I purchased a pc enterprises 192k internal memory board. I installed it and the pcjr beeps twice and won't start (it will if I remove the card.)
I noticed that the card has a jumper on it. Should I change the jumper configuration. Thank you
pcjr has Tecmar captain and cadet attached.
pc enterprises 192k internal memory board
Re: pc enterprises 192k internal memory board
Yep, I think you're going to have a problem ...
The internal memory slot can't handle 192KB by itself - it doesn't have enough address lines. The standard card is just 64KB. Adding one address line would have brought the card up to 128KB. They must have added two address lines, which could have brought the card up to 256KB. I'm not sure why they stopped, other than maybe there is an interleaving issue with the 64K of memory on the motherboard. (It's possible that 64KB on the card is interleaved, and the other 128KB is not.)
Anyway, I've never seen one but I'm quite sure it requires an extra two (or more) wires to the motherboard to pick up the extra address lines. If the person who sold you the card did not include instructions you are going to have to reverse engineer the card. If you post some high resolution pictures of it we might be able to figure it out. (We'll need to see the chips used and any spots for wires that might attach to the motherboard.)
I'm hoping a lurker out there has one of these in their system and can take pictures or describe how the extra connections are made. You might be able to find somebody at PC Enterprises who has the old documentation, but that is a really long shot.
The internal memory slot can't handle 192KB by itself - it doesn't have enough address lines. The standard card is just 64KB. Adding one address line would have brought the card up to 128KB. They must have added two address lines, which could have brought the card up to 256KB. I'm not sure why they stopped, other than maybe there is an interleaving issue with the 64K of memory on the motherboard. (It's possible that 64KB on the card is interleaved, and the other 128KB is not.)
Anyway, I've never seen one but I'm quite sure it requires an extra two (or more) wires to the motherboard to pick up the extra address lines. If the person who sold you the card did not include instructions you are going to have to reverse engineer the card. If you post some high resolution pictures of it we might be able to figure it out. (We'll need to see the chips used and any spots for wires that might attach to the motherboard.)
I'm hoping a lurker out there has one of these in their system and can take pictures or describe how the extra connections are made. You might be able to find somebody at PC Enterprises who has the old documentation, but that is a really long shot.
Re: pc enterprises 192k internal memory board
I kind of figured when I saw the card in person that it probably wasn't going to work. Thanks for your response Mike.
Here is a picture of the 192k card.
Here is a picture of the 192k card.
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- 192k card.jpg
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Re: pc enterprises 192k internal memory board
Well, that is definitely a 192KB card. I did a double take when I saw only six DRAM chips. Normally something that old uses 64Kx1 bit or 256Kx1 bit chips. Those chips are 64Kx4, so two chips make a 64K bank.
I never truly realized the beauty of the internal memory card before. Besides being able to decode the CPU address bus, it also can access the memory using the lower level Column Access Strobe and Row Access Strobe. The block diagram in the tech ref is making my eyeballs bleed.
If I were designing this card I would keep the lower 64KB exactly the same as on the original card; that 64KB needs to be accessed by both the CPU and video memory. But the next 128KB are only accessed using the CPU bus. The card already has 8 data lines, 8 address lines, and some support lines like write enable. To access another 128KB you would need just a few more pins. It'd be awesome to find a picture of an existing installed setup to see what parts of the motherboard they tapped to get the address lines for the next 128KB.
I never truly realized the beauty of the internal memory card before. Besides being able to decode the CPU address bus, it also can access the memory using the lower level Column Access Strobe and Row Access Strobe. The block diagram in the tech ref is making my eyeballs bleed.
If I were designing this card I would keep the lower 64KB exactly the same as on the original card; that 64KB needs to be accessed by both the CPU and video memory. But the next 128KB are only accessed using the CPU bus. The card already has 8 data lines, 8 address lines, and some support lines like write enable. To access another 128KB you would need just a few more pins. It'd be awesome to find a picture of an existing installed setup to see what parts of the motherboard they tapped to get the address lines for the next 128KB.