Motorola 68060 FPGA replacement module (idea)

[freqmax]

In another thread the issue that there are too few fast Motorola 68060 CPUs around came up. But that a solution could be to join a male socket and a FPGA on top of that. Much like the 486- or pentium  overdrive solutions for the x86.

The MC68060 datasheet provides the PGA 206 pinout at page 356. And the frequency span is 0 - 75 MHz. Power (p328, p344) requirement is 3.3V +/- 5% @ 2A with 5V compatible I/O. There has not been any QFP variant on the commercial market, ever?

So this is what the FPGA has to be able to work with. Some kind of onboard DC/DC circuit will be needed. The voltages of iVDD, EVDD, PVDD and CVDD is unclear especially in a mixed 040/060 environment. So the question becomes, can a powerfull enough FPGA that implements 060 make do with 6.6 W ? and will the mechanical size be within limits? otherwise circuit board stacking may be needed.

Btw, with some additional PGA-114 (020) and PGA-132 (030) to PGA-206 adapter it could be used as a upgrade option for those CPUs too.

OT Found while searching:
a68k.de - Overclocking Amiga.pdf

[freqmax]

Perhaps a boosted 030/040 core pretending to be 68060 might be as good from a software point of view?

It's mainly a compatibility and perfomance issue. It doesn't have to be 060 in its heart.

[freqmax]

You mean as in ASIC silicon? that would cost at least 40 000 USD, proberbly around 400 000 USD.

The function is not protected as the patents has expired. However perhaps the instruction set opcodes are? but I doubt that to as there exist many other projects in this area without legal problems.

[freqmax]

Its waaaaaaaaaaaaay to hard to make the signals on the pins perfectly match a real 68060.

Where is that stated as a requirement?
(it's only needed for A500 and A1200 setups where some software rely on hw specifics)

My original idea was to provide a solution for those that want FPGA Arcade (MikeJ) with add on board and want to make use of a fast 68060 CPU but just can't get one.

@ChaosLord, How can you be absolutely sure there's no 1333 MHz capable RAM ..?
(but signal integrity will be a pain)

[freqmax]

I forgot about RAM latency, but wouldn't RAM at 1333MHz and CL9 still be able to max out a 100MHz CPU?

Would there be any advantage to using graphics memory in this application? (i.e. GDDR4/5 rather than DDR2/3)

A DRAM with the CAS latency would need 9 clock cycles before it would give you the data you requested. Ie at 133 MHz. But you also have to add RAS/CAS delays etc. Otoh you can use those 9 cycles to transfer other data. But in practice it would max out a 100 MHz CPU.

GDDR gives no real benefits in this application.

SRAM has the backside that it eats clock cycles when you least expect it. Better to deal with the real thing. Tough but true

[freqmax]

In the FPGA Arcade schematic:
http://www.amiga.org/forums/showthread.php?t=55885&page=54
http://www.fpgaarcade.com/common/fpgaarcade_replay_b01_schematic_a2.pdf

The RAM is specified as "DDRx16-TSOP66" (46V32M16) so MEM_DQ(0..15) will transfer 16-bits on positive flank and another on the negative flank. Thus 32-bits for each clock cycle.
(PCB picture)

So that type of DDR RAM is only 2nd generation. When the current ones are at least 5th generation.

@ChaosLord, a 68060 pin compatible replacement that is code compatible and as fast as possible. No "extra" cables going places that makes you scratch your head in "not found socket" ways.
(ie not cycle exact)

[freqmax]

A quick look at the 68060 technical data suggest it needs like 16 kB cache RAM. It should be possible to handle within the FPGA "BlockRAM" (as Xilinx call it). So likely no need for extra RAM. Btw, don't forget the cache coherency issues so that disc DMA and CPU don't disagree on what is in the memory..

Actually a 020 core will be smaller (I hope) and thus suffer less internal gate-to-gate latency. So it should perhaps be able to clock fast enough to outperform a 060 @ 75 MHz.

Btw, does it exist any faster than 75 MHz 68060 ..?

[freqmax]

10  It had to be written, rewritten, rerewritten to be optimized, oops now there are a ton of bugz, oh crap this is getting really tedious I think I will take a vacation ok now where did I leave off at... oh yeah gotta fix all these bugz hold on if I rewrite it this other way it will work better when we add the MMU later lather rinse repeat  goto 10

Solution, don't try everything at once. Release the source, let the crowd improve step by step by many people. Thus no overheated brain

This isn't a problem if you can prefetch and burst fill your cache.

*drumbeat* .... IF

Software has a tendency to jump all around the place..

[freqmax]

designed by a 200th TechMage.

What do you mean with that?

[freqmax]

100 GBP.. seems they have fallen.

But the main pain is the chip package...!

[freqmax]

Asfair, the shortage is on 060 that are 75 MHz or faster, has MMU/FPU (full version), without chip bugs.

50 and 66 MHz variants are supposedly quite easy to get.

[freqmax]

ARM/MIPS/Alpha etc.. is good enough and has an orthogonal programming ISA, low power etc.. compared to x86. Feeding a power parasite from a 3.3V 2A supply is perhaps not optimal.

[freqmax]

P-p-p-p-plase lets get on track here. One needs some onboard DC/DC and a FPGA. Anything else is just a burden that won't benefit the design goal.

The addition of any ASIC CPU will require lot's of scarce I/O on the FPGA, more power, more mess circuit board routing, more debugging, complicated sourcing, larger FPGA which cost more and is harder to source.. and harder to solder, additional RAM, boot ROM, etc. Just because you can do something doesn't mean it's suitable.

[freqmax]

What does 68060.library and setpatch do?

(and what is Fusion?)

[freqmax]

There's already some hybrid 68020-030-040-060 core in the FPGA Arcade.

No need mess with proprietary cores with requirement for specific FPGAs. Nor any Coldfire incompatibilities.

A practical issue is that due to the through-hole nature of the 68060 PGA socket any PCB will be occupied by solder pads from the pins. A solution is to put double row a straight pin 1.27 mm header around the PCB edges. Such that a another PCB can be mounted on top and the space be used for FPGA, DC-DC and EEPROM.

A plain PGA-206 socket will leave approximately 20.3 x 20.3 mm and the XC3S1600E -FG320 used in the FPGA Arcade uses 19 x 19 mm which leaves a margin of 0.66 mm around the edges. Tight! And ofcourse there's then no space for the DC/DC and EEPROM which is essential for operation.

Btw, it seems perhaps x86 motherboard "Socket 3" fits as socket for 68060.

FG320:


PCB stack (illustration):


DC/DC (illustration):