Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!usc!henry.jpl.nasa.gov!elroy.jpl.nasa.gov!zardoz!dhw68k!thecloud From: thecloud@dhw68k.cts.com (Ken McLeod) Newsgroups: comp.sys.mac Subject: Answers to RAM SIMMs/IIci questions (long) Message-ID: <26707@dhw68k.cts.com> Date: 26 Sep 89 08:38:55 GMT Reply-To: thecloud@dhw68k.cts.com (Ken McLeod) Organization: Wolfskill & Dowling residence; Anaheim, CA (USA) Lines: 126 The following information comes from the "IIci Technical Tour" stack, and hopefully should answer at least some of the questions that have been posted here recently. The usual disclaimers apply. --------------------------------------------------------------------- oo Memory Upgrade Issues oo To satisfy the timing requirements of the 25 MHz 68030, the IIci requires a RAM speed of 80 ns or faster. To satisfy the requirements for burst reads, the IIci requires RAM that supports fast page mode. Use of RAM that does not satisfy both requirements will cause the IIci to crash. The part numbers for Apple labeled SIMM upgrades and service parts that meet these requirements are listed below: Finished Goods RAM Upgrade Packages: Upgrade Size Part Number --------------------------------------------------- 1MB, 80 ns, Fast Page Mode M0291LL/A 4MB, 80 ns, Fast Page Mode M0292LL/A 4MB (Parity), 80 ns, Fast Page Mode M0294LL/A Service Goods RAM SIMM Parts: RAM Density Part Number --------------------------------------------------- 256KB, 80 ns, Fast Page Mode 661-0519 1MB, 80 ns, Fast Page Mode 661-0520 1MB (Parity), 80 ns, Fast Page Mode 661-0546 Unknowing or curious users will undoubtedly try RAM SIMMs that are rated slower than 80 ns. In most cases, those users will find that the slower RAM will work for a short time. However, the IIci unit WILL eventually crash with a serious system error. There are several reasons why a IIci will not always crash immediately on power up when slower RAM is installed. They include: o Frequently, RAM speed is rated conservatively. As a result, a chip may actually be faster than it is rated under certain circumstances. o Many of the RAM SIMMs that are available on the market for use in the Macintosh SE/30, II, IIcx and IIx, including some sold by Apple, are rated for 100 ns, which puts them close to the 80 ns requirements. o RAM speed is higher in a cooler chip than in a warmer chip with the same rating. When the Macintosh is first turned on, the chips are cool. After the unit is turned on, the chips will heat up, which causes them to slow down. The rules that must be followed when installing RAM SIMM modules in a IIci are: o All SIMM boards within a bank must be the same density. o Within a bank that contains RAM, all four slots in that bank must be filled. NOTE: Although the following two rules apply to RAM configurations in all other modular Macintosh models, they ARE NOT required in the IIci. o All SIMM boards must be installed in Bank A for configurations that fill only one bank. o Higher density SIMM boards must be installed in Bank A for configurations that have different densities in each bank. Bank A and Bank B each hold 4 SIMM strips. The following Apple memory upgrades work in the IIci: Bank A and B: Can hold SOJ (small) or DIP (tall) SIMM strips. Upgrade Options for each bank: o One M0291LL/A Apple 1MB Memory Expansion Kit (1MB) o One M0292LL/A Apple 4MB Memory Expansion Kit (4MB) or o One M0294LL/A Macintosh 4MB Parity Memory Expansion Kit (4MB) 1MB IIci (Starting Configuration): End Cofig. Upgrade Needed ---------------------------- 1MB *1 2MB 1-M0291LL/A 4MB 1-M0292LL/A *1, *2 5MB 1-M0291LL/A *3 8MB 1-M0292LL/A 4MB IIci (Starting Configuration): End Cofig. Upgrade Needed ---------------------------- 4MB *1 5MB 1-M0291LL/A *3 8MB 1-M0292LL/A 4MB Parity IIci (Starting Configuration): End Cofig. Upgrade Needed ---------------------------- 4MB *1 5MB *4, *3 8MB 1-M0294LL/A *1 - To achieve this configuration, all four SIMM modules can be installed in either Bank A or Bank B. If built-in video is to be used, all four must be installed in Bank A. If all four are installed in bank B, built-in video will be disabled. *2 - To achieve this configuration, the new SIMM modules will be installed in place of the original SIMM modules. *3 - To maximize performance, install the 1MB SIMM modules in Band B and the 256KB SIMM modules in Bank A. Although the opposite configuration can be installed, the effects of cycle stealing for built-in video can be minimized by installing the smaller of the two in Bank A. *4 - Apple is not offering 256KB Parity SIMM modules, so this configuration would have to be achieved with third-party 256KB SIMMs. --------------------------------------------------------------------- -- ========== ....... ============================================= Ken McLeod :. .: UUCP: ...{spsd,zardoz,felix}!dhw68k!thecloud ========== :::.. ..::: INTERNET: thecloud@dhw68k.cts.com //// =============================================