On Friday, July 11, 2014 9:51:30 PM UTC-5, Gregg Eshelman wrote: > > > It'll go up to 128+4 meg with the right SIMM. >
> IIRC what the SIMMs must have is a lot of small capacity chips due to > the memory controller being unable to work with high capacity chips. > > In other words 2 or 4 chip SIMMs of any size won't work, has to have at > least 8 chips for up to 32 meg. 64 meg would likely have 16 chips and > 128 meg 32. > Eight chips for a usable 64MB SIMM. Sixteen chips for a usable 128MB SIMM. Twelve and twenty-four respectively, if they are parity SIMMs. Samsung made a 5V, FPM/EDO memory chip with 16M X 4 organization and another with 16M X 1 organization. KM44C16000 is the 16M X 4 part. The KM44V16000 is 3.3V, but appears to have 5V tolerant IO. The 16M X 1 part is KM41C16000 for 5V or KM41V16000 for 3.3V supply. The good large capacity SIMMs are typically made of eight of the 16M X 4 chips or sixteen for the larger SIMM. For some reason, on parity SIMMs, they used the 16M X 1 parts to provide parity. 1 bit of parity per 8 bits of data. So a 16M X 32 bit SIMM requires four of the 16M X 1 bit parts to provide parity. The 2 X 16M X 32 (128 MB) SIMM requires 2 X four of the 16M X 1 bit parts to provide parity. Of course the Mac ignores the parity, but often, the parity SIMMs are available and as cheap or cheaper than the non-parity SIMMs. On a parity SIMM, there will be eight fat chips and four narrow chips, 16 fat and 8 narrow for the 128MB SIMM. Jeff Walther -- -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to vintage-macs@googlegroups.com To leave this group, send email to vintage-macs+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/ --- You received this message because you are subscribed to the Google Groups "Vintage Macs" group. To unsubscribe from this group and stop receiving emails from it, send an email to vintage-macs+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
