Practical Peripherals Microbuffer II ROM Dumps?

Is that card supposed to work with two of the RAM chips missing?  Possible I guess.

I'd suspect one of the 74LS374s, the 74LS39 and the 74LS139 in that order.  Lucky those are all cheap and easy to get parts.

I would thing that bad ROMs on a card like that wouldn't normally cause the computer to fail to boot.  Even without a known good image to compare to, if you can read the EPROMs out, you can look at the contents and see if it looks like valid 6502 code.  Usually when EPROMs go bad they will read out as all zeros or all ones or repeated alternating patterns or occasionally random-ish garbage.  The chip marked EPSON may contain data like tables of codes, so it may not all be 6502 code.  I don't know for sure because I never had this particular card myself.

Yet not tested, but the Strings inside seem to be correct:

http://www.ralf-kiefer.de/A2/PracticalPeripherals/1802_Firmware.BIN

http://www.ralf-kiefer.de/A2/PracticalPeripherals/1802_SlotROM.BIN

Regards

Ralf

softwarejanitor wrote:

I'd suspect one of the 74LS374s, the 74LS39 and the 74LS139 in that order.

I would try to fix it exactly this way.

The EPROM marked with "EPSON" must be 6502 code, the other EPROM ("MB2-A") holds the RCA1802 code.

Does anybody have a User Manual or something like that?

Regards

Ralf

RalfK wrote:

softwarejanitor wrote:

I'd suspect one of the 74LS374s, the 74LS39 and the 74LS139 in that order.

 

I would try to fix it exactly this way.

The EPROM marked with "EPSON" must be 6502 code, the other EPROM ("MB2-A") holds the RCA1802 code.

 

Does anybody have a User Manual or something like that?

This looks like it:

http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Parallel/Practical%20Peripherals%20Microbuffer%20II/Manuals/

softwarejanitor wrote:

Is that card supposed to work with two of the RAM chips missing?  Possible I guess.

Yes, all the print buffers I know of used 64Kbit DRAM chips singly or in 16KB pairs:

• Orange Micro Bufferboard: 16KB (2 DRAMs), 32KB (4 DRAMs), 64KB (8 DRAMs)
• Wesper Micro "Wizard S.O.B." serial output buffer: 16KB (2 DRAMs), 32KB (4 DRAMs)
• Buffered Grappler: 16KB (2 DRAMs), 32KB (4 DRAMs), 64KB (8 DRAMs)
• MicroTek Dumpling-64: 8KB (1 DRAM), 16KB (2 DRAMs), 32KB (4 DRAMs), 64KB (8 DRAMs)
• Practical Peripherals Microbuffer II: 16KB (2 DRAMs), 32KB (4 DRAMs)
• Perisoft Bufferlink: 8KB (1 DRAM), 16KB (2 DRAMs), 32KB (4 DRAMs), 64KB (8 DRAMs)

But I'm not sure why Wesper thought "S.O.B." was good branding...

S.Elliott wrote:

softwarejanitor wrote:

Is that card supposed to work with two of the RAM chips missing?  Possible I guess.

Yes, all the print buffers I know of used 64Kbit DRAM chips singly or in 16KB pairs:

• Orange Micro Bufferboard: 16KB (2 DRAMs), 32KB (4 DRAMs), 64KB (8 DRAMs)
• Wesper Micro "Wizard S.O.B." serial output buffer:

Fair enough.  I just don't remember ever seeing a card like that which wasn't fully populated.  And all the other pics I found online googling it had all the sockets filled, although a couple had different brands of chips in the two banks, which fits with it having been originally sold as a 16k card that someone upgraded later.

One of the other brands which was a long card that used 4116 type RAMs I remember seeing only one of the two rows of 8 populated.  They were older than this card, the 4164 chips probably weren't available or were more expensive back then.  I can't remember what card that was but a friend of mine had one back in the day.  If I remember right it had both serial and parallel options or there were two versions of the card, I don't remember exactly now, but if I recall there were two sets of connectors.  That was around 40 years ago.  And my memory while not as bad as an MT DRAM chip ain't what it used to be.

There were a lot of companies that had unusual ideas about marketing in the 1970s and 1980s.  It was a different era and a lot of the people involved in the early microcomputer days were...  uhhh... Quirky?  Even by computer geek/nerd standards.  So some really pretty weird people with non socially conforming senses of humor.  Not that there is anything wrong with that.  Those were more interesting times with all that implies.

VeryVon wrote:

Hello all and thanks for your input!!  This gives me much more confidence to move forward troubleshooting this card.  I'll start looking into the 74LS chips mentioned and see if I have spares etc.

About the RAM chip population, per the users manual SW5 controls 32k or 16k buffer (4/2 RAM chips populated) and SW6 enables or disables the buffer.  I did try disabling the buffe

The reason I suggested the chips I did is because they are usually related to the address decoding and data bus logic, and I agree that is what your card sounds like it is doing.