Clearing up acronyms

[3246251196]

When it comes to amiga I hear lots of acronyms. For instance, I was looking at an accelerator card which included the letters FPU - now, I have heard of CPU, GPU, PPU etc etc... but not FPU

What is (an) FPU? And, does it come with an accelerator card (where I am right in saying the A Card also potentially includes memory as well as increased Proc' speed)

[beller]

FPU=Floating Point Unit

The FPU is a chip that went with the 020s and 030s as a math coprocessor. You can use most accelerators without one but it does speed up math operations if it's installed,

Bob

[3246251196]

ok. so i have a standard A1200 (with the HDD however) with a 68k20 - on my mobo do i have a FPU now?

[adz]

3246251196 wrote:
ok. so i have a standard A1200 (with the HDD however) with a 68k20 - on my mobo do i have a FPU now?

No, but most RAM expanion cards have a FPU socket that can accept a 68881 or 68882, there is no FPU socket on the A1200 motherboard.

[Oliver]

FPU's are also not just for Amigas.  Any type of CPU (or micro) may have an FPU.  Some processors have them built in as part of their instruction set, while others have to emulate the maths instructions (slowly).  For example, AMD Athlons have the FPU instructions built in, while Durons do not.  x86 machines are no longer fitted with a capacity for FPU expansion - they either have them in the CPU or not at all.  External FPU's are also called maths-coprocessors.  If you do anything requiring floating point mathematics, the FPU is invaluable.

[Matt_H]

there is no FPU socket on the A1200 motherboard.

There sort of is. Commodore planned to make 1200s available with an onboard-FPU as an option, but never did. With some serious work, one could probably be soldered in. There's probably some other areas on the board that need modification too, much like Doobrey's PCMCIA access LED mod.

As for math operations, they're mostly relevant for things like rendering software and some processing libraries (mpega.library). Most recent programs take advantage of them. For a retro gaming Amiga setup, one probably isn't important.

[3246251196]

-so these accelerator cards: they include more memory (even have spaces to add more memory)?.

-they can (or DO) include an FPU?

[Oli_hd]

-so these accelerator cards: they include more memory (even have spaces to add more memory)?.

Yep, accelerator cards (Ones with CPU's on them) can normally take up to 32Meg and some times 128 or 256Meg.

A card like the A1208, which is a memory upgrade, not a CPU upgrade, will have a slot for up to 8Meg and normally a socket for an FPU.

-they can (or DO) include an FPU?

They can and sometimes do include an FPU, its normally right next to the CPU, if there is an empty socket chances are it doesnt have an FPU, if there is what looks like a smaller CPU by the side of the main CPU then thats the probably the FPU

Only CPU upgrades with 68020 or 68030 CPU's will have a space for an FPU, cards with 68040 or 060 CPU's on them have the FPU built into the CPU or not at all.

Amiga-Hardware link to the Viper 1230
The pictures on the above link show a CPU upgrade with a 68030 CPU, the top picture shows the CPU next to the connector, a gap where a PGA (Pin Grid Array, a chip with lots of legs pointing down) would have gone and then next to that a socket for a PLCC (plastic something chip carrier ;-) the one with pins at each side of the chip and none under it) version of an FPU, that socket has the FPU in it.

Below that is the "standard" PGA style FPU next to the larger 68030 CPU.

[Martyn]

Oliver wrote:
For example, AMD Athlons have the FPU instructions built in, while Durons do not.

:-o Durons most certainly do! The last x86 processor that didn't have a built-in FPU was the 80486SX circa 1989!

The difference between Athlon and Duron was cache size.

Martyn.

[adz]

Matt_H wrote:

there is no FPU socket on the A1200 motherboard.

There sort of is. Commodore planned to make 1200s available with an onboard-FPU as an option, but never did. With some serious work, one could probably be soldered in. There's probably some other areas on the board that need modification too, much like Doobrey's PCMCIA access LED mod.

Hmmm, never knew that, thanks for the tid bit of Amiga trivia :-)

[_yak_]

http://www.amiga-hardware.com/download_photos/a1200mb_rev1d4.jpg

On this shot of A1200 MB you can see a spare place for an IC next to the CPU and below the ROMs. The place is labeled U0. It was meant for FPU probably.

[3246251196]

so its possible to get an Accelerator card with:

1. A Memory Upgrade?

2. A CPU Upgrade?

3. An FPU Upgrage

4. If this is true, what happens to the CURRENT CPU in the MB?

5. The memory on the Accelerator card is now Grphics mem in WB?

[Oli_hd]

so its possible to get an Accelerator card with:    1. A Memory Upgrade?    2. A CPU Upgrade?    3. An FPU Upgrage

An "Accelerator" is techincally anything that makes your Amiga go faster, there have been Amiga 500 memory cards sold as "Accelerators" but the common meaning of the word is a CPU upgrade, not a Memory upgrade or FPU upgrade.

You can get an "upgrade" that is just a memory card and they often have a battery backed up clock and in the case of the A1200, an FPU socket.

4. If this is true, what happens to the CURRENT CPU in the MB?

It is told to shut up and get off the bus by a logic chip on the CPU upgrade.

5. The memory on the Accelerator card is now Grphics mem in WB?

No, the memory on the Accelerator card is always "Fast" Ram.
The "Chip" (Or Graphics) Memory is 2Meg as standard on the A1200 and can not be upgraded further.

[Oliver]

:-o Durons most certainly do! The last x86 processor that didn't have a built-in FPU was the 80486SX circa 1989!

Ooops, sorry, my bad.  Got that from a salesman.  Never bought either of those chips.   :sealed: I'll just shut-it now.

[biggun]

Many years ago when you could put just a few hundret thousand transistors into a chip
it made sense to have two chips one for general computing (cpu)
and one extra for scientific mathematical stuff.
90% of the programs and people won't need the FPU and
could save money by not buying it.

Today an average chip holds millions of transistors so reducing
its size by a few hundret thousand transistors does not make any sense.
So today all mainstream CPUs include FPU and MMU.

MMU (memory management unit) is needed for virtual memory and memory protected.
FPU is used for scientifyc math. Today 3d games use it too.

Both FPU and MMU were optional in the Amiga days.
99% of all applications don't use them at all.

The 68030 was the first 68k who included the MMU.
The 040 and 060 both included MMU and FPU into the chip.
But there were low cost version of 040 and 060 (LC/EC) not including them.

Having an FPU will not speed up your normal applications at all.


Cheers
Gunnar