VOGONS


First post, by lafoxxx

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Hi.
Is there any performance difference in using 1x512 MB SDRAM stick instead of 2x256 MB?
It's not DDR SDRAM.

Reply 1 of 8, by Tiido

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More chips = higher loading on the bus and that rounds out signal edges due to parasitic capacitances (most signals are parallel on the two sticks and on chips on either side of a stick and their capacitances add up) and that can result in worse stability at higher speeds if you plan to overclock. On one PIII board I cannot do 1GB due to this, my 512MB sticks have 16 chips each and 32 chips total is too much, same problem with 2x 256MB sticks with 16 chips on them, while pair of 256MB sticks with only 8 chips work fine or 512+256 giving 24 chips. One other board doesn't care at all though and any combination works fully.

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Reply 2 of 8, by pentiumspeed

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440BX no. (cannot use 8 chip 256MB).
815 or any newer chipsets that supports 8 chips memory works fine.

Cheers,

Great Northern aka Canada.

Reply 3 of 8, by alvaro84

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As said earlier, BX doesn't support 512MiB modules, only 16-chip 256MB ones. 815 and VIA 694 does, though.
In boards based on these chipsets a 16-chip (usually double sided) 512MiB module is basically equivalent to two 8-chip (usually single sided) 256MiB ones. Two 16-chip 256MiB modules put a higher load on the memory controller, though, possibly limiting overclocking or memory timings. I, for example, picked a bunch of memory modules that can run at 150MHz/cl2 in my P3B-F - but they don't necessarily do when I use more of them so picking a pair needed further testing. This is exactly because of the extra strain on the chipset.

Btw I've tried double stacked (32-chip) 1GiB modules in MSI 694T Pro and it worked fine though it would definitely cause problems with stock Win98. So I went with a single 512MiB stick and kept the "BX friendly" 16-chip 256MiB ones for the P3B-F and other older SDR boards.

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Reply 4 of 8, by dionb

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It's not just BX, most SDR-SDRAM memory controllers can handle max 128Mb chips so are limited to 256MB on a non-stacked DIMM.

But maybe OP should tell us what board he wants to use it on. For all we know now he might have an Aladdin 7 chipset with dual-channel SDR-SDRAM which would perform a lot better with two DIMMs...

Reply 6 of 8, by dionb

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lafoxxx wrote on 2020-05-10, 12:58:

The board is ASUS TUSL2-C, with Intel i815 chipset.

Then everything said earlier is applicable:

- 512MB should work
- 512MB will load the bus exactly the same as two 256MB DIMMs with 8 chips of 256Mb each.
- 512MB will load the bus less than two 256MB DIMMs with 16 chips of 128Mb each.

Reply 8 of 8, by dionb

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lafoxxx wrote on 2020-05-10, 22:35:

Thanks!
Turns out things are little more complicated than I thought for SDRAM.

Not really - this would apply equally (just with different numbers) to older FP or EDO or newer DDR(x) RAM, also per-channel in dual/tri/quad channel setups. You always have a max supported chip density, and the fewer chips there are in parallel on the bus, the lower the load, so the higher the headroom for stability (and/or overclocking).