will it compute? btl's attempt to build the H4

[PaulJ]

Icky, everything that the Atari diagcart can test is working. That includes the test's you need the atari test board for, dma, parallel, midi, seial, and joystick ports. :) :) :) Haven't tried floppy external port or two floppies.

[exxos]

The internal drive should work with a original 720K drive and a PC drive (unmodded) same with the external one.

[btl]

I tried to use two Epson SMD-380 (ST 720k drives) on the H4:

both work when the only drive, no matter if jumpered ID0 or ID1
as soon both are connected, no access to disk possible

jumpers are set as in build guide.

[exxos]

Do the select lines on the drives make any odds when both drives connected ?

[btl]

You write of the ID select jumpers?

If so, no, with a straight cable no difference, but now i found a flipped cable (PC style)
Now i get a bit different experience Drive A (straight connected, ID0 jumpered) works, as
long no disk is inserted to drive B (flipped connected, jumpered D1 (tried D0, too))

I'm open for hints, even if super obvious, shoot!

[exxos]

How do you have the AB swap jumpers set up ?

[btl]

Code: Select all

    3 2 1 
    o-o o
    o o-o

[exxos]

That should be fine.. I don't really know of any reason why a external drive would cause the internal one to malfunction Unless you have a bad joint on the signals back to the sound chip or something.

[btl]

My 2nd drive is not on the rear port, i connected both on the same internal cable. Should work, too?

[exxos]

My 2nd drive is not on the rear port, i connected both on the same internal cable. Should work, too?

No.. I never thought anyone would use 2 drives on the internal cable. I don't even know if that even works on a normal STFM ? Don't think I ever saw anyone even trying it.