ziggy+@andrew.cmu.edu (John Salmento) (03/10/89)
Since I have received answers to the third question about 512KE, and some people have requested this information I'm going to post all the answers again. >Hi, > I have a couple of questions about Mac simms. I removed two 256K simms from my Mac >Plus, when I upgraded it to 2.5 MB. > >Is there a way to tell the speed of these simms by the age of the Mac Plus, or by looking at the >simms? You can tell the speed by the last two digits on the chip. -15 means 150 ns and -12 means 120ns. >Are Mac simms and IBM simms interchangeable as long as the simms are fast enough? It is possilble to use IBM simms in Macs, but not Mac simms in IBMs. IBM simms are 9 bit chips. The nineth bit is used for parity checking, and according to Lee Larson, "statistical analyses have shown that there is no significant increase in reliability in using that ninth chip as IBM does. It is only used once, during the boot-up process. It has as much chance of failure as any other chip in the system, so 1/9 of the time, the parity chip is the one that goes. (More parts ==> More failures)" >Is it possible to use Mac simms in a 512KE, ie. does the 512KE macs have simms slots? Mac 128, 512K, and 512KE do not have simms; their memory is soldered into the motherboard. It is possible to get simms slots by upgrading; however, not all upgrades have simms slots. Howard Fukuda at CMU gave a nice summary: "1) Apple. Since it's a 512KE, all you need is a motherboard swap. The CMU computer store price is $442 + 6% sales tax = $468.52. This will give you the equivalent of a Mac Plus, except for the keyboard. You will then have 1 meg of RAM in 4 SIMM sockets so you can spend more money to expand it. Of course, you will get an SCSI port if you want a hard drive. 2) Dove. The Dove upgrade basically adds a board connected right above your motherboard. There are two upgrades, 1 meg and 2 meg. I've seen the Dove upgrade advertized for ~$300 for the 1 meg in the April MacUser, but since the time the ad was done, prices could have dropped. The same ad listed the 2 meg for ~$500. The Dove upgrade can also come with an SCSI port, this adds about $100 to the price. Some hard drives are not compatible with Dove's SCSI port. Call companies about this and for recent prices. The Dove upgrade is done entirely in 256kbit chips, so they have 16 and 48 chips respectively. I think the 1 meg board can be expanded to 2 meg by adding chips, but I'm not sure. I am sure that the board limits you to 2 meg of RAM total. The computer store used to sell the 1 meg upgrade, but I think they stopped carrying it. You could check just in case. If you have no preference on where to call, I would suggest Mac Connection. They're friendly have good service, telling if a product is out of stock, and are reliable: certainly one of the most complaint-free mail order company around. 3) Mac Products USA. They sell Dove upgrades, but also have their own line of expansions for the 512KE. The price I saw for the 512-1024 upgrade was $249, but this again could have changed. I know nothing about the details of their upgrade or if it is expandable afterwards. They do sell their own SCSI port also, but I don't think there is an SCSI port for a 512KE that doesn't have or at one time didn't have incompatibility problems with some other manufacturer's hardware. They have a 1-800 number so it should be easy to get the information. CMU Comp Store x2636 Mac Connection 1-800-622-5472 Mac Products 1-800-MAC-DISK" Thanks again to all the people who responded. John Salmento ziggy+@andrew.cmu.edu