Amiga PCB Explorer site (https://www.amigapcb.org/) as a reference.

Here's how I isolated the FPU clock pin:
The CPUCLK trace runs under the board to the expansion connector, with vias to the FPU and CPU along the way. Because the FPU via was covered up by the socket I had already installed, I cut the CPUCLK trace just on either side of the FPU clock via, and ran a bypass wire to reconnect the signal to the CPU clock via (and beyond to the expansion connector).

Then I ran a wire from the FPU clock via, around the edge of the motherboard to the resistor at E131R, on the leg toward the rear of the motherboard which connects to Budgie pin 94.

Hope that makes sense! Sorry, I didn't take any pictures at the time - wasn't sure it would even work - and my Amiga's all back together.

BTW, my MB revision is 1a; don't know how much later versions vary.

[eXeler0]

@gdunlapsd If there was an elegant way to do a mod when a 40 or 50MHz Crystal then I'm sure it would be a popular mod ;-)
Just got me thinking what happens if you have an onboard FPU and a TF1260 with an EC060 ;-)