I think we are very close to have all boards updated to be able to create a reliable replicas of the H8 system. There is a new standalone H17 in the works that supports USB/2.5” floppy drives. I’m planning to have a new full size memory board that will support 512KB and it should work with all the Z80/8080A monitors along with the ORG0 circuit. I want to have all new boards full size to secure better the boards within the chassis.
For the H8 extender board, I have in mind an H89 debug board to fix and operate the H89 boards on the H8 chassis, such as the serial port and disk controllers.
This is in the works:
Thanks,
Norberto
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Rick: how did you get to boot without floppy? That seemed like the hard part? Since you want to run on an 8080 you can’t use PAM-37 or Magnolia ROMs? So did you add a boot capability to the XCON-8 ROM?? As I understand it, the reason we’ve centered on the Z67IDE approach is because that’s what Heath and Magnolia baked into their ROMs…
You’ve done an amazing job on this board!
If I understand correctly the advantages to this board (vs. say the Z67-IDE+ approach) are (please correct me if I'm wrong):
Douglas might be able to help with CP/M3 support if he had the information needed for his emulator…
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Norberto: thanks for the update. What’s the difference between #1 and #3 in your list? Aren’t these both “Rick’s” CF board?
Has the H8-Z5-4 Serial Console & Cassette IO V1.0 been released yet? I don’t see it on Todd’s list yet so perhaps the ball is in his court?
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What’s the difference between #1 and #3 in your list?
#1 connects to the Heath H67 controller. Attached is a picture:

It is an update from the original Z67-IDE board that only runs at 4Mhz. I had to rework the board to get 16 bit communications as 8 bit setup failed.
The board is fully functional, just that the CF cards needs to be reconfigured for 16 bit transfers. It can be inside the H8 chassis or outside on its own chassis.
Thanks,
Norberto
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I thought the new CF boards were going to be direct-connect to be simpler (more like the GIDE but even simpler). Has that plan changed?
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Douglas,
I was not able to get the 8 bit setup to work. I had to go back to original design with the 8255 IC.
Norberto
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On the H89, the possible address are:
174Q, 274Q, 170Q, 274Q. The serial I/O ports cannot be used. For this board 270Q and 274Q could be used.
Norberto
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This was on the Z67-IDE? Or are you saying that the H8 bus
control signals do not meet the timing (we haven't got the timing
right yet)? It should be possible to directly connect the to CF,
that is done on other platforms, even at faster CPU speeds.
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You have a point as it was on the Z67-IDE board. Attached are the schematics and simplified board.
Check them out to be correct as this has to work to avoid overhead in debugging such board.
Norberto
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I look forward to trying this board out once it’s available. Perhaps install it in my original 8080-based H8 system from Way Back When, which I’ve kept pretty pristine all these years…
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This looks about what I'd expect.
Some general questions, though, about the data bus buffer(s).
First, I see you have two data bus buffers and I'm wondering why.
Second, the first DB buffer (connected to the H8 bus) is driven by
WR, while the second (and the CPU board's buffer) is driven by RD.
I believe the correct way to do this is by RD, as that preserves
the CPU's write hold time for data. Otherwise, you risk race
conditions on latching the data at the peripheral chip (CF). I'm
thinking that two DB buffers makes this worse, especially with one
triggered off RD and the other off WR. Not to mention the extra
propagation delays through the second set of buffers.
Looking at the original H8 8080 CPU board, it appears that the CPU DB buffer is driven off RD (which I believe is correct). I can't tell what the Z80 v4 board does.
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Both Data buffers are driven by the RD signal. U10A pin 4 “SSI-DIR” is a combination of “BRD_SEL + BRDL”. The “BWRL” on pin 1 of U10A is not doing anything at all as the state is driving by the “B02” signal. I can eliminate U2 buffer, but I think the CF card bus cannot be expanded by adding an IDE cable.
Let me know if I should eliminate U2. I will delete BWRL pin 1 of U10A as it is not doing anything.
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Rick,
Is the .H8T file included in the H8D image? How I get CP/M to work with this board? Any instructions?
I will continue to work with Douglas on the Simplified version of this board to boot with CP/M3. Once the simplified board is working, then I will need your help to get it working with HDOS2/3 and Heath CP/M.
Thanks for all your help and updated website with the attached file.
Norberto
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Thanks and added to webserver. 😊
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I can't fully tell when the enable pin on U2 is active, so am
still not sure of the timing. Does the 74HC245 have different
drive capabilities than the 74HCT640? Is there something else on
the Dx+ lines besides U2? Otherwise, it seems unnecessary to me.
As long as the timing is such that /WR data remains active after
/WR goes inactive, I guess it should be OK.
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FYI, there is a boot module in the new (Z80 V4) ROM for the
simplified CF interface. That should allow booting any OS
directly, provided the CF image is created correctly (bootstrap
sectors exist). I'm not sure how Richard has setup these images,
it would be nice if they were compatible with standard Heath
bootstrapping - i.e. the H8T file essentially does a standard
Heath boot.
Norberto, you spoke of a new 8080 CPU board with expanded ROM
capabilities? That will require a port of the ROM code to
eliminate Z80 instructions (and Z80 register handling), which is
not trivial but is doable.
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This is where a “roadmap” of these storage options would be handy.
I thought the primary purpose of Rick’s dual-CF board was to support the 8080 community? I guess for completeness we could add a boot capability for his board to the Z80 V4 but sticking to a Z67 centric approach (e.g. the Z67-IDE+, and new derivatives thereof that Norberto is working on) makes more sense to me since it’s already supported in the PAM-37 ROM and other ROM enhancements from Douglas and Terry G.
It would seem that any “new and enhanced” 8080 CPU board (e.g. the one Norberto referred to in his email today) should have some kind of hard drive (i.e. SSD) boot support, presumably using Rick’s (already developed) boot code for his dual CF board? I guess the other approach that was discussed here was the one used for GIDE implementations? Don’t know much about that… (I think Terry G is the expert? This goes back to Les’ original Z80 clone board, which included GIDE support)
Adding Z67 support to the 8080 world (e.g. ROMs) would seem like a difficult (and ill advised) path…
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I don't believe there is anything about either CF solution that
requires or is restricted to the 8080 CPU. If a board works on the
H8 bus, the hardware should work with any CPU (just like the Z80
CPU boards work with existing peripheral boards). Then it's just a
matter of software/ROM support. If a new 8080 board has an
expanded ROM, then we can add many more capabilities. Rick's H8T
boot solution is a way of providing new boot capability to the
smaller ROM systems.
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Is there a need to be using IDE connectors plus the IDE-CF adapters? There are thru-hole CF sockets available and from what I hear the IDE-CF adapters can be flaky, or at least the quality can be inferior depending on the make. Is there really a need to support actual IDE-connected rotation drives? If not, perhaps this should be eliminated.
I had wanted to have the direct-connect CF board to be laid out for thru-hole CF sockets. The schematic does not show that, but maybe there is time to change that.
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