<< I have a 7300. I recall somebody talk about interleaving RAM sticks. What does this mean and why would I want it? At the moment, RAM sticks are scattered randomly over the RAM connectors. >>
Mart, Interleaving memory is when you put two "same size" sticks in paired slots. For example, if you have two 32mb sticks, you'll possibly get 10-30% faster ram access when they're in slots A1 & B1, instead of A1 and A2, etc. This is a copy of parts of the thread. >Someone was asking about interleaving memory. According to NewerRAM's GURU >program, it says, "Can interleave memory for approximately 10-30% faster Ram >access". Now, from what I understand, it can theoretically do this because it >can read from one ram module in the pair while writing to the other module in >the pair when they are in paired slots. So, I wouldn't expect to see a real >increase in speed unless the program you are using was doing this. I've read >that SCSI drives are faster than IDE drives for the same kind of reason. SCSI >drives can do multiple requests,etc. whereas IDE drives have to finish one >request before going on to the next. However, I suspect most people wouldn't >see a real speed increase except under certain circumstances. > >HTH >STeve > > > I don't know if it's an accurate indicator, but Guage Pro does show a 10% increase in moving memory when I interleave in both my 7500/g3/250 and 9600/g4/450. and Actually, the PowerSurge machines are faster with interleaved RAM because of latency. Latency is the time delay between a read or write request and when the RAM actually delivers the goods. On the PowerSurge class machines, the HammerHead memory controller chip (343S1190) is tied to two completely separate memory banks, bank A and bank B. Each has their own Data Path (343S1141) controller chip. When Hammerhead detects that identical modules are present it interleaves memory accesses. So, a read comes in. Hammerhead sends the request to both Data Path controllers each of which controls a separate DIMM out of the interleaved pair. As soon as one Data Path controller finishes delivering the goods from RAM, the other delivers its stuff. While the second is delivering, the first is getting the next batch of data out of the memory sticks, etc. They go on trading off like this with Hammerhead waving baton to keep them coordinated. In affect, the PowerSurge machines have two separate sets of memory circuitry tied together by Hammerhead. Hence (I speculate) the chip name for the memory controller, Hammerhead. If you look at a block diagram, there's this big chip in the middle with a Data Path chip on either side just like a hammerhead and the other stuff (like CPU and PCI/Bandit) trailing off behind. and Interleaving causes both DIMMs in a pair to be read when data is needed by one of them. That way if the data in the second DIMM (occupying the subsequent memory position) IS needed then it is available immediately without have to wait for a memory access. So it shaves off some time in those cases where memory read is sequential. The most common case of sequential reads is from executing code and if it is part of a loop then it's likely this is in the cache already so interleaving only helps on the first pass through. HTH STeve -- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:pci-powermacs@;mail.maclaunch.com> To unsubscribe, email: <mailto:pci-powermacs-off@;mail.maclaunch.com> For digest mode, email: <mailto:pci-powermacs-digest@;mail.maclaunch.com> Subscription questions: <mailto:listmom@;lowendmac.com> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
