CAS Latency and timings.

[High_Jumbllama]

How would one find out the CAS latency of their memory. Could one infer it from their default timings?

For example, I have a 256MB double-sided PC 133 SDRam Dimm in a PC100 Motherboard.

[KeiFront]

It's mostly marked on the memory module with a sticker (3-digit format e.g. 3-2-2).

[Wulfman]

http://heise.de/ct/ftp/ctspd.shtml

this program reads the SPD-settings from installed modules.

mfg
wulfman

[High_Jumbllama]

Usually, but mine did not have this whcih is why I was asking about the timings. If it helps, it is a stick from the defunct Upgradeplanet and was supposedly High Grade so I am guessing CAS2 or CAS2.5.

[High_Jumbllama]

Originally posted by Wulfman
http://heise.de/ct/ftp/ctspd.shtml

this program reads the SPD-settings from installed modules.

mfg
wulfman

Excellent! Thank you! I can muddle my way through the German.

[High_Jumbllama]

Chipset not found on the machine I am at now.

[Wombat]

I didn't think SDR SDRAM could be half values.

[The PIT]

I think you're right Wombat it's either 2 or 3.
Anyway if the ram is pc133 rated it should be able to run at cas2 at pc100 settings more than likely.

[Umfriend]

Oh man, last time I went for a stick of Cas 2 133 Mhz SDR, that guy told me over and over again they only had Cas 2.5.

I am a computer illiterate, but this.....even I knew.

[High_Jumbllama]

Originally posted by Umfriend
Oh man, last time I went for a stick of Cas 2 133 Mhz SDR, that guy told me over and over again they only had Cas 2.5.

I am a computer illiterate, but this.....even I knew.

I didn't. Hehe. I had a nimrod at a computer show insist that there were no SlotA thunderbirds. I immediately walked away. Some young punk that was probably working for his daddy.

Interesting, I still want to match up the ram though. If a PC133 CAS3 stick of ram is set in a PC100 motherboard, will it still default to CAS3 even though it can do CAS2 at the lower speed since it defaults to the SPD settings?

[az]

Can you post a pic big enough that the numbers are readable? Or, on second thought, can you post the numbers?

How the automatic speed detection decides is different from board to board, and depends on your stick's SPD EEPROM a lot. Almost all SPD EEPROMs don't contain the proper values. If the BIOS has to guess, it uses the slowest value available.

AZ

[Wombat]

It's likely may not <I>have</I> SPD settings, especially SDR RAM. I think that's registered vs. unregistered.

Yeah, it will probably default to CAS3, just because that's the safe value, but if it doesn't run CAS2 I'd be surprised.

[High_Jumbllama]

Originally posted by az
Can you post a pic big enough that the numbers are readable? Or, on second thought, can you post the numbers?

How the automatic speed detection decides is different from board to board, and depends on your stick's SPD EEPROM a lot. Almost all SPD EEPROMs don't contain the proper values. If the BIOS has to guess, it uses the slowest value available.

AZ

Gonna have to take it to work and scan the module on both sides. I don't have a flatbed scanner here at home. It does seem to be CAS3 or defaults to it at least:

Page Idle Timer 8
Precharge time 3
Ras Activate Timer 5
CAS Latency 3
RAS to CAS Delay 3

[Kurt]

Originally posted by az
Can you post a pic big enough that the numbers are readable? Or, on second thought, can you post the numbers?

How the automatic speed detection decides is different from board to board, and depends on your stick's SPD EEPROM a lot. Almost all SPD EEPROMs don't contain the proper values. If the BIOS has to guess, it uses the slowest value available.

AZ

yep...that's because not all manufacturers have mastered BIOS programming...it's usually best to start with a known working stick then manually change the values and insert the new stick...

[az]

Wombat, IIRC registered and unregistered has nothing to do with the SPD, which, again IIRC, is part of the JEDEC standard. Registered DIMMs have some kind of buffers on them, to make bigger moules less problematic, though a tad slower, IIRC³.

Jumbllama, those seem to be the default timings.

AZ