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Old 27 July 2020, 18:31   #1
Retrogradient
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Amiga 2000 - Rev 6.2 has less onboard ram than preceeding boards?

This has confused me quite a bit.



The RAM on the board is the TMS4256-15NL


The Rev. 6.2 boards have 8 of these chips, but the previous boards (Rev 4.x for example) have 32 of these chips.




Whats up with that?


Thank you...
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Old 27 July 2020, 18:37   #2
pipper
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Technological advances. More Storage per Chip.
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Old 27 July 2020, 19:01   #3
Retrogradient
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but its the same chip, and same storage capacity (256kb)...
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Old 27 July 2020, 19:25   #4
Thomas Richter
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Quote:
Originally Posted by Retrogradient View Post
The RAM on the board is the TMS4256-15NL
This is a 265Kx1 RAM chip found on the Rev.4 boards.


Quote:
Originally Posted by Retrogradient View Post
The Rev. 6.2 boards have 8 of these chips...
Actually, the Rev 6.2 boards have 256Kx4 chips, for example TMS44C256-15. Note the additional 4C in its label indicating that it stores 4 bits per cell.
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Old 27 July 2020, 19:55   #5
jasonsbeer
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Quote:
Originally Posted by Thomas Richter View Post
Actually, the Rev 6.2 boards have 256Kx4 chips, for example TMS44C256-15. Note the additional 4C in its label indicating that it stores 4 bits per cell.
This. The part numbers can be confusing, but Rev 5 and up all used 256k x 4 DRAM. Earlier revisions all used 256k x 1.
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Old 27 July 2020, 20:32   #6
Retrogradient
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Hooooo

I was reading about replacement parts on Rev 6.2 (More specifically referencing the Bill of Materials for a replica rebuild) and it called for 4256-10NL parts

539 U501 4256-10 Top Memory chip
540 U502 4256-10 Top Memory chip
541 U503 4256-10 Top Memory chip
542 U504 4256-10 Top Memory chip
543 U505 4256-10 Top Memory chip
544 U506 4256-10 Top Memory chip
545 U507 4256-10 Top Memory chip
546 U508 4256-10 Top Memory chip


Considering the replica boards are Rev 6.2...

Shouldn't these be 44C256-15 / 44C256-10 than ???
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Old 28 July 2020, 01:57   #7
jasonsbeer
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Quote:
Originally Posted by Retrogradient View Post
I was reading about replacement parts on Rev 6.2 (More specifically referencing the Bill of Materials for a replica rebuild) and it called for 4256-10NL parts

539 U501 4256-10 Top Memory chip
540 U502 4256-10 Top Memory chip
541 U503 4256-10 Top Memory chip
542 U504 4256-10 Top Memory chip
543 U505 4256-10 Top Memory chip
544 U506 4256-10 Top Memory chip
545 U507 4256-10 Top Memory chip
546 U508 4256-10 Top Memory chip


Considering the replica boards are Rev 6.2...

Shouldn't these be 44C256-15 / 44C256-10 than ???
Maybe. Depends on the manufacturer. Many (not all) manufacturers designate their 256k x 4 DRAM with a part number containing or ending with 4256-xx. Where the xx is the speed of the DRAM. The bill of materials is simply telling you to look for 4256-10 in the part number. However, it does not have to be -10. The Amiga 2000 Rev 6 specs call for 150ns (-15) or faster. I have been using 70ns DRAMS (-70) to replace the stock ones when needed.

See this link for some compatible DRAM options. http://www.amiga-stuff.com/hardware/256kx4-dram.html
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Old 28 July 2020, 20:03   #8
Retrogradient
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Originally Posted by jasonsbeer View Post
Maybe. Depends on the manufacturer. Many (not all) manufacturers designate their 256k x 4 DRAM with a part number containing or ending with 4256-xx. Where the xx is the speed of the DRAM. The bill of materials is simply telling you to look for 4256-10 in the part number. However, it does not have to be -10. The Amiga 2000 Rev 6 specs call for 150ns (-15) or faster. I have been using 70ns DRAMS (-70) to replace the stock ones when needed.

See this link for some compatible DRAM options. http://www.amiga-stuff.com/hardware/256kx4-dram.html

thanks for the information.

I have been really considering this project of getting a replica board, as the Amiga I bought was quite damaged, and am rather keen on getting it up and going.


These rams in north America look pretty pricey and sparse though.
Thanks.
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