PC Chips M598LMR - question about memory support

[ivanbuto]

Does anybody know whether the PC Chips M598LMR motherboard supports ECC and/or registered memory? I downloaded the manual from motherboards.org, but it doesn't mention anything about this.
Thanks,


Ivan

[Peter M]

Just like any other shared-memory-VGA chipset out there, no ECC, no registered DIMMs. Just unbuffered 64-bit-wide plain vanilla standard DIMMs, please.

[ivanbuto]

OK thanks. And would you know what maximum chip density it supports - probably 128 Mbit?
I am actually kind of confused about how exactly the whole composition of the memory model works. For example if I have a 256 MB DIMM module with a 32Mx8-bit chipset, do I understand correctly that this means the module is single sided and there are eight chips on the module? If it were a 16x8-bit chipset does that mean there are 16 chips and the module is thus double sided? What about some types of memory where it says 32Mx4 and warns that these are not usable with chipsets like the 440BX (is that because the overall width on one side has to be 64-bit?) And how does the number of banks figure in all of this? For example I have a datasheet for a Kingston 256MB PC100 module which specifies that it has sixteen 16Mx8-bit chips, but that 16Mx8-bit actually means 4M x 8-bit x 4 bank. But in my motherboard manual it says one memory slot is two banks, so how would this work??
I've read all kinds of memory guides and FAQs but I still can't really understand some of these things, so I'd be happy if somebody could explain.
Thanks much.

Ivan

[BipolarBill]

http://www.kingston.com/tools/umg/umg04.asp

[ivanbuto]

Yes, I read that before, but it doesn't fully answer some of the questions I had.

[Tweb]

Here's a good site to start at: http://www.stud.fernuni-hagen.de/q39...ips/index.html

It has better knowelage then the PCChips own home page.

[Peter M]

The "32x8" or "16x8" moniker tells you how the SDRAM chips are layed out.

Now, what actually limits a chipset's ability to address larger sizes of RAM is its maximum count of bank, row and column addresses it can drive toward the RAM.
(Note: Banks are SDRAM chip internal.)

E.g. saying "16x8 RAM" means it's a 128-MBit chip, layed out as 16M cells each 8 bits wide. The 16M cells (here's the point where you'd have to start reading SDRAM datasheets) are layed out as four (2^2) banks, 2^12 rows, 2^10 columns. 32x8 is 2^(2/13/10). Both drive out eight bits of data in parallel when addressed.

Now bank and row address are driven in the same cycle, the column follows in the next cycle of the addressing sequence. So you need to have (2+12) = 14 memory address lines for 16x8 but fifteen for 32x8. And you need eight pieces of these x8 parts to get the SDRAM's standard data width of 64 bits, nine for a 72-bit wide "ECC" DIMM.

So, if you buy a 256-MByte DIMM made from 32x8 devices, you'll get one with eight chips on, forming one rank ("DIMM side") of 256 MBytes. You will need 16 pcs of 16x8 devices to get the same 256-MByte capacity, in two ranks.

That answers your other question - people often say banks too when they actually mean ranks. DIMM slots take two ranks of SDRAM; SDRAM chips internally have four banks.

What is the SiS 530 capable of?

http://www.sis.com/products/chipsets...et7/530fea.htm

says 32xN SDRAM supported, 1.5 GBytes in six ranks. Meaning it'll take single-sided 256-MByte DIMMs, and also double-sided 512-MByte.

HOWEVER ... the individual board's BIOS also must be ready to recognize these DIMMs and set the memory controller up to use them. Hence, YMMV.

[ivanbuto]

Thanks.
What I am not clear about now is the difference between 'side' and 'rank'. My understanding was that each DIMM module takes up two ranks, so for example if I have three memory slots on my motherboard that means I have six ranks. But from what you said, if I have a 256 MB module made of eight 32x8 chip, these chips form one rank. I thought it was one *side*, and I thought what that meant was that the chips are physically present on only one side of the module, whereas if it was double-sided they would be on both sides (2 x eight). So what's the difference between a side and a rank, then?
Do all SDRAM chips have four banks? I have a manual for my motherboard, Abit BH6, and on pages 19 and 20 it contains information about valid memory setups. On pg. 20 there is a table which is really confusing and I can't figure out how it goes together with what I've learned from your previous post. If you have a little time to take a look at it, the manual can be downloaded (it's under 800 KB), at the following site:

http://www.abit.com.tw/abitweb/webjs...LE=BH6&#Manual

Thanks,

Ivan

[Peter M]

16-MBit SDRAMs were the last to have 2 banks. Everything larger has 4.

Ranks vs. sides. You can build one rank from 16 pcs of x4 width SDRAM. You'd then have both sides of the DIMM board physically populated, but you'd still only have one logical rank.

So, you can have double sided DIMMs with one or two ranks. Now, while oftentimes compatibility is discussed in terms of single-/double-sided, the really relevant thing is the ranks, not the physical arrangement of chips.

[ivanbuto]

Sorry, I still don't get this. So what's the definition of a rank? Is it something that's 64-bit wide in total?
In the BH6 manual it says that I have three DIMM slots, each containing two banks (but I guess they mean "ranks" according to what you said). These are labeled 0 through 5. So if I put in a module in the first slot, which would be ranks 0 and 1, but if the module only occupies one rank, does this mean that the computer will interpret this as rank 0 having all the memory and rank 1 being empty?
As for compatibility, on my motherboard I know there is a restriction of chip density max. 128 Mbit. But then why can't I use modules made with 32Mx4 chips? (Is this because I have a 64-bit wide bus, whatever that means?)
Thanks for your help.

[Peter M]

You got it. A rank is a 64 (72) bits wide group of identical SDRAM devices. Each DIMM may contain one or two ranks.

Intel BX can't use 32x4 SDRAM because these are 12x11 row/column addresses, again something the chipset doesn't do. Intel BX maxes out at 2/12/10 bank/row/column signals.

[jrobbinson]

im not sure about the m599 but in the manual of my m598v.7 it says it supports ecc ram and all the utilitys like ADCM by AMI bios which came with the board says yes, but pete said in the pcchip forum said NO.

[Peter M]

Definitely a No here. None of the shared-VGA chipsets ever made so far by anybody support ECC RAM. (Note that ECC RAM is just 72 bits wide instead of 64, and a chipset that doesn't use that simply ignores the extra 8 bits. So it'll still "work", but it won't do any error checking or correction. Waste of money then.)

[ivanbuto]

Hmmm, but on the website for the Amptron PM-598MR motherboard (which is not the same as the PC Chips motherboard, but it seems to be the same in many respects), it says that ECC is supported.
http://www.amptron.com/html/m598mr.html

BTW the table in my manual still doesn't make sense, but maybe there are mistakes there.

[Peter M]

598(L)MR is just the later incarnation, with a newer sound chip, LAN onboard and modem card added.
Still the same SiS 530 chipset there WHICH DOES NOT DO ECC ON THE MEMORY. Period. Check the SiS link I gave above. No matter how many web ads have that wrong.