Need help! A3660 without FPU and OS3.9

[Mathesar]

Originally Posted by Chucky

@Mathesar some days ago I did a video soldering a TF1260. using your design.
I by misstake had too much solder on the oscillator and made a short between GND+3.3V

this started a fizzeling sound from the DCDC. have investigated some. what are the diodes there for? they get 150+ degrees in such short (my FLIR stops at 150). removing them and board will still work but never go to dangerous temperatures.

so at the moment I would recomend removing those diodes.

Oops!, yes if you short the output the diodes will get the full 5V over them and get very hot indeed! The diodes are there to limit the voltage difference between the 68060 IO and VDD to max 2.1V. If the 5V comes up and the DC/DC converter is slow to start it might happen that the 68060 gets 5V levels on its data/address/whatever pins while it has no +3.3V power yet. This is not allowed and the datasheet recommends the diodes to prevent that.

However, I think that in practice the +5V ramps up so slowly that the DC/DC converter has enough time to start up.

So, the diodes need to be there for safety as per motorola's recommendation but are probably not needed in practice.

[Chucky]

When building and testing 3660s. I usually put in a header for the regulator. so I can use 040 or 060. so I can put on one DCDC to get 3.3V to test 060s..

MANY times I have fotgot to put in the 3.3 board.. even for minutes measuring if I get data until I notice "DAMN no 3.3V". been on for even 1-2 MINUTES. no dead 060.

[Mathesar]

Originally Posted by Chucky

When building and testing 3660s. I usually put in a header for the regulator. so I can use 040 or 060. so I can put on one DCDC to get 3.3V to test 060s..

MANY times I have fotgot to put in the 3.3 board.. even for minutes measuring if I get data until I notice "DAMN no 3.3V". been on for even 1-2 MINUTES. no dead 060.

Yes, these old chips are made to last. They don't make them like that anymore.

BTW, my 3660 is still going strong
I did do a small modification though (yet again). My A3660 would only run on the 5ns delay line setting (10ns would only work after a manual reset but then FAST ram was gone). However, I got the occasional SCSI problem, especially after the computer had been running for a while. So, I replaced the delay line to get me about 8ns of delay. That solved all problems.

[salocinx]

Originally Posted by Mathesar

BTW, my 3660 is still going strong

Hi Mathesar.

First of all many thanks (!) for sharing your knowledge about the A3660 using with 68LC060 non-FPU on a Amiga 3000. I am currently setting up the same setting Since I already had quite some SCSI issues with my A3000 using the original SCSI controller chip, I replaced it with a AM33C93A-16PC SCSI controller IC, which solved a lot of problems using more SCSI devices on the bus than just the built-in hard-drive.

Now moving to the A3660 with 68LC060. I have read the entire thread. Beside the hardware issues (I will check the 3.3V rail with my cheap oscilloscope as well before starting), I want to summarize the software side of your conclusions. Could you please give me some comments if I am right with my assumptions that I made from reading this thread?

1.) Using the Phase5 68060.library is the best option for using an LC060 CPU on the A3000D ?

2.) I need a special Kickstart ROM for my A3000 that contains a non-FPU version of the mathieeesingbas.library?

3.) When installing software, I unconditionally always have to select 020/030 versions (using 040/060 always expect an FPU and will lead to problems) ?

Not sure if I summarized everything. I woud be very grateful if you could give me a quick summary how to avoid issues using A3660+68LC060+A3000

Thanks you!

[Chucky]

if you want to use a LC cpu on the amiga this is the way:

on the 3660 no custom kickstart is needed!

I use the phase5 060 libs..
and after that. you treat the machine as if it was a 030 without fpu.. NEVER install 060 executeables.. just max 030 with no fpu.

and this will work fine.

[Mathesar]

Originally Posted by salocinx

Hi Mathesar.
Could you please give me some comments if I am right with my assumptions that I made from reading this thread?

1) I don't know whether that library is the best. The latest P5 library from Aminet does work with an 68LC060 though. I am using Thor's MMUlib package which also works (remember to install both the CPU and the MMU libraries or the guru will visit you..). What OS version do you use? I am running OS3.9 with setpatch 44.38. That setpatch loads the 68060.library directly. If not, you will have to use a dummy 68040.library (as used by Phase5) or a patched setpatch.

