John Coffman
2015-10-10 17:06:15 UTC
Todd has been sold-out of the SBC-188 (rev. 2) board for some time now,
and I did not know whether interest in the board had waned or whether a
re-spin was in order.
AFAIK, the present board has only one issue, a clearance problem in
mounting a SuperCap to the board. To fix this issue, a new drill mask
would be needed, and this incurs the full engineering charge by the
manufacturer. So if this issue is addressed, it might be time to
consider several other updates:
1. Address the SuperCap clearance issue.
2. Technical change to memory selection: use /A19 to select low
512K memory, freeing up the Middle Select to allow programming wait
states for the VGA and 4MEM address ranges. Low Select still unused; no
change to High Select for ROM.
3. Change UART to PLCC to save space.
4. Change MAX232 to 233 to eliminate caps, possible space saving.
5. Change DTR/DSR output to RTS/CTS. PLCC -550C UART can do latter
in h/w.
6. Add an IDE connector in one of two ways:
a. Change PIO 26-pin connector to PPIDE 40-pin connector at
board edge.
b. Eliminate 8255 completely, and go to 8-bit IDE interface
like the Mark IV.
Does anyone use the 8255 for anything other than PPIDE through a
daughter board?
7. Change interrupt connection so /INT better supports the keyboard
on the CVDU or (future) VGA board.
The SBC-188 is a very dense board; changes that use less board space are
easy; changes that use more board space may not be possible.
Any comments or further ideas would be appreciated.
--John
and I did not know whether interest in the board had waned or whether a
re-spin was in order.
AFAIK, the present board has only one issue, a clearance problem in
mounting a SuperCap to the board. To fix this issue, a new drill mask
would be needed, and this incurs the full engineering charge by the
manufacturer. So if this issue is addressed, it might be time to
consider several other updates:
1. Address the SuperCap clearance issue.
2. Technical change to memory selection: use /A19 to select low
512K memory, freeing up the Middle Select to allow programming wait
states for the VGA and 4MEM address ranges. Low Select still unused; no
change to High Select for ROM.
3. Change UART to PLCC to save space.
4. Change MAX232 to 233 to eliminate caps, possible space saving.
5. Change DTR/DSR output to RTS/CTS. PLCC -550C UART can do latter
in h/w.
6. Add an IDE connector in one of two ways:
a. Change PIO 26-pin connector to PPIDE 40-pin connector at
board edge.
b. Eliminate 8255 completely, and go to 8-bit IDE interface
like the Mark IV.
Does anyone use the 8255 for anything other than PPIDE through a
daughter board?
7. Change interrupt connection so /INT better supports the keyboard
on the CVDU or (future) VGA board.
The SBC-188 is a very dense board; changes that use less board space are
easy; changes that use more board space may not be possible.
Any comments or further ideas would be appreciated.
--John
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