| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 2996.1 | It's very important.. | PUERTO::ALVAREZ | So much work to do...so little time | Fri Oct 06 1989 17:51 | 14 |
| I'm no expert, but with databook in hand...
DRAMs (Dynamic RAMS) require a periodic refresh of its
contents. This is triggered by an external sequence of signals.
One mode of refresh is CAS before RAS. If M.A.S.T. designed its
board to make use of CAS before RAS refresh mode, then you MUST
add DRAM chips which were designed with this feature.
If you get vendors and part numbers, I can try to tell you
if they support this refresh mode, as I have access to several
vendor databooks.
Regards,
Miguel A. Alvarez
|
| 2996.2 | DRAM refresh modes | MEMORY::SOVIE | If u can rd this, you're too close! | Fri Oct 06 1989 17:53 | 16 |
|
CAS before RAS is a special REFRESH mode some DRAM chips have and others
do not, ( most late generation chips have this mode, some early 64Kx1
do not etc. ) Specifically these chips have their own on board
refresh address counter, and all the memory board manufacturers
have to do to enter this special mode is by asserting CAS first and then
RAS, This makes the board manufacturer job easier and reduces device
counts etc.
This is really only important to you if M.A.S.T Minimegs requires
a DRAM with the CAS before RAS feature.
Where did you hear these warnings from??? M.A.S.T ?
Dean
|
| 2996.3 | | PUERTO::ALVAREZ | So much work to do...so little time | Fri Oct 06 1989 17:54 | 5 |
| I would like to add that CAS before RAS seems to be a very common
refresh mode supported by most (if not all) DRAM vendors, so you should
not have a major problem getting chips.
Miguel A. Alvarez
|
| 2996.4 | didn't have this info with me at work | NAC::BRANNON | value added | Sat Oct 07 1989 00:47 | 15 |
| Zip chips that work in the Minimegs have a large T on them for
Toshiba and the number TC514256Z-10. Are they RAS before CAS?
The other clue was that it was rarer than the more common method,
and the Japanese memory chips were most likely to have it.
I heard this from a friend and it was confirmed by a memory vendor
at the last computer show in Woburn, Mass.
The chips I'm considering are Samsung and no I don't have the part
number. I'll get more details at the computer show in Marlboro, Mass
tomorrow.
thanks for all the quick responses,
dennis
|
| 2996.5 | Still need to ask the Minimegs... | PUERTO::ALVAREZ | So much work to do...so little time | Mon Oct 09 1989 10:03 | 8 |
| Yes, the Toshiba chips have the RAS before CAS refresh mode.
However, they also have the more common method called "RAS-only".
This is true of most modern DRAM, having two or more refresh modes.
The module designer then chooses which mode to implement in his
logic. So, by just looking at the DRAM chips, you can't be 100% certain
that the module designer(s) choose RAS before CAS.
Miguel A. Alvarez
|