CRIMMS? Huh?

Nundaska

Distinguished
May 29, 2002
15
0
18,510
I saw somewhere that when u use RDRAM that u needed identical pieces of ram workin in pairs. So if I just want 1 stick of 256MB RDRAM PC-1066 it won't work because i NEED to have them in pairs? And also, it says to fill in empty ram slots with dummy sticks of RAM called CRIMMS? I think it's called CRIMMS... I forgot where I read this =P anyways do these CRIMMS come with the mobo?
Thx in advance for replying.
 

jammydodger

Distinguished
Sep 12, 2001
2,416
0
19,780
Yeh your right a CRIMM is a continuity module, I dont think you get them with the motherboard no. But u can buy them for about £4(in the UK) I not sure how much they cost in America.

Why use windows when you can use doors?
 

bum_jcrules

Distinguished
May 12, 2001
2,186
0
19,780
That is not correct. PC1066 uses the RIMM 4200. The form factor is different than that of a 16 bit RIMM. 16 bit RIMM has two keys and the RIMM 4200 has one large key. Also there are 184 pins on a 16 bit RIMM and 232 on a RIMM 4200. In addition PC1066 (32 bit) has termination resistors on the PCB. (Printed Ciucuit Board) 16 bit (PC800) modules do not. Their termination resistors are on the motherboard itself. Also, PC1066 uses both channels. So you only need one module and one CT-RIMM. (C-RIMM is for 16 bit RIMM and CT-RIMM is for (32 bit) RIMM 4200.)

Tom's did a nice piece on this in their <A HREF="http://www17.tomshardware.com/mainboard/02q2/020624/index.html" target="_new">Warp Speed with Rambus: Six Boards for PC1066</A> article.


<b>"Sometimes you can't hear me because I'm talking in parenthesis" - Steven Wright</b> :lol:
 

Nundaska

Distinguished
May 29, 2002
15
0
18,510
yeah, I already read that article... but I was still a bit confused. So right now my understanding of this is that, with the new PC-1066 RDRAM, I can use a single stick of i wished, but still need to pair it off with a stick of C-RIMM. RIght now i'm looking at buying Gigabyte's GA-8IHXP and it has 4 RAM slots. So if each piece of ram needs to be paired off with a C-RIMM does that mean I can only have 2 sticks of RAM on that board?
 

HokieESM

Distinguished
Apr 22, 2002
34
0
18,530
MOST PC1066 is standard RDRAM... you need PAIRS of RIMMS. Most of the PC1066 MBs have 4 slots... you can either use one or two PAIRS of RAM. If you chose one pair, then you fill the empty slots with CRIMMS (the MB should include them). If you chose to upgrade, just pull the CRIMMS out, and put in RAM.

There ARE some RDRAM "modules" called RIMM4200, and, yes, you only need one of them. The only MB that I know of right now that supports this standard is the ASUS P4T533 (not P4T533-C... which isstraight PC1066). Its also very difficult to find the RAM.

Anyhow, I have a similar setup (a P4T533-C, a P4 2.26GHz, and 512MB of PC1066--one pair of 256MB RIMMs) and it works beautifully. Best of luck to you!
 

bum_jcrules

Distinguished
May 12, 2001
2,186
0
19,780
"MOST PC1066 is standard RDRAM" This is correct, sorry I made it confusing.

Going forward in the future, however, you will have to make sure your motherboard has RIMM 4200. The for factor is changing to that. The clock generators will also corrispond to the new RIMMs. Current RIMMs can only support up to certian speeds. Most, if not all, should be able to give you a 600MHz signal. So the highest you could go is PC1200.

For your situation...

So if your current board is a 16bit RIMM then you should be able to support PC1066. (Speed is 533MHz from the clock generator.) You will need pairs of it however. And if you want all of the memory to run at PC1066 speeds, all of the memory needs to be PC1066. If you keep the PC800 modules in their RIMMs the clock generator will run all of the memory at the lowest speed. (aka 400MHz or PC800 signal.)

You should have the C-RIMMS that your motherboard manufacturer supplied originally. So put one stick in each channel and one C-RIMM in the other for each channel and you should be fine. Again, if you leave the PC800, PC700, or PC600 in the other RIMMS, the clock generator will scale back the speed to the slowest speed.

<b>"Sometimes you can't hear me because I'm talking in parenthesis" - Steven Wright</b> :lol:
 

Crashman

Polypheme
Former Staff
Read this post and the one that follows. IF you have a PIII RDRAM system (i820 or i840), you can use a single PC600, PC700, or PC800 RIMM (PC1066 might not be detected properly by BIOS). If you have a P4 RDRAM system, you need to use pairs. PC1066 is nothing more than a faster version of PC800, it uses the same slots. And P4 RDRAM boards come with four slots and two CRIMMS, since you have to mount the memory in pairs you will never need more than 2 on those.

