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First post, by retro games 100

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Some mobos I've tested accept either PC-66, PC-100 or PC-133 speed SDRAM as their "maximum speed" RAM. I understand you can install higher PC-133 speed SDRAM in mobos such as "PC-100 maximum speed" mobos, for example. I've not tried PC-133 speed SDRAM in a "PC-66 maximum speed" mobo, but I expect it would work.

My question: say if PC-133 SDRAM works in all different types of "PC-??? speed" mobos, is this RAM the best SDRAM to buy? Is there any reason at all to buy for instance PC-66 SDRAM for boards that only accept PC-66 SDRAM? (This same question applies for buying PC-100 SDRAM for a "PC-100 maximum speed" mobo.)

Reply 1 of 9, by Old Thrashbarg

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For the most part, you can get away with PC133 in just about any SDRAM board. As long as you stick with stuff from known brands, you shouldn't have any problems.

I've only ever seen two compatibility issues. First of all, the high-density versus low-density issue. There are a large number of boards that won't accept high density memory, i.e., stuff with 64x4 or 128x4 chips.The density has nothing to do with the speed itself, but you most commonly find those chips on cheap generic PC133 in 256 and 512MB capacities.

The other rare exception is that some PC133 doesn't include SPD settings for PC66 speed. I think you'd generally only run into that on some of the super high-performance PC133 and PC150, since they never expected you to underclock such RAM that far anyhow. I've only ever seen that issue once, though, and the board was already a bit picky about RAM to begin with, so I'd say it'd be safe not to worry about it.

Reply 3 of 9, by Old Thrashbarg

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Yeah, RAM is locked to FSB speed in most older systems. I think he was asking whether it was advisable to buy PC133 and just use it at 66 or 100mhz in such systems, so he wouldn't have to keep track of several different types of RAM... rather than keeping PC66, PC100 and PC133, just use PC133 for all of it.

And yes, there's generally no problem with doing that.

Reply 4 of 9, by retro games 100

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Very interesting, thanks guys! I had a look on ebay, and there's tons of SDRAM (at various speeds) still available, so I'll probably get a bunch of PC-133 sticks, and just a few sticks of 100 & 66, just for "completeness" 😀

Reply 5 of 9, by Old Thrashbarg

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Just be very careful about the stuff on eBay, if you can't see for sure that it's standard low-density RAM, don't touch it... a lot of the sellers are not entirely honest about that detail.

Reply 6 of 9, by Malik

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Old Thrashbarg wrote:

... a lot of the sellers are not entirely honest about that detail.

That and many of them are not aware of what they're selling. For them, PC-100 or PC-133 doesn't make much difference, except that PC-133 is "probably newer" and "faster".

I've successfully used PC-133 SDRAMs on a PC-100 max supporting motherboard. My DFI P2XBL Pentium II/III mobo accepted it. Another motherboard, (can't remember which, with the same PC-100 FSB-linked limit), refused to boot with the PC-133 modules.

5476332566_7480a12517_t.jpgSB Dos Drivers

Reply 7 of 9, by Old Thrashbarg

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For them, PC-100 or PC-133 doesn't make much difference, except that PC-133 is "probably newer" and "faster".

I'm not talking about PC100 vs PC133, I'm talking about the density of the memory chips used. The so-called high-density RAM sold by a great many of the eBay sellers does not follow JEDEC specs, and will not work in most SDRAM systems. Problem is, many sellers know this fact, and will add caveats that you should check compatibility, but they also don't always mention that it's high-density.

Reply 8 of 9, by bushwack

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I was looking SDRAM on ebay a few days ago, I have some to sell but there is so much and it's all so cheap I just put mine back up on the shelf.

Grab some matching name brand sticks from the likes of Crucial, Kingston or Corsair.

Reply 9 of 9, by zapbuzz

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My appologies for bumping an old thread but I had to put some life into it since it was a search result in google and did something about it.
I have done some testing.
My 512mb sticks of single chip sided sticks vs 2 chip sided sticks - single sided access faster. This I would assume be due to Single data rate.
Having to access 2 chip sides with single io access process.
DDR however double chip sided sticks are faster than single - Double data rate optimal on double chip sided sticks.
Access 2 stick/chip sides with an access process simultaneously to reduce latency.
So with SDRAM I recommend single chip sided sticks due to single data rate.
But double chip sided sticks of pc133 sdram outlasted my single sided ones in the past must be density.
Perhaps someones youtube production? But with DDR single chip sided are way cheaper and put into budget pc's and laptops and suck.
(tested DDR400, DDR2, DDR3, DDR4)