Author: Matt Taylor
Date: 13:22:55 03/19/03
Go up one level in this thread
On March 19, 2003 at 14:10:25, Robert Hyatt wrote: >On March 19, 2003 at 12:20:19, Matt Taylor wrote: > >>On March 18, 2003 at 23:26:10, Robert Hyatt wrote: >> >>>On March 18, 2003 at 19:49:17, Tom Kerrigan wrote: >>> >>>>On March 18, 2003 at 18:25:45, Robert Hyatt wrote: >>>> >>>>>On March 18, 2003 at 17:13:13, Tom Kerrigan wrote: >>>>> >>>>>>On March 18, 2003 at 17:02:22, Aaron Gordon wrote: >>>>>> >>>>>>>The motherboard is an Abit BP6. There's also 4-way interleaving on the Abit KT7, >>>>>>>KT7a, BH6, Be6, Be6-2, BX6, BX6-2, etc. Tons and tons of boards support 2 & 4 >>>>>>>way. Also if I recall correctly it treats 1 dimm as "2" banks. Back in the day >>>>>>>when enabling 4-way interleave with two Kingmax PC150 dimms (256mb per) I saw at >>>>>>>least a 20% fps increase in Quake3. I still have the KT7a if you want me to run >>>>>>>any tests. >>>>>> >>>>>>Makes sense. Why have a _DUAL_ inline memory module if it doesn't do >>>>>>interleaving? >>>>>> >>>>>>-Tom >>>>> >>>>> >>>>>How do you transfer > 8 bytes of data from one thing, with only enough pins to >>>>>transfer >>>>>8 bytes at once? >>>> >>>>Well, let's see, because nobody said interleaving = > 8 bytes. >>> >>>THe basic memory bus width == 8 bytes, so interleaving _less_ buys you >>>exactly nothing... >>> >>>> >>>>SIMMs are 32 bits. DIMMs are two SIMMs, and (not coincidentally) 64 bits. DIMMs >>>>are interleaved SIMMs in one package. Get it? >>> >>>I don't know. In that context, I suppose it makes sense. But that is a very >>>poor approach to the issue. However, as to the context of SIMM = 32 bits, I >>>am not certain of that. My quad P6/200 uses SIMMS and it has four banks to >>>interleave 4 X 64 bits according to the docs. And I _can_ have one SIMM per >>>bank and I don't just get 32 bits. Again, I'm not an expert on the details >>>here, but it seems that the SIMMS have more than enough pins to transport 64 >>>bits of data + 8 bits of ECC hamming, in one cycle. >> >>I have a K6 and a Pentium that both use SIMMs. They -require- pairing SIMMs so >>they can be interleaved because the system bus was 8-bytes wide and a SIMM was >>4-bytes wide. >> >>You are right that a 72-pin SIMM has enough pins to transmit 64 bits of data and >>8 bits of ECC in a cycle, but if that were the case I'd wonder where it >>connected to power and ground. Most of the pinouts for the 168-pin DIMM package >>don't involve data pins at all. More than half were related to clocking/control, >>to power, or not connected. I haven't seen the pinouts for a SIMM, but it's >>probably similar. >> >>-Matt > >I'll have to look up the details on my quad P6. Perhaps there was some >fuzziness in the >machine as it had four banks, each bank having four slots, and for my box, all >16 slots were >full. Perhaps allowing a pair of SIMMS to present 8 bytes from one bank? 20 >years ago >these architectural "terms" were much clearer and more precise than they are >today it >seems. The machine probably would not have booted if any bank had either 1 or 3 SIMMs. Yes, the trick was to pair SIMMs and combine the 4 bytes from each to present an 8 byte bus. 20 years ago the PC was fledgling. The confusion is caused by marketting people who don't know the difference between a nibble and a bit (and could care less what either are) but have to sell technical products. Since they're not selling to technical people, they get away with it. The AGP standard is another good example. I have not read all the tech docs, but the bus speed on AGP 8x is still 66 MHz. Nobody explains what 8x means; they just tell you it's 8x. >I suppose one other alternative was to use the same idea as used in EDO/FPM/etc >RAM >and clock the first 32 bits out of a SIMM after the normal latency delay, and >clock the >next 32 bits out on the next clock cycle... > >Perhaps that is my old quad's "solution" to the problem.. Might be. The solution used in the Intel 440TX chipset was to pair the SIMMs and require interleaving to double the bus width. The 440TX is the chipset that my Pentium 120 used, the same board that my K6 runs in now. -Matt
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