<font color=blue>At least half of all problems are caused by an insufficient power supply!</font color=blue>
 

Crashman

Polypheme
Former Staff
PC1066 is not 32 bit, it's 16-bit. PC4200 is 32 bit. Both PC1066 and PC4200 run at the same speed, but the former is 16-bit and the later 32 bit.

<font color=blue>At least half of all problems are caused by an insufficient power supply!</font color=blue>
 

eden

Champion
So on P4 RDRAM boards, you always need to fill all slots? Why so, if you had to fill only 2 which are in pairs?

And what happens if you had 3 sticks? Is one C-RIMM all you need to ensure the Dual Channeling of everything?

I'm sorry for these questions, just when I think I finally got the CRIMM's definition, there are always new questions and then answers that mix me up even more.

--
:smile: Intel and AMD sitting under a tree, P-R-O-C-E-S-S-I-N-G! :smile:
 

Crashman

Polypheme
Former Staff
The i850 chipset is DUAL CHANNEL because RIMMS are 16-bit, so a pair was needed to match the bandwidth of the 400MHz bus with PC800. You see, the CPU to memory bus of all modern PC processors is 64-bits. Well, 64-bits at 400MHz has the same bandwidth as 800MHz at 32-bits. So they needed a pair to get 32-bits, so they made a chipset that only operates in that configuration.

The reason you need CRIMMs in the empty slots is that even though the slots are parallel to each other in matched pair, each pair is serial to the next. You have to complete the circuit.

So that only leaves you two choices, 2 RIMMs + 2 CRIMMs, or 2 RIMMs + 2 RIMMs (2+2=4).

The only reason you could use single RIMMs on the earlier PIII boards is becuase there was no need for anything of wider bandwidth on a CPU that only had a 100/133MHz single data rate bus.

<font color=blue>At least half of all problems are caused by an insufficient power supply!</font color=blue>
 

bum_jcrules

Distinguished
May 12, 2001
2,186
0
19,780
I was overloaded at work that day. Let me correct another of my confusing hurried statements.

PC1066 with the new PCB form factor that fits the RIMM 4200, is the 32bit module for the next round of RDRAM memory architecture. (See page 4 of the <A HREF="http://www.rambus.com/rdf/presentations/RIMM3264_06.12.pdf" target="_new"><i>Rambus® 32 and 64 bit RIMM™ Module - Technology Summary</i></A> Note: That paper is from June 2001 and some things have changed, but you get the idea.) For the current PC1066 under RIMM 1600 and RIMM 2100, all are 16-bit. (Well except any engineering samples with the RIMM 1600 and RIMM 2100 form factor.) Here is another good paper on the RIMM 4200 showing the up to date layout of the RIMM 4200 module, use of both channels, clock speeds, etc. (Plus it is only 3 pages long...good for those who can only do a quick read.) It is the <A HREF="http://www.rambus.com/downloads/rimm_4200_white_paper.pdf" target="_new"><i>Rambus RDRAM® RIMM™ 4200 white paper - By Mike Feibus, Feibus SC -May 2002</i></A>.

As for PC1066 modules themselves...

"<font color=green>The 512/576 Mb RDRAM devices are extremely highspeed CMOS DRAMs organized as 32M words by 16 or 18 bits. The use of Rambus Signaling Level (RSL) technology permits 600 MHz to 1066 MHz transfer rates while using conventional system and board design technologies. 1066 MHz RDRAM devices are capable of sustained data transfers at 0.9375 ns per two bytes (7.5 ns per sixteen bytes).</font color=green>" - Taken from page 1 of the <i>Rambus 1066 MHz RDRAM 512/576Mb (8Mx16/18x4i) Advance Information Fact Sheet</i>. Look at page 16 and 17 of the <A HREF="http://www.rambus.com/rdf/presentations/1_05_RambusRoadmap_Fox.pdf" target="_new"><i>RDRAM RDRAM® Device and Device and RIMM RIMM™ Module Roadmap Module Roadmap - Frank Fox Frank Fox - VP, RDRAM Standards Division VP, RDRAM Standards Division Rambus Inc. Rambus Inc. - October 22, 2001 October 22, 2001</i></A> for a good explination for the 16 bit, 32 bit, and 64 bit module designs for the existing form factor using the RIMM 1600 and the RIMM 2100. But as you have seen from the Tom's, <A HREF="http://www.tomshardware.com/mainboard/02q2/020624/i850e-02.html" target="_new">Warp Speed with Rambus: Six Boards for PC1066</A> article you can see the RIMM 4200 form factor. It looks like they are using what they had designed for the form factor for the 64 bit. (See all of the Rambus papers above.) It looks like they needed to eliminate one of the keys for the extra pins. {That is just my speculation...}

Again, I apologize for the confusion... If the are any more mistakes please point them out so I can correct and/or clearify them.

Back to you...

<b>"Sometimes you can't hear me because I'm talking in parenthesis" - Steven Wright</b> :lol: