Memory Upgrade

[Smitty]

Hi
I have a COMPAQ Presario (not as good as I expected). It came with 64MB of ram. I want to add ram and was sold a "stick", 128MB of Azenram, PC133. After more investigation (although I am still not sure) it seems the original module is PC100 variety. Simply put, what are the ramifications of adding the PC133 to existing PC100 type ?
Also according to some COMPAQ literature memory modules are best installed in pairs, but other literature on their site indicates this is not a problem. Finally, since there are (2) sockets which is preferable to use when installing the new "stick" regardless of whether it is PC100 or PC133? I believe they are labelled "A" and "B".

Exact Presario Model is 5BW 157...Azenram website indicates AAP0117 for upgrade. I have AAP0131 (PC133)

Many thanks

Smitty
<P ID="edit"><FONT class="small">Edited by Smitty on 07/19/01 10:38.</FONT></P>

[Paradigm]

The only thing that will happen is that the PC133 RAM is going to work at only PC100 rather than the spec of PC133, which is slower. Don't worry too much about putting the PC133 in with the PC100. Its not gonna burn a hole in your system or anything like that

[Smitty]

Thanks for the tip Paradigm....

I wasn't actually worried about a fire as you so tactfully phrased it.

I think I will wait for a second opinion however. There must be some pro's and con's, otherwise I asked a really dumb question, and that is entirely possible.

Smitty

[Paradigm]

Sorry about the exaggeration...

[renejr]

Original answer is correct. You may use pc133 with pc100 but speed is limited to 100. The reference to using memory "sticks" in pairs was probably in reference to DIMMs, a different kind of memory. SIMMs (pc100/133) can normally installed be installed as singles. Also, they do not have to be of the same size if more than one is used. Not a "dumb" question, you have to know some history for the right perspective.

Rene

[RWSchlatter]

"...memory modules are best installed in pairs,..."
J seem to remember that the reason is memory configurations on the chip carriers. Rule: same memory sizes in one pair.

Assuming your first 64KB may be fixed on the motherboard, you would be free with adding to the slots (often 4).
If one of the slots already holds the 64KB carrier and you add a 128KB carrier, the suggestion would be to put that one in the second pair of slots.
But you should also check and see if all slots need to be filled in sequence.

As much as J remember, your new memory will not be harmed if it doesn't work together with the 64KB chip first, only your machine may not boot properly or operate properly soon after (expect to see Blue Screens in this case). Set full memory test in CMOS during POST when making the upgrade.

If you have problems, either remove the 64KB and run only 128KB, or try and find another 64KB carrier (surplus from older machines), or even get another 128KB as replacement for the 64KB.

______________
Regards - Richard

[Smitty]

The Compaq Maintenance and Support Pages are definitely out of date. In any case if I wanted to substantially improve I assume a matching SIMM of PC133 would be best. I notice the poor old drive grinding away unless I defrag it every 2 or 3 days.
Paradigm, my apologies for being sensitive, I have been pointed in the wrong direction enough to be cautious. Thanks to all others who commented. Keep up the good work Richard.

Smitty

[Andy-S]

Smitty,

Adding your 128MB 133MHz DIMM will provide you with 3 times the memory capacity that you currently have and should reduce the paging to the HDD. Both DIMM's will run at a 100MHz memory bus speed as the ROM automatically downshifts the bus speed to the slowest DIMM (this information is read from an EEPROM on each DIMM). In some cases only the first DIMM is read (normally the one nearest the processor) therefore the 100MHz DIMM should be placed in this slot. I looked at the Compaq guide that ships with your computer and it hints that it is best to upgrade with the same type and speed as what is shipped by Compaq. In this case that would be PC100 SDRAM. The reason for this is that if you select a higher speed DIMM then you will not get the benefits that this technology provides. One caveat to mixing different types and vendors of memory is that you sometimes see timing issues between the modules that will result in lockups, blue screens etc. (as Richard stated previously).

To close on all the other mails. The reason that documentation used to state that memory should be installed in pairs was because in those days the memory modules were SIMMs (Single Inline Memory Modules) that had a single bank of memory. To improve memory access system designers use a method called interleaving where one bank can be pre-charged while the other is being accessed. This reduces the access time but meant that memory had to be installed in pairs to get the two banks. In DIMMs(Dual Inline Memory Modules) the interleaving is done internal to the module and therefore there is no requirement to populate these in pairs.

In short, you should (theoretically) have no issues with using the 128MB DIMM, however you should always be aware of Murphys law (if anything can go wrong it will go wrong) when mixing different types and vendors of memory. Hope this answers your query.

[Smitty]

Again Thanks for the information...I feel I have milked this long enough..
As to Murphy's Law there was of course Seymour's Commentary..:Murphy was an optimist!
/images/w3t/icons/wink.gif
Ooops I just found another problem, will work on it for awhile and if I annot solve it I know where to come.

Catch you Later....[would anyone understand CYL?]