🚀 go-pugleaf

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