dnp@sonia.math.ucla.edu (10/30/89)
To all those wishing to upgrade their NeXT's memory without paying
extraordinary prices. I looked into this matter a while back and these
are the results (please forgive any inaccuracies):
1) The NeXT is fairly kind about memory. Pretty much any SIMM module will
work provided that you use the "standard" configuration(s). As far as
I know this is 4 MegaBytes or 4 modules at a time. For example,
4 1-MegaByte Simms will bring your cube from 8MB to 12MB. Also,
1 4-MegaByte Simm will do the same (these are rare and VERY expensive).
If you have old Mac memory lying about (the 256K variety) you can
put these to good use, 4 256K-Simms will give you an extra 1 MB (wow!).
Naturally 8 1-MB SIMMs or 2 4-MB SIMMs will top your cube off at 16MB.
The basic rule to remember is at least 4 boards or 4 MB's in a single
bank (a "bank" being 4 slots usually). Being cheap and using say 2 1-MB
SIMMs (to get 10MB) will not work. Rumor has it that other configurations
are possible by changing some system register via the system monitor (I
don't mean the display monitor, I mean the display you get when you do a
"<command> <Alt> ~"). I think it's something in "scr2" (clues anyone?).
2) What kind of SIMMs? You need at least 256K 1x8 100ns SIMMs. At present
the NeXT comes with at least eight 1MB 1x8 100ns page mode SIMMs. That is, each SIMM is 1MB, no parity, page mode, 100 nanoseconds access time.
You can use 1x9 (parity), nibble mode, less than 100ns memory (or any
permutation of such). These also can be mixed as along as they follow
the (a) configuration. I use two 1x9 1MB 80ns SIMMs and two 1x8ns 1MB
80ns SIMMs in a single bank and things are just fine.
3) What is the difference between the various SIMMs? First is size, either
256k, 1MB, 4MB (are the standard values) These are self evident.
Second is parity, 1x8 (read "1 by 8"), 1x9, 256x9 etc. This first
digit refers to how the memory on each chip is accessed and the second
is the number of chips. Usually the computer stores data as 8-bi t
characters, one bit per chip in k levels (where k=256, 1MB, etc.); if a
9'th chip is present, it is used for parity (often used to insure the
integrity of data). At present the NeXT does not use parity. Lastly the
mysterious question or "page" vs "nibble" mode memory. You may have heard
these terms in reference to "virtual memory" or software memory moves
(i.e. copying one block of memory to another). For hardware memory
this refers to how the data in the chip can be accessed. For "nibble"
memory data can be accessed one "byte" at a time. That is, the processor
(or memory management unit (MMU)) sets an address of a particular memory
location and the chip outputs the data at that address (the time interval
between giving the chip an address and outputing data is the "access time",
e.g. 100ns, 80ns etc.). In "page" style memory, the chip is given a starting
address and a block size. The chip will then dump data from(starting address)
to (starting address+block size). These days more than 95% of the SIMMs
are page mode, so you probably won't ever see any nibble mode SIMMs
However, at present the 4MB SIMMs are nibble mode. Regardless of
this, the NeXT uses a MMU to negotiate usage, so you can use both page
and nibble mode memory.
4) What should you buy and where? I recommend 1x8 1MB 100ns page mode
SIMMs from Technology Works in Austin Texas. They go for around $96
each (remember you need at least 4). They are a very good company,
offering a lifetime warranty and excellent shipping service. They
will accept university P.O.'s and credit cards or whatever. I was told that
if I could gather enough simultaneous orders that there would be a
substantial discount. If you're interested in doing this, send me your name,
address, and how much you want to order. After a reasonable amount of
time I will find out how much of a discount we can get and we'll take it
from there. Here is their address:
Technology Works
4030 Braker Ln. West, Suite 350
Austin, TX 78759
Voice: 512-794-8533 Fax: 512-794-8520
6) **** WARNING ****
If it is true that NeXT will be upgrading soon to a 50mhz 68040 the present
memory may be too slow (probably not though). I'm sure NeXT will
not replace your 3'rd party memory. However, if this is the case I'm
guessing the resale value of 100ns 1MB SIMMs will be at least %70 of what
you will pay now until next year. Besides, it's not that expensive compared
to what you might pay NeXT for the extra memory.
Corrections, comments, flames, sign-up's for discount to:
Reply's to: dnp@math.ucla.edu In real life: Dan Portgessel@cs.swarthmore.edu (Daniel Mark Gessel) (10/31/89)
In article <1945@sunset.MATH.UCLA.EDU> dnp@MIT.UCLA.EDU () writes: > 6) **** WARNING **** > If it is true that NeXT will be upgrading soon to a 50mhz 68040 the present > memory may be too slow (probably not though). Does anybody know if this is true? If so, any details on what it means to upgrade? Cost? etc. ? Daniel Mark Gessel -- CS Net: gessel@cs.swarthmore.edu UUCP: {bpa,cbmvax,liberty}!swatsun!gessel