2) Not necessarily. The computer will boot just fine with standard 3.1 rom's. I use loadmodule from Aminet (https://aminet.net/package/util/boot/LoadModule) to replace the rom-based mathieeesingbas.library with a disk-based one. That works a treat. Not many programs use mathieeesingbas.library but some do and they will crash with the rom-based mathieeesingbas.library.
I use this line before my setpatch command:
c:loadmodule >NIL: mathieeesingbas_020 DOWNGRADE REVERSE NOREBOOT
Note that the NOREBOOT only works if you have some other patch in your user startup that already reboots the system. Otherwise loadmodule will have to perform the reboot. I am using the mathieeesingbas.library from the A1200/A4000 roms. That version is optimized for 020+ cpu's without FPU.

3) Yes, I always install max 030 versions. A lot of 040/060 optimized versions expect an FPU and will crash. There are exceptions however like the recent AmiSSL 4.5 and higher for which the 060 optimized libraries also work without an FPU. Mind you, if you ever need to remove your 060 card and you have a lot of 060 optimized stuff installed absolutely NOTHING works anymore. Been there, experienced that! Not fun :-)
Also, even with just 030 optimized executables the computer is still plenty fast compared to the standard 030/25MHz.

[Mathesar]

Originally Posted by salocinx

Hi Mathesar.
Since I already had quite some SCSI issues with my A3000 using the original SCSI controller chip, I replaced it with a AM33C93A-16PC SCSI controller IC, which solved a lot of problems using more SCSI devices on the bus than just the built-in hard-drive.

Good tip, had a quick look on ebay and there seem to be plenty available.
Will give it a try!

[salocinx]

@Mathesar: Thank you so much for the detailed answer! This information is highly valuable for me ! Yes, I am going to install Amiga OS 3.9 on my A3000D and I am sure I will mastering it according to your instructions. Just great - very happy

@Chucky: Thank you too! This is a great and easy-to-rembemer guideline for using the 68LC060 CPU on Amiga systems

[salocinx]

Originally Posted by Mathesar

Good tip, had a quick look on ebay and there seem to be plenty available.
Will give it a try!

I would have sent you one for free... Just let me know in case you have not yet ordered it.

I can highly recommend it, I am having much less SCSI bus problems since I installed it.

[reinauer]

Originally Posted by Mathesar

I did do a small modification though (yet again). My A3660 would only run on the 5ns delay line setting (10ns would only work after a manual reset but then FAST ram was gone). However, I got the occasional SCSI problem, especially after the computer had been running for a while. So, I replaced the delay line to get me about 8ns of delay. That solved all problems.

Would you please elaborate what you did there? Which delay line did you use?

[mech]

Nice job finding that problem. Its interesting to know. I have some early rev1.0 3660's that can be picky on just the 060 clock speed. I wonder if this plays a role also.

[trixster]

This is a very interesting thread, I’m not sure why I didn’t read it before! Good problem solving @Mathesar

[Mathesar]

Originally Posted by reinauer

Would you please elaborate what you did there? Which delay line did you use?

I think I used a DS1000Z-20. Each tap is 4ns so by using the second tap you get 8ns. However, it didn't solve my issue completely.
At first, back in 2019, after all the debugging with the mathieesingbas library, 68060.library and the powersupply was done I had a perfectly stable system. However, 1 year ago or so my SCSI started acting up. So I tried the delay line adjustment, I replaced the SCSI chip but all to no avail. Then I replaced RAMSEY.... And that fixed it!
I think Speedgeek mentioned once that the 040->060 adapter, which is basically built-in in the A3660 introduces too much skew between the pclk and the bclk. He also mentioned that Ramsey probably has the most problems with that. I think he is right. Even more so because my A3660 only worked (haven't checked since I replaces RAMSEY) with the delay set to 5ns. At 10ns the system would only boot after a few attempts and then fast RAM was gone. That also points to RAMSEY issues methinks.

Now that I replaced RAMSEY everything is fine again and I really enjoy the A3660 in my A3000.

[reinauer]

Thanks, Mathesar, I appreciate the insights...! Will try.