daver2
10k Member
This is the best photograph of the top of the buffer board I have been able to find:
https://www.worthpoint.com/worthopedia/rockwell-aim-65-early-computer-buffer-2001589385
1 * 245 (data bus buffer) and 2 * 244 (address buffers).
C2, C3 and C4 must be decoupling capacitors for the TTL ICs.
I guess C1 is across the +5V power supply?
Not sure what the single resistor does - or what the 3 resistor packs do yet...
I see a link as well - possibly to isolate the +5V supply from the Aim-65 to the expansion bus?
The schematic etc. is in here http://retro.hansotten.nl/uploads/files/1984 Rockwell databook ch9 RM65.pdf on page 9-88. The only thing missing now is the PCB layout...
Although I have noticed that the TTL part numbers are different between the schematic and photograph - and the photograph has a discrete resistor that does not appear in the schematic.
CORRECTION: The discrete resistor is on the schematic! Just found it...
It looks like the difference between the photographs and schematic device IDs is that the 245/244 are non-inverting whilst the 640/240 are inverting. It looks like from the connector pinouts that the AIM-65 as an active high address/data bus whilst the RM65 is an active low address/data bus - so the inverting variants should be the ones to use for consistency...
Dave
https://www.worthpoint.com/worthopedia/rockwell-aim-65-early-computer-buffer-2001589385
1 * 245 (data bus buffer) and 2 * 244 (address buffers).
C2, C3 and C4 must be decoupling capacitors for the TTL ICs.
I guess C1 is across the +5V power supply?
Not sure what the single resistor does - or what the 3 resistor packs do yet...
I see a link as well - possibly to isolate the +5V supply from the Aim-65 to the expansion bus?
The schematic etc. is in here http://retro.hansotten.nl/uploads/files/1984 Rockwell databook ch9 RM65.pdf on page 9-88. The only thing missing now is the PCB layout...
Although I have noticed that the TTL part numbers are different between the schematic and photograph - and the photograph has a discrete resistor that does not appear in the schematic.
CORRECTION: The discrete resistor is on the schematic! Just found it...
It looks like the difference between the photographs and schematic device IDs is that the 245/244 are non-inverting whilst the 640/240 are inverting. It looks like from the connector pinouts that the AIM-65 as an active high address/data bus whilst the RM65 is an active low address/data bus - so the inverting variants should be the ones to use for consistency...
Dave
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