1764 Ram Expansion Unit (REU) 256kb
When the Commodore 128 came out it was clear that this series of computers was
also intended for business use. And for many even 128 kb wasnt enough. Commodore released
some memory expansion modules, the 1700 (128kb), 1750 (512kb) and then the 1764. The two first
ones was only supported by the 128 and the 1764 was the one that was released for the C64.
Soon after its release a lot of computers were coming in for repairs because the PSU wasnt
powerful enough when the REU was plugged in. So Commodore released this bundle with the
REU and a powerful 2.5 amp PSU. The 6502 cannot address more than 64kb of memory so a special
paging mode would have to be used in order to copy memory to and from the REU. Applications
like GEOS benefitted greatly from the REU and enabled the use of a very nice ram drive to speed
things up considerably.
As usual I found this on ebay UK and was quite lucky to find it complete with box
manuals and all. Its quite heavy due to the powerful PSU. And the unit sticks out quite a bit
in the back of a C64.