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1GB PC133 modules -- did they happen?

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First post, by lepidotós

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I'm looking for 1GB modules -- not 512MB pairs. ECC is fine; I'm getting them for my Power Macs.
As you may know, the G4 Digital Audio brought the number of slots down from 4 to 3, and thus the max RAM down to 1.5GB from the previous 2, and that wouldn't be reversed until the MDD which was based off the Xserve rather than the previous Power Macs, and I'd like to see if it's just a physical difference and I can get back up to the 2GB max of the Sawtooth and Gigabit Ethernet models on my Quicksilver, or if the memory manager can't handle 2GB.
I remember hearing 1GB SODIMMs weren't in spec for either PC133 or DDR1, can't remember which, but they may have existed anyway for edge cases so I'm wondering if 1GB full size modules were ever made -- and if so, where I could find at least one. I tried once already, but the modules I bought ended up being 278-pin PC120.

Last edited by lepidotós on 2022-02-10, 02:44. Edited 1 time in total.

Reply 3 of 9, by snufkin

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Well, some (most, I think) registered PC100/133 SDRAM sticks can be converted to unregistered, but the motherboard may not support the full capacity due to missing address lines: Re: Converted registered SDRAM

Turns out registered sticks use pin 147 as a register enable (REGE) pin. Pull that to ground and the signals are no longer registered, but are still buffered.

Reply 5 of 9, by snufkin

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One thing that might be worth checking is whether pin 126 is connected between slots and if you can see a trace going towards the chipset. That's the A12 line, which I think would be needed for 1GB sticks. The motherboard that was being tested toward the end of that thread about converting registered to unregistered didn't have A12 routed and only saw 512MB.

Based on: Row Address A0-12, Column Address A0-A9,A11 (A10 is auto-precharge signal), Bank Address BA0-1, and Chip Select = 2^13 * 2^11 * 2^2 * 2^1 = 2^27 = 128Mi possible addresses. 8 bytes per address = 1GiB.

Reply 7 of 9, by lepidotós

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Okay, so I have both the Quicksilver and the 1GB DIMM -- and nothing. It doesn't recognize it at all. The slot works, the included 256MB stick reads just fine.
I'll check pin 126.

Reply 8 of 9, by snufkin

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Which DIMM did you get? It's possible that Apple actually check the SPD on the stick and then just refuses to use it if it's out of spec, so you don't even get half the capacity. I thought I was going to have to edit the SPD when I was trying to convert a registered stick to unregistered, but the BIOS on my KA7 didn't care. When Sphere478 tried a converted 1GB stick on a board with an Ali Aladdin V chipset then it just counted to 512MB, and it looks like A12 wasn't routed out from the 1542.

Reply 9 of 9, by lepidotós

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The only branding on it says "MemoryMasters 1GB SDRAM PC133 3RD". Here's the listing I got it from: https://www.ebay.com/itm/1GB-RAM-MEMORY-ROLAN … R-/171437401599

If they do check, they started checking after 1999, since my Lombard sees my 512MB stick as 256MB and uses it fine otherwise.

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