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.