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Designing a portable RAM card
- Thread starter techknight
- Start date
techknight
Well-known member
Replacing the RAM IC fixed it. So out of a handful from trag, only one was bad. Turns out I did not need DTACK so ill omit that in the next PCB revision.
Thats pretty good.
BTW. I only ordered 5 PCBs to make sure it all worked. First come first served.
Your looking at $75 per board for one without the LEDs. Or $80 if you want the LEDs for the cool factor.
I need to know how many are interested and qty so I can order all the correct parts.
Thats pretty good.
BTW. I only ordered 5 PCBs to make sure it all worked. First come first served.
Your looking at $75 per board for one without the LEDs. Or $80 if you want the LEDs for the cool factor.
I need to know how many are interested and qty so I can order all the correct parts.
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techknight
Well-known member
Ok. I started a new thread in the trading post for pricing and orders.
Hmmm. That's a 1 out of 9 failure rate on the chips so far. That's not so good. I hope you just happened across the bad apple and that's not typical.
Have you tried running something like NewerTech's RAMometer memory test (also available in Guages) or some of the memory tests in TechToolPro? Check the chips bitwise...
Fabulously excellent work.
Hmmm, browsed the thread again, rereading your progress.
I also suggest you test RAM performance (RAMometer will give you a MB/S tested indicator) with and without your DTACK wire connected. Is it possible that without DTACK, the CPU is timing out and assuming the data is on the bus at some point, but that with DTACK, the transaction might complete several cycles sooner?
If there's some logical reason why the above paragraph is misdirected, feel free to ignore it.
Have you tried running something like NewerTech's RAMometer memory test (also available in Guages) or some of the memory tests in TechToolPro? Check the chips bitwise...
Fabulously excellent work.
Hmmm, browsed the thread again, rereading your progress.
I also suggest you test RAM performance (RAMometer will give you a MB/S tested indicator) with and without your DTACK wire connected. Is it possible that without DTACK, the CPU is timing out and assuming the data is on the bus at some point, but that with DTACK, the transaction might complete several cycles sooner?
If there's some logical reason why the above paragraph is misdirected, feel free to ignore it.
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techknight
Well-known member
DTACK is generated automatically by the GLU. So i dont need to worry about it. The backlit portable has no wait states. So the speed is literally as fast as the RAM access time.
The non-backlit has wait states, I present the data available instantly, but the machine can only accept it within a certain amount of wait-states.
Its hard to say why the chip was bad. I could have killed it for all i know. I dont have any ESD matting or anything.
Also, do you have a link to any of those utilities?
The non-backlit has wait states, I present the data available instantly, but the machine can only accept it within a certain amount of wait-states.
Its hard to say why the chip was bad. I could have killed it for all i know. I dont have any ESD matting or anything.
Also, do you have a link to any of those utilities?
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techknight
Well-known member
Now thats odd.
I got 9MB on haplains board, at the shop with my portable HDD.
Since I dont have an HDD solution yet on my non-backlit portable at home, I am booting off a 6.0.7 disk tools disk. Well same thing. Memory manager error and address error when using 9MB....
Do you have to have a full install of 6.0.7? or a system enabler I am not aware of?
I got 9MB on haplains board, at the shop with my portable HDD.
Since I dont have an HDD solution yet on my non-backlit portable at home, I am booting off a 6.0.7 disk tools disk. Well same thing. Memory manager error and address error when using 9MB....
Do you have to have a full install of 6.0.7? or a system enabler I am not aware of?
eraser
Well-known member
The Mac LC should be your inspiration because this is exactly what Apple did with it: The LC has a 16-bit bus and it's running a '020.
On the PC side of the fence Intel released the 386SX which was the low cost version of the 386DX. The 386DX had a full 32-bit external bus and the 386SX had a 16-bit external bus and fewer pins. The actual core of the two chips were effectively the same. (In the 1980s and early 1990s it was a lot more expensive to make a 32-bit system because your bus had to have many more traces.) I know that for Intel, they solved the problem by using 2 clock cycles to load a complete instruction. That is, every other clock cycle would either be the "high 16" or the "low 16."
Since the '020 doesn't have a shorter bus variant I do wonder how Apple made it work. At least we know it is possible to do.
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Trash80toHP_Mini
NIGHT STALKER
< me doffs redneck gimme hat, bowing in respect for said achievement >
Looks like it's time to read this thread!
Looks like it's time to read this thread!
techknight
Well-known member
I dunno, I think BMOW has me beat with the floppy emulator
Trash80toHP_Mini
NIGHT STALKER
Maybe so, but isn't the Big Tomata' an EE?
.
.
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techknight
Well-known member
Im not sure. I am an EE as well, but only 2-year. Most of my knowledge is experience.
Jumping the gun a bit here, but, if these sell very fast, and you run out of SRAM chips, Mouser has this chip (263 in stock):
http://www.mouser.com/ProductDetail/Alliance-Memory/AS6C1616-55TIN/?qs=sGAEpiMZZMt9mBA6nIyysDfDw0vDQxSw%2fJdd2EqgHt0%3d
It would be about $7 each if you bought 100 of them, but they have the same pinout as the TC55BVM416, are TTL compatible and are in the same package. Probably bump the cost of the card up from $75 to $100, but at least you'd be able to make more of them using the same PCB.
The only issue I see is that the AS6C1616 does not support X8 mode. Only 1M X 16. I'm still not clear on whether you're using the TC55BVM416 in 1M X 16 mode or in pairs as 2M X 8.
http://www.mouser.com/ProductDetail/Alliance-Memory/AS6C1616-55TIN/?qs=sGAEpiMZZMt9mBA6nIyysDfDw0vDQxSw%2fJdd2EqgHt0%3d
It would be about $7 each if you bought 100 of them, but they have the same pinout as the TC55BVM416, are TTL compatible and are in the same package. Probably bump the cost of the card up from $75 to $100, but at least you'd be able to make more of them using the same PCB.
The only issue I see is that the AS6C1616 does not support X8 mode. Only 1M X 16. I'm still not clear on whether you're using the TC55BVM416 in 1M X 16 mode or in pairs as 2M X 8.
techknight
Well-known member
unrelated.
I need someone with good internet digging skills.
Looking for a motorola application note on the 68020.
Motorola AN944
BTW, they are only going to sell as fast as I can make them. lol.
I need someone with good internet digging skills.
Looking for a motorola application note on the 68020.
Motorola AN944
BTW, they are only going to sell as fast as I can make them. lol.
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http://maben.homeip.net/static/S100/motorola/68020/Motorola%20ANE%20001D%20application%20note.pdf
Is that what you are looking for?
