sumane@anaconda.stanford.edu (Thilaka Sumanaweera) (01/05/90)
We have a Personal IRIS 4D/20 (16Mb) and we are going to upgrade it to 4D/25(32Mb). We would like to get 16Mb of additional memory for this. Will the 30-pin SIMMs which fit in the 4D/20 be compatible with the 4D/25? If not, which pin configuration/reference no. should we use when ordering? Thanks in advance, Thilaka sumane@anaconda.stanford.edu
blbates@AERO4.LARC.NASA.GOV ("Brent L. Bates AAD/TAB MS294 x42854") (01/05/90)
I have been told that the 4D/20 and 4D/25 use the same memory. However, if you want 32Mb of memory on the main board you have to use 4Mb SIMMS, ALL of them must be the same. So, if you currently have 1Mb SIMMS, you will have to remove them and replace them with the 4Mb SIMMS. -- Brent L. Bates NASA-Langley Research Center M.S. 294 Hampton, Virginia 23665-5225 (804) 864-2854 E-mail: blbates@aero4.larc.nasa.gov or blbates@aero2.larc.nasa.gov
wiltse@oceana.esd.sgi.com (Wiltse Carpenter) (01/10/90)
In article <9001051539.AA13873@aero4.larc.nasa.gov>, blbates@AERO4.LARC.NASA.GOV ("Brent L. Bates AAD/TAB MS294 x42854") writes: > > I have been told that the 4D/20 and 4D/25 use the same memory. > However, if you want 32Mb of memory on the main board you have to use > 4Mb SIMMS, ALL of them must be the same. So, if you currently have > 1Mb SIMMS, you will have to remove them and replace them with the > 4Mb SIMMS. Whoever told you that 4D/20 and 4D/25 machines use the same memory was right. However, the 32MB maximum memory is achieved by using double- high 1 MB SIMMs, not 4MB ones. They don't all have to be the same, but there are restrictions on mixing them. Basically, it doesn't work to have ``holes'' in the physical memory map. Complicating the matter is the way memory addressing works with dual height SIMMS: one layer at a time. So, all of the SIMM sockets must at least have single high SIMMs in them before the first set of sockets can support double-high ones. 4MB SIMMs haven't yet been qualified for the 4D/2x line and may require a PROM fix to some machines; we're working on it. -Wiltse Carpenter