Considering replacing 68881 with 68882

[B14ck W01f]

I would like to purchase a MC68882 FPU for my MBX 1200z expansion board I have installed in the A1200 , to replace the existing MC68881 installed on the board. What I can see, there are different versions of the FPU, including:

MC68882FN16A
MC68882RC50A
MC68882RC25A
MC68882FN33A
MC68882FN20A
MC68882FN16A

Which one of these should I get for it, or doesn't it matter?

[alexh]

You won't find anything (that's any good) which will utilise a 68882 (or 68881) on a card like that.

Has to have RC at the end to fit the MBX 1200z card

The RC means it has a PGA package

[glenn]

As Alexh is pointing out, you have to use a PGA FPU, that means it have to be a RC or RP version, RC = PGA ceramic, RP = PGA plastic (FN = PLCC)


68882 is indeed much faster than 68881 at the same clockspeed, but what are you going to use it for with just a 020EC ?

Another thing is that both 68881 and 68882 is extremlig overclocking friendly, most paerts that are stamped with less than 50MHz is fully capable of running 50Mhz, or even more, I have been using a 16Mhz FPU in 66MHz without problem for years

[Zetr0]

@glenn

Another thing is that both 68881 and 68882 is extremlig overclocking friendly, most paerts that are stamped with less than 50MHz is fully capable of running 50Mhz, or even more, I have been using a 16Mhz FPU in 66MHz without problem for years

running at 66MHz it would be wise and advisable to suggest a heatsink, also while I think about it - heat will likely be traped (and build up) if the FPU is on the underside of the Amiga - like it is on the MBX 1200z, as opposed to the top side (under the keyboard) like the Apollo Mk3 030.

[kolla]

Er... there's plenty of software that makes use of an FPU, and on a low-end configuration it makes a big difference.

[slaapliedje]

It's too bad they don't use the PLCC ones, I have two of them just laying around that are 68882 at 50mhz. I bought five of them, put one in my Atari TT030 and one in my Atari Mega STe, and sent one to a guy that had his burn out in his TT030. So I have two left.

They were only like 10 bucks! Not that I've had much time to do much with my older computers lately.

slaapliedje

[B14ck W01f]

Originally Posted by kolla

Er... there's plenty of software that makes use of an FPU, and on a low-end configuration it makes a big difference.

List, please?

[Zetr0]

@B14ck W01f

From the top of my head - when I got my first A1200 upgrade (a Gastiener 8MB + 40MHz FPU) Re: Hawk Reference Board - these are the titles I opened up -

Applications:
Imagine (3D POV renderer) (there is an non-FPU version)
Real 3D (there is an non-FPU version)
Lightwave (there is an non-FPU version)
Vista Pro (there is an non-FPU version)


Games:
Quake
Doom (there is an non-FPU 32bit INT version)
THX (takes advantage of the FPU)


Thats from the top of my head, there are some graphics viewing programs on workbench that use and FPU to help speed up rendering JPEG's and MP2's etc.


Performance:
When running Imagine 3.1 - FPU version for the first time I was blown away, what used to take my A1200 3 minutes to "Quick Render" was now achieve in about 1 minute due to the 40MHz MC68882FN40 =)

I hope that helps

[glenn]

But all of those softwares is not that useful on a 68EC020, FPU or not..

Also, using raytracers on the Amiga today is not very useful at all, I have used Real3D a lot in my days (1.x to 3.x), but that was back in the days my 68060 50MHz was around the speed of the current PC's (P90), today a dumpster found PC render a preview image with lightsources and textures in realtime, even a very fast classic Amiga would take hours to render only one frame of this 60Hz preview.

[kolla]

You are right, Amiga computers are not useful at all, why are we here.

[alexh]

Originally Posted by kolla

Er... there's plenty of software that makes use of an FPU, and on a low-end configuration it makes a big difference.

Like what?

[alexh]

Originally Posted by Zetr0

there are some graphics viewing programs on workbench that use and FPU to help speed up rendering JPEG's and MP2's etc.

Are you sure? I was sure these algorithms were fixed point

[trixster]

Originally Posted by glenn

but that was back in the days my 68060 50MHz was around the speed of the current PC's (P90)

Using Quake as a reference point which is pretty reliant on fpu speed, I've found that an 80mhz 060 lies somewhere between a P60 and P75. It's not P90 speed.

[Zetr0]

Originally Posted by alexh

Are you sure? I was sure these algorithms were fixed point

Hmmm I am pretty sure there are some workbench / graphical decompression routines that benefit from an FPU. I will have to hunt for the thread I read this in. There was also mention of a FONT creating / conversion program.

Originally Posted by trixster

Using Quake as a reference point which is pretty reliant on fpu speed, I've found that an 80mhz 060 lies somewhere between a P60 and P75. It's not P90 speed.

While it might be something in those performance values, its fair to say that Quake is not as optimized for the 68k moto compared to the x86.

[idrougge]

Originally Posted by Zetr0

There was also mention of a FONT creating / conversion program.

TypeSmith?

Originally Posted by Zetr0

While it might be something in those performance values, its fair to say that Quake is not as optimized for the 68k moto compared to the x86.

Really? I thought Clickboom worked hard on optimising Quake.

[kolla]

List of software that makes use of FPU and that is relevant to use on low-end Amiga?

Well, I remember well having just an A1200 without FPU, and how liberating it was when I finally got one.

* Image processing software - are there any that don't have 68881/68882 support?
* Music software, soft-synths, TB303 emulators, sample processors
* Office software, spreadsheets, DTP, graph plotters
* Science software, math (calculus, fractals), astronomy, chemistry, physics
* Alternative math libs (used by datatypes, rexx support libs etc), ixemul

Just for fun I search Aminet for packages that have "FPU" as content, many "false positives", but it gives you an idea:

http://aminet.net/search?readme=FPU&...gaos&sort=path

[kolla]

Originally Posted by alexh

Are you sure? I was sure these algorithms were fixed point

They exist as both. But, why hog an already slow 020 with something a 882 can do so much quicker? Especially a 882 clocked higher. Also, the FPU leaves the poor 020 free to do other things in the meantime.