Using a 68060 with an external FPU
 

I was just wondering with the new 68060 cards that have been coming out and the scarcity of the 68060's with an internal FPU. Would there be a way to design a board that can use the 68882 FPU with the 68060 with out the internal FPU. I have no idea of hardware design but the 68882 seems to be more plentiful than the full 68060 CPU's. Just an idea

Thanks
Dan

The 68060 doesn't support using external FPUs so it won't work unfortunately...

I had the same question earlier this year. Alas, it's not possible.
See: http://eab.abime.net/showthread.php?t=110700

The 68060 (and 68040) lacks the coprocessor interface the 68020 and 68030 had, so you cannot connect a 68882 to a 68040 or 68060. The best you could do is to connect it as an I/O device, and manually banging its interface, which requires a software interface and is going to be very slow. Talking about speed, even natively the 68882 is rather slow compared to the 68060 internal FPU.

Some of the earlier XC68060 processors marked LC/EC actually have FPUs & MMUs in them but the FPU/MMU are not guaranteed to work at the rated speed (or at all).

It is only later that the 68060 got dedicated LC/EC parts where the FPU/MMU were either disabled or not present.

My experience with early EC/LC chips is there must have been more demand for LC/EC parts than there were failures and so fully functional chips were sold as LC/EC. (Because I've seen so many say theirs is fully functional)

There is no way in SW to distinguish these parts from FULL 060s which can be problematical if you have one where the MMU/FPU doesn't work

if you buy any accel with a 060 without fpu then you are doomed forever
also the 060 built in fpu is around 20x faster than the 68882 at 50mhz
and there is no possibility to connect it


if there is a shortage of full 060 then a full 040 is a far better option than any eco version of the 060

Why? Which applications really need a FPU?

Only really demos. Maybe Quake?

Quake exists in non-FPU version on other systems and even the softfloat version on the Amiga is mostly playable when running at 100 MHz (TF1260)... many other things would work fine if people bothered to compile with the -nofpu switch.

using a 68060 with an external FPU
 

Back in the day I was one of the earliest Blizzard 1260 buyers, (ordered from Germany through mail order as soon as it was released, I didnt wanna wait for it to be released in Sweden). I did it to **dramatically decrease** render times in Imagine 3d. (about 500%) speed increase over a 50Mhz 030 + 50 Mhz 68882 FPU.

These days most people wouldnt torture themselves by rendering on Amiga although there are still some hardcore Lightwave fans out there who do it.
So why FPU?
As other mentioned, lots of 060 demos expect a FPU.

If you dont care about demos…?
About Quake.. When we get to those mid 90s PC release, they are available on other platforms and generally run much better even on a vintage Pentium 133. Bit If you still wanna explore those ports on Amiga, you probably want FPU.

But mainly, for me anyway, its nice to know that with a full 060 i will be able to run pretty much all software available for Amiga as opposed to having a really fast 060 Amiga which cant run all high end software.
External FPU could in theory help, but it would never be the same as a full 060.

some games like quake,quake 2, duke nukem 3d yes use it and don''t work without it
apps as "simple mail" , mp3 encoders as lame etc

also if you use a Mac 68k emulator as shapeshifter or fusion, then you are more limited because lot of Mac apps requires FPU

on the other way the 68882 is really slow and obsolete compared with 040 and 060 built in FPUS
using the 68882 quake or duke nukem will work at 1 or 2 fps, (photo play)

Descent also, without it it just goes below of the playable level.

Yet, on LC060 at 100 Mhz you will get 9-10 fps and this is in softfloat.

There are solutions, but they need implementing.

LOL, overreact much?

Depends very much on what you're doing. A full '040 is quite a bit slower than a full '060 for most things, and if you're interested in demos that need an FPU, they'll likely be too slow on a full '040 anyway.

While there are a small few games that do require an FPU, they're hardly a dealbreaker for people who don't have much interest in playing ports of PC games that run far better on that platform anyway.

I haven't noticed a need for an FPU when using SimpleMail.

Encoding MP3s on the Amiga falls into the same category as rendering - doing anything serious is so slow that it makes far more sense to do it on another platform - even if under emulation. Listening to MP3s at least is something that can be done on an '060 (and integer decoders are often faster than ones using the FPU), whereas with a full '040 you need to compromise on the decoding quality.

The Mac side can use a soft FPU, though that will of course be slower.
They're all quite niche use cases all things considered though, hardly the awful "doom" you speak of that users would find themselves stuck in.

The single biggest reason for a full '060 these days is to be able to run demos. After that, you're into smaller and smaller edge cases, and while these uses are clearly important to a few people like you, that doesn't mean they're automatically important for users in general. To counter your own individual requirements, I can tell you that, far from being doomed, with current '060 prices I have saved myself hundreds of pounds by using an LC060 instead of a full '060 and haven't once found myself missing the FPU.

What I thought would be cool would be to use an FPGA as a gatekeeper that routed the non-fpu instructions to the stripped 68060 and send the fpu instructions somewhere else (ARM maybe). Anyway, apparently it's not possible or practical but it's still a cool idea :)

IF you're going to that trouble you may as well use a PiSTorm32 Lite as an alternative to a 68060

Starting to drift slightly OT here, but does that thing even emulate 68060? Or is it a hyper-fast 68000?

The PiStorm can do everything Musashi (or Emu68) can do:

Musashi is a Motorola 68000, 68010, 68EC020, 68020, 68EC030, 68030, 68EC040 and 68040 emulator

So no explicit 060, but since the 020-040 support more opcodes that's irrelevant

Emu68 tries to implement the full 020+fpu set.

Full 68060 with FPU and MMU? Great!
Where can I buy it? I can’t find it anywhere to purchase…