Re: Early Amiga 200

From: Gerrit Heitsch <gerrit_at_laosinh.s.bawue.de>
Date: Sat, 23 Nov 2013 15:06:40 +0100
Message-ID: <5290B670.3030608@laosinh.s.bawue.de>
On 11/23/2013 02:12 PM, silverdr@wfmh.org.pl wrote:
>
> On 2013-11-23, at 06:45, Bil Herd <bherd@mercury-cg.com> wrote:
>
>> Good call: There is a sticker near the front that says Rev 6.2 and the
>> copper near the back next to Fish and Haynie''s name is Rev 6
>
> AFAIR thatís not a very early one then. If memory serves, it was Rev. 5, which was a already a common guest in my repair workshop back then. Most visible difference was the RAM x64 vs. x256 in the newer ones.
>

The oldest Amiga 2000 I own is the A2000 designed in Germany (Still 
working, battery has been removed). The chipset from the A1000 combined 
with glue logic for the expansion slots and a memory card in the CPU 
slot allowing up to 1 MB extra RAM. This one is also known as the 
A2000A. It uses a multilayer board while all further A2000 use just dual 
layer PCBs.

Then the guys in the USA took that design and improved it with the 
chipset (PAULA, DENISE, FAT AGNUS, GARY) used in the A500. Also they 
made a custom chip (BUSTER, 5721) that contained the glue logic for the 
expansion slots. This version had 1 MB on board, in 32 x 256Kx1 DRAMs, 
512KB Chip-RAM, 512KB $C00000-RAM. All the mainboards I know of this 
were Rev 4.x (4 to 4.5).

Then came the Rev 6 boards with the new AGNUS (8372A) that was able to 
supply 1 MB of Chip-RAM and handle the refresh for the 8x 256Kx4 DRAMs 
used (The 8371 can't, the refresh counter is too short). This board had 
some signal issues with the Expansion cards which resulted in a rework 
(remove pullups, add pulldowns or such and some other small parts) which 
was known as the Rev 6.2

If you still have an A2000 and have not done so, remove the NiCd battery 
for the clock. It _will_ leak potassium hydroxide solution sooner or 
later and damage the PCB. This applies to all other Amigas with RTC on 
board as well.

  Gerrit





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