Possible to choose which FPU?

Discuss CT60/CT63, CTPCI, SuperVidel and EtherNAT hardware here.

Moderators: Mug UK, moondog/.tSCc., lp, [ProToS], Moderator Team

mzry
Captain Atari
Captain Atari
Posts: 390
Joined: Tue Jan 26, 2016 12:39 pm

Possible to choose which FPU?

Postby mzry » Thu May 17, 2018 6:08 am

Just wondering if you can tell the 060 Falcon to use the 68882 fpu instead of its 060 internal FPU. I noticed in some mint installations they have 68882.prg and I have always wondered if this is what it does?

And why would anyone want to... I hear you ask. Well I remember DML telling me that a lot of his FPU programming is only compatible on a real 68882 and the one inside an 060 isn't feature complete.. so for compatibility would be the reason.

Thx
Falcon ct63e 060 - 256mb ram - phantom bus and dsp accel // Atari TT - Thunder and Storm IDE 64mb ram - SCSI2SD - ET4000 vme graphics

mikro
Atari God
Atari God
Posts: 1565
Joined: Sat Sep 10, 2005 11:11 am
Location: Kosice, Slovakia
Contact:

Re: Possible to choose which FPU?

Postby mikro » Thu May 17, 2018 7:13 am

No, that's for Milan's 68882 FPU emulation, AFAIK. You're stuck with what the 060 and its software emulation package provides.

ThorstenOtto
Captain Atari
Captain Atari
Posts: 295
Joined: Sun Aug 03, 2014 5:54 pm

Re: Possible to choose which FPU?

Postby ThorstenOtto » Thu May 17, 2018 7:16 am

mzry wrote:Just wondering if you can tell the 060 Falcon to use the 68882 fpu instead of its 060 internal FPU.


Simply put: no. It's the processor who decides how to drive an FPU unit. 040 will use its internal version, 020/030 will use an external interface. Only thing you can do is to disable the internal FPU, but that does not mean an external FPU is used instead.

I noticed in some mint installations they have 68882.prg and I have always wondered if this is what it does?


Such programs are just compiled for an FPU. The instruction opcodes for 030 & 060 are the same.

I remember DML telling me that a lot of his FPU programming is only compatible on a real 68882 and the one inside an 060 isn't feature complete.. so for compatibility would be the reason.


That's why you usually need an FPSP package that emulates the missing functions. I think in practise the missing functions are not used a lot.

Moulinaie
Captain Atari
Captain Atari
Posts: 184
Joined: Wed Feb 01, 2012 9:34 pm

Re: Possible to choose which FPU?

Postby Moulinaie » Thu May 17, 2018 7:36 am

mzry wrote:Just wondering if you can tell the 060 Falcon to use the 68882 fpu instead of its 060 internal FPU. I noticed in some mint installations they have 68882.prg and I have always wondered if this is what it does?

And why would anyone want to... I hear you ask. Well I remember DML telling me that a lot of his FPU programming is only compatible on a real 68882 and the one inside an 060 isn't feature complete.. so for compatibility would be the reason.

Thx


If you have a look at the last test at the bottom of this page: (test 6 FPU)
http://gtello.pagesperso-orange.fr/kronos_soft.htm
You'll notice that the CT60 is not always so good at floating point. Especially with TOS.
I was thinking of using the 68882... but it seems impossible.

Guillaume.

User avatar
Greenious
Hardware Guru
Hardware Guru
Posts: 1194
Joined: Sat Apr 24, 2004 5:39 pm
Location: Sweden

Re: Possible to choose which FPU?

Postby Greenious » Thu May 17, 2018 9:22 am

No, it's not possible.

The reason is that the CPU/FPU combo with 020/030 and 6888x is essentially a single CPU to the system, just as the 68060. Since these are not designed to work in tandem, or in a multiprocessor system, only one can run at any given time, and they have no means to access eachother.

Although I suppose that in theory you could probably hook up a 6888x to the 060 as a peripheral device, like it is done on Mega STE and with 68000 math co-processor cards.
Updated my guides as of june 28th, 2016. Check'em out and feedback!
viewtopic.php?t=5040


Social Media

     

Return to “CT60 / CT63 Area”

Who is online

Users browsing this forum: No registered users and 1 guest