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Can I use one of my myarc hfdc just as a disk controller with no hard drive attached? Seems to me I remember having to add a switch or something to be able to do this?

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Where is U21? I can only find M21 on the schematics.

 

(Beside the fact that someone should redraw those schematics ...)

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I actually did an image search on google with ti-99/4a hfdc and found an image that was large enough for my tired old eyes to see. It's on the left side.

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Oh, I did not even remember that I once put a photograph on ninerpedia: http://www.ninerpedia.org/index.php/Floppy_Disk_and_Hard_Disk_Controller_Cards

 

U21 is one of the two CRU read interface chips; the schematics hints at a ground connection on that pin. That is, if pin 1 is grounded this should have an effect when reading that CRU bit (e.g. by TB 3), but it has no effect on the other circuits on the controller. So this seems to me like an undocumented feature in the DSR.

 

Interesting - maybe I should add that switch to the MESS emulation as well.

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Oh, I did not even remember that I once put a photograph on ninerpedia: http://www.ninerpedia.org/index.php/Floppy_Disk_and_Hard_Disk_Controller_Cards

 

U21 is one of the two CRU read interface chips; the schematics hints at a ground connection on that pin. That is, if pin 1 is grounded this should have an effect when reading that CRU bit (e.g. by TB 3), but it has no effect on the other circuits on the controller. So this seems to me like an undocumented feature in the DSR.

 

Interesting - maybe I should add that switch to the MESS emulation as well.

 

Here is the corresponding EPROM Code from SECTORIOx. You can reduce the delay by modifying the loop counter or eliminate the test altogether with the hardware mod.

 

 

WATDR1 EQU  3            IF "1" THEN WAIT FOR READY, IF "0" THEN DON'T WAIT
 
* NOW TEST TO SEE IF THE DRIVE IS READY ONLY DO THIS FOR DRIVE 1
       C    @VOLUME,@H0001
       JNE  DRVRDY
       ABS  @WAITD1
       JNE  DRVRDY
       SETO @WAITD1              MAKE IT NON ZERO
       TB   WATDR1            TEST IF WE SHOULD WAIT FOR DRIVE 1 TO BE READY
       JNE  DRVRDY            IF 1 THEN WAIT, IF 0 THEN GO ON
 
       LI   R5,75
WTRDY  BL   @SETDRV           USES R0 AND R2 MUST BE SET
       BL   @READR9           USES R0   TEST READY
       SLA  R0,3
       JNC  WTRDY2            THE DRIVE SAID IT WAS NOT READY
       BL   @READR9
       SLA  R0,3                         TEST READY
       JOC  DRVRDY            READY TWICE IN A ROW
WTRDY2 MOVB @CBH01,@CMDREG
       BL   @WTCD10
WTRDY1 DEC  R0
       JNE  WTRDY1
       DEC  R5
       JNE  WTRDY
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Again the HFCD. It seems very popular. Are there any other mod’s for that controller? (besides those two on whtech?) Does it take any “old” PC 5.25” and/or 3.5”, DD or HD drive, or does work best with a particular drive?

I’m not sure where to look for that kind of information.

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ah, OK. But is there any advantage to disable the floppy-controller (as it supports 80tracks...) ?

What could be the reason for HDD-use only ? Act as 2nd HDD-controller ?

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You can make it act ONLY as a hard drive controller with a modified EPROM.

 

From the HFDC manual, page 7:

 

Note – by adding a floppy controller in addition to the HFDC, you can control up to 8 floppy drives. With two controllers the HFDC controls drives 5 through 8. Set up the physical drives that will be used as drives 5 through 8 as if they are drives 1 through 4, cabling them to the HFDC. The HFDC will address them as if they were the higher numbers.

 

If I understood that correctly, it says you can use a separate disk controller for your floppy drives, and only hard drives with the HFDC.

 

 

One reason could be that some people experienced stability issues with the HFDC and their floppies, or they simply wanted to continue using the disk controller they got used to.

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^^^^^^^^ that is correct, I have done it when I had one of my gennys set up. A corcomp controller was used for drives 1-4 and I had 2 80 track drives hooked up to my hfdc. I don't remember any issues.

Ralph.

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I have a BWG Disk Controller for DSK1-3 and RAMdisks from DSK4-D. When I was using a HFDC, it was used as a Hard Disk controller ONLY - it will support two in R/W mode and a third read-only. The EPROM is a direct substitution for the original and just eliminates floppy drive access (courtesy: The Great Gazoo).

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