Whoops. Almost royally screwed up. Got to make a design change.
These are 2MB chips. the on-board RAM is only 1 MB in size, and the decoding to external address space starts at 2MB. Problem is, the New RAM is 20 bits in size, while the original is a total of 19 bits in size. So, if I leave A19 of the toshiba RAM hooked into A20 of the original addressing space, that would kill off the first 1MB on my toshiba chip, basically wasting half the chip, as A20 would be high when moving into external addressing. Since A20 is routed to the toshiba chips, well yea....
So, I am going to have to break off A20 from the RAM. Leaving the RAM only accessing in 1MB chunks. Then, move A20 to the CPLD and do some 1-2 decoding to use the full address space.
Wow... good thing I caught that. Doing the CPLD work is what made me think of this.
This is precisely the reason that when using memory modules in computers, they all have to be "equal"
Elfin: Even if I did copyright it, whos got the money to hire a bunch of lawyers and court proceedings to fight an infringement? I dont, so who cares? Plus this is strictly a niche market with a small yield so it doesnt really matter.
These are 2MB chips. the on-board RAM is only 1 MB in size, and the decoding to external address space starts at 2MB. Problem is, the New RAM is 20 bits in size, while the original is a total of 19 bits in size. So, if I leave A19 of the toshiba RAM hooked into A20 of the original addressing space, that would kill off the first 1MB on my toshiba chip, basically wasting half the chip, as A20 would be high when moving into external addressing. Since A20 is routed to the toshiba chips, well yea....
So, I am going to have to break off A20 from the RAM. Leaving the RAM only accessing in 1MB chunks. Then, move A20 to the CPLD and do some 1-2 decoding to use the full address space.
Wow... good thing I caught that. Doing the CPLD work is what made me think of this.
This is precisely the reason that when using memory modules in computers, they all have to be "equal"
Elfin: Even if I did copyright it, whos got the money to hire a bunch of lawyers and court proceedings to fight an infringement? I dont, so who cares? Plus this is strictly a niche market with a small yield so it doesnt really matter.