PAK68/3 floppy not working

[TheNameOfTheGame]

I have a thread going over at atari-forum detailing my attempt to get a PAK68/3 installed. I won't rehash the whole thing here. If you would like to read it, the link is http://www.atari-forum.com/viewtopic.php?f=15&t=37581.

Anway, the PAK68/3 is installed and running, however the floppy drive is not working when in 68030 mode. It works without the PAK installed and also if the PAK is installed but running in alternate operating mode i.e. using the 68000. Here is the hardware I'm using:

ultrasatan.png (630.46 KiB) Viewed 4946 times

I have to mention the ultrasatan hdd you see in the above picture also doesn't work in 68030 mode. Here are errors I get for the floppy and ultrasatan in 68030 mode:

pak_drive_error.png (389.94 KiB) Viewed 4946 times

us_no_drivec.png (327.5 KiB) Viewed 4946 times

I was talking to exxos about this and he recommended I start a thread here. Several other users at the atari-forum thread also report floppy issues when using the PAK so maybe a discussion here could help some others. Apart from the DMA/floppy issues, the system seems entirely stable; no crashes, screen glitches, etc.

Here is my DMA circuit for reference.

dma_circuit_raw_resized.png (1 MiB) Viewed 4946 times

dma_circuit_resized.png (228.74 KiB) Viewed 4946 times

wd1772_schematic.png (256.86 KiB) Viewed 4946 times

Any help would be greatly appreciated!

[PhilC]

My Pak works fine in a Mega ST4, no floppy problems or problems with the Ultrasatan but then I have carried out a mod that Exxos recommended by fitting pull-ups on the WD1772. I also had to change the DMA chip as mine had failed but was only obvious when everything was working together.

Anyway, try this and see if it helps:

https://www.exxosforum.co.uk/forum/viewt ... mod#p16364

[TheNameOfTheGame]

Oops, thank you for the link, but I should have mentioned I have read that thread already and tried the pull-up technique (I used 4.7k instead of 10k) but it didn't change anything. Maybe I needed 10k?

When I measure voltage I am getting 5.20v. This machine is using a picoPSU. The line drivers and bus terminations have been changed as recommended in the PAK manual. I have not changed the 7406 to a 74F06 in the floppy circuit.

[PhilC]

I'm using an exxos PSU and my ram is 4mb using the SOP adaptors in 1 bank of 1mb as this motherboard was from a Mega 1 originally.

Only other thing of note for me is that I am running the Pak at 40mhz and that I had messed around swapping out chips with new ones when originally trying to diagnose my floppy issue before fitting the Pak.

What about the rest of the board pull-ups? exxos has recommended these be changed for reliabilities sake on some machines BUT i've also not done this and mine works fine.

Chips replaced were YM2149 and the MFP68901 whilst messing around too.

[exxos]

As Phil said, do the DMA and 1772 mods..

https://www.exxosforum.co.uk/forum/viewt ... =17&t=1395

https://www.exxosforum.co.uk/forum/viewt ... =17&t=1417

But also I can pretty much guarantee, that those RAM upgrades with long cables are not going to help with any sort of accelerator.

And why have you got "F" series chips in there ? even stock machines struggle to run with those chips, I have documented this many many times over the years. You should basically never use anything on the ST's other than LS series. The faster rise times and higher current capabilities of the F series are likely going to compound the problems with the long cables you have on that RAM upgrade making the thing even more unstable.

If that is an image of your machine, you should not be using parity Simms with accelerators, or at all in actual fact.

so I would suggest you do the mods first, and look at removing that RAM upgrade and trying things again.

[TheNameOfTheGame]

Thanks guys. I will read the threads exxos linked.

As for the drivers, I was going by this paragraph in the PAK manual. Also another user over at atari-forum whose system was freezing with the PAK changed his 373 chips and the freezing stopped.

manual_pak_drivers.png (66.78 KiB) Viewed 4920 times

[PhilC]

Mine has the stock LS's fitted to all 4 chips.

[exxos]

The point about ACT types, yes, but its also for F series as well. "Bus terminators" well no, they are pull-ups. Generally I have found 2.2K is needed for address and databus. Swapping buffer chips is not a good method. Stick to LS types.

As said before, those marpets are basically junk. I've had machines here with marpets in before with people trying to install my boosters, I just gave up in the end. I'm not trying to sell you my RAM kit, but all my boosters worked fine with my own 4MB RAM boards.

60ns might not be stable either. some machines get away with it if you use 33R resistors in the lines. Most STF's use 47 & 68. Thats very "hit and miss" for 60ns RAM.. Long cables and parity simms are just going to aggravate the issues along with 60ns RAM.

[TheNameOfTheGame]

Hmm, that's making me think. Thanks for the suggestions.

Regarding the discussion on RAM timings. Just to clarify, the system seems stable. I would think RAM timings issues would result in crashes/freezes/etc. So you're considering that RAM timing issues could manifest in DMA/Floppy issues alone and the rest of the system would be stable?

*Edit* Also from the PAK manual:

manual_pak_ram.png (34 KiB) Viewed 4910 times

[exxos]

Regarding the discussion on RAM timings. Just to clarify, the system seems stable. I would think RAM timings issues would result in crashes/freezes/etc. So you're considering that RAM timing issues could manifest in DMA/Floppy issues alone and the rest of the system would be stable?

RAM can cause the entire bus to become unstable, again this is aggravated with F series buffers, and long cables. The RAM itself could perfectly be fine, and you can even run ram test all day without issues, but this is the entire "DMA" type issue which is always there on the STE. its " combinational factors" which cause bores on sustainability, it is not just so simple as being one individual item.