Old memory in and even older computer

Feb 16, 2005
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I am updating an old HP desktop that one of my relatives has. The memory that is in there now is PC66. Since I can't get this anymore and PC100 is also hard to find I was going to get 2 128mb modules of PC133.

I'm pretty sure this will work except I've heard of people having problems where the computer recognizes only half the installed memory. From what I have read this only happens when the new PC133 memory is of the high-density type. What does this mean? Does it have something to do with the number of chips on the card eg. 16x8 or 16x16?

Also, the users manual for the computer calls for "4-clock" RAM. Is this some latency number?
 

JimPhelpsMI

Golden Member
Oct 8, 2004
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Hi, Chips of same specs except for speed were all manufactured at the same time. They are then tested and the max speed they run minus about 10% is the speed they get marked. Your PC133 will just run the speed the Mother Board is capable of. Jim
 

Wolfshanze

Senior member
Jan 21, 2005
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You can put PC133 memory in a PC66 system... it's no problem... it will run at whatever speed the BUS of the MB runs at (which in this case is probably 66MHz).
 

redbeard1

Diamond Member
Dec 12, 2001
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A number of manufacturers left out support for 133mhz ram in their bios. Dell and HP were the biggest names. In this case, the systems would not post with 133mhz ram.

In the case of a computer only seeing half of the RAM, this happens when you install high density ram in an Intel chipset or old Via and ALI based boards. Nowadays the majority of cheap 133mhz ram is high density.

The best way I know around the issue is to go to Crucial and run their memory chooser to see if they have ram for the system. If they do, it is guaranteed to work. If they list the model, it will also tell you if it can use 256 meg of ram. Some systems had limits placed on them by the manufacturer, even though the chipset could handle it.
 

Nick5324

Diamond Member
Aug 19, 2001
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Originally posted by: redbeard1
A number of manufacturers left out support for 133mhz ram in their bios. Dell and HP were the biggest names. In this case, the systems would not post with 133mhz ram.

In the case of a computer only seeing half of the RAM, this happens when you install high density ram in an Intel chipset or old Via and ALI based boards. Nowadays the majority of cheap 133mhz ram is high density.

The best way I know around the issue is to go to Crucial and run their memory chooser to see if they have ram for the system. If they do, it is guaranteed to work. If they list the model, it will also tell you if it can use 256 meg of ram. Some systems had limits placed on them by the manufacturer, even though the chipset could handle it.

Wow, great response :thumbsup:
When I read the OP, I had a flashback to many years ago when I was looking to buy some RAM for a computer. I remember the guy asking me if I needed "regular or PC100". :D
 

xgsound

Golden Member
Jan 22, 2002
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Which new memory works in a PC66 mem system is very hit or miss. I'm assuming the HP is 400 Mhz or less since it has PC66 mem. Keep in mind if the guaranteed to work crucial memory is $200, that's 1/2 the cost of a budget system from Compaq, emachine, or HP. If the price is $50 to $100 that's not so bad. So check that price first. Those new machines would all be much faster and accept current memory and peripherals better, so I'd say don't go over $100 for the memory.


Jim