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Myarc 512k, CRU and DSR craziness


OLD CS1
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I really like my Myarc 512k card. It has a few quirks about which I have harbor no disdain; in particular that I will probably never use the print spooler so that is 80k I can never use and a max 400k RAM disk. Beyond that, tonight I have stumbled across more than just a quirk but rather a real compatibility annoyance.

In my system I have the Myarc 512k, TI RS-232/PIO, WHT SCSI, and BwG DSDD floppy cards. First I found CFHDX would consistently lock up. Then that the only floppy manager I could use to format disks is the TI Disk Manager. Then another weird thing, CALL PART (to provision the Myarc 512k) and a few other sub-programs would crash Extended BASIC 2.7. Somewhere along the line I found that Myarc Disk Manager 5, DM1K, DM2K, and CFHDX in XB2.7 Suite would crash when trying to access SCS2 (Myarc DM5 corrupts and crashes immediately.)

Replacing the Myarc 512k with the TI 32k is the fix to all of the above.

A listing of available DSRs in DM2K gives:

 

post-27864-0-25351300-1433584335_thumb.pngpost-27864-0-67672600-1433584329_thumb.png

 

The Myarc populates >1000 and >1900, the BwG at >1100, TI RS232/PIO at >1300, and the WHT SCSI as >1700.

 

As well, the Myarc exports the DSK, DSK1, etc. DSRs at >1000. When trying to format a floppy using the advanced disk management programs, even with DSK emulation explicitly disabled using CALL EMDK(0). The programs find DSK1 at >1000 and all hell breaks loose. This explains the problem with floppies.

 

I have no clue what causes the crash when accessing SCS2 with the Myarc 512k installed.

 

With the BwG and the Myarc 512k both hard-wired at >1100 and >1000, respectively, I do not see a way around the DSK issue. If I could put the BwG first, then using the on-board DIP switches I could configure it to pass anything beyond DSK1 to another card, such as the Myarc 512k with DSK2 emulation via CALL EMDK(2). Of course, this eliminates my ability to LOAD from the Myarc RAM disk configured as DSK1.

 

Of course, even if I can correct the DSK issue, I am still left with the unresolved lock-ups accessing SCS.

 

The above is mostly just to document my observations for posterity.

 

Now I will pose a question: since I have purposes for the Myarc 512k and I also wish to maintain general compatibility, what I would like to do is have a switch that allows me to select between the Myarc 512k and the TI 32k card, thus preventing me from having to swap cards depending upon my task. Does anyone have thoughts on the difficulty or logistics of such a switch?

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Have you tried removing the Eprom on the card? If doing so resolves the problems, a switch could be installed to enable/disable the DSR.

 

Gazoo

 

Nope, but I will give it a shot. How would I disable the TI 32k? The two cannot coincide.

 

EDIT: Never mind... if the DSR exporting DSK{x} is the problem, then in theory simply disabling the DSR should be enough... no TI 32k needed.

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Nope, but I will give it a shot. How would I disable the TI 32k? The two cannot coincide.

 

EDIT: Never mind... if the DSR exporting DSK{x} is the problem, then in theory simply disabling the DSR should be enough... no TI 32k needed.

 

Correct. If you find that solves the troubles, you can probably connect a switch to connect/disconnect the chip enable pin (20). Bend the pin out, solder a wire to it, solder another wire to the socket pin 20 pad on the bottom of the board, and connect the 2 wires to an spst switch.

 

Gazoo

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No joy. Removing the DSR ROM makes the disk managers work properly but accessing the SCSI card still crashes. The SCSI LED illuminates and all other LEDs extinguish.

 

I am going to change the CRU address of the SCSI card to see if that helps. Right now it is at >1700. Maybe if I move it to >1200.

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Any access to the SCSI drive with the Myarc in results in lock-up, even from BASIC/XB. I can find the MDM5 disk and try it, though.

 

Even with DM2K?

 

If so, stop playing with the eprom. :) Just put it back in.

 

I wonder if a card can be shutdown just by disabling the '245?

 

If so you could run 2 wires from each of the memory cards and attach them to a DPDT switch like so:

gallery_29515_833_3662.jpg

And just to confirm, MDM5 works ok loaded from the XB v2.7 Suite cart with the 32k card in place. You can access the SCSI drive with it?

 

Gazoo

Edited by Gazoo
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Correct. With the TI 32k card, MDM5 and the other disk utilities on the XB 2.7 Suite cartridge work properly. It is only with the Myarc 512k card in place that MDM5 crashes, and everything else locks up as soon as SCS2 is touched.

 

I really like the RAM disk, but I am beginning to wonder whether it is worth the hassle. I am probably just saying that because I am tired, in pain, and drugged up right now :) I will look into a little mechanism to implement your idea. Sadly, it will not be any time soon as I have run out of time to play with this particular part of the project.

 

Thanks for the help and idea. I will be back!

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