I believe c128 came as standard with either 4164 or 41464s 41256 used on c128 ram upgrade (ftp://www.zimmers.net/pub/cbm/documents/projects/memory/c128/1028/1028.html) is 8 bit refresh (256 cycles) http://www.datasheets360.com/pdf/-6344842929410839446 414256 is 9 bit refresh (512 cycles) http://www.datasheets360.com/pdf/5352161926448073490 The apple 2 apparently doesn't have dram refresh, it uses the video fetches to refresh the memory. I'm not sure why the c64 is different. On 12/10/2016 20:58, Terry Raymond wrote: > Hi all, > Are the 41256 Ram that was used on C128 or way earlier? > > Terry Raymond > > On Wednesday, October 12, 2016, Gerrit Heitsch <gerrit@laosinh.s.bawue.de> > wrote: > >> On 10/12/2016 07:34 AM, Marko Mäkelä wrote: >> >>> Hi Ruud, >>> >>> On Wed, Oct 12, 2016 at 05:15:44AM +0000, Baltissen, GJPAA (Ruud) wrote: >>> >>>> Hallo Gerrit, >>>> >>>> >>>> 41256 need 8Bit refresh... >>>> Nope. Otherwise the Finnish's and the 64'er's 256 KB hack on the C64 >>>> wouldn't >>>> have worked. >>>> >>> The VIC-II in the C64 (as well as the VIC-IIe in the C128) implements an >>> 8-bit refresh counter. That was proven in 1994 by the test program that >>> Andreas Boose wrote, to check which memory addresses the VIC-II chip is >>> reading. >>> >> There was no need to prove that... VIC (and TED) _has_ to supply an 8Bit >> refresh since the 64Kx4 DRAMs and some of the 4164 need it. If VIC was only >> doing 7Bit, Commodore would have been limited with the 4164 they could use >> and the 250466 and 250469 boards couldn't exist. >> >> So when replacing 4116 DRAMs with 4164, make sure what kind of refresh >> your system supplies. If you don't know, use 4164 that only need 7Bit >> refresh. To find out, grab the datasheet. >> >> Gerrit >> >> >> >> >> >> Message was sent through the cbm-hackers mailing list >> Message was sent through the cbm-hackers mailing listReceived on 2016-10-12 22:00:02
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