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First post, by Private_Ops

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Looking at a video card (supposedly an Nvidia TNT 8MB).

Has 8 SGRAM chips, their data sheet shows "256K x 32 x 2". So, two banks of 256K.

https://www.digchip.com/datasheets/parts/data … 512A-8Q-pdf.php

Simple multiplication doesn't work here unless I'm not converting something correctly. So how do these 8 chips add up to 8mb.. or whatever they add up to.

Reply 1 of 5, by Zup

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256K --> Number of words in each chip
32 --> Size of word in bits (data bus width)
2 --> Number of banks?

So the banks have 256K addresses of 32 bits each (4 bytes) and sums 1Mb of RAM per bank. I don't know what does it means the bank thing... maybe they have 2Mb available per chip at every time, so you'll end up having 16Mb in 8 chips.

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Reply 2 of 5, by konc

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Exactly what Zup wrote, these chips as per the datasheet should be 2MB each (2 banks of 1MB).

Reply 3 of 5, by Private_Ops

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Ok, so it should be 16mb.

But how does 256K x 2 turn into 2 MegaBytes.

I'm missing something in translation here.

Reply 4 of 5, by konc

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You wrote it yourself correctly initially and Zup also explained it, it's not just 256K x 2 (where are the bits of each word in this?), it's 256K words x 32bit each word x 2 banks.

Let's break it down:
256000 x 32bits = 8192000 bits
8192000 bits / 8 = 1024000 bytes
1024000 bytes x 2 banks = 2MB per chip

Just guessing here, K stands for 1000 and not Kilobytes or anything similar. Like we often write Win2K

Reply 5 of 5, by Private_Ops

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konc wrote on 2022-09-07, 12:26:
You wrote it yourself correctly initially and Zup also explained it, it's not just 256K x 2 (where are the bits of each word in […]
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You wrote it yourself correctly initially and Zup also explained it, it's not just 256K x 2 (where are the bits of each word in this?), it's 256K words x 32bit each word x 2 banks.

Let's break it down:
256000 x 32bits = 8192000 bits
8192000 bits / 8 = 1024000 bytes
1024000 bytes x 2 banks = 2MB per chip

Just guessing here, K stands for 1000 and not Kilobytes or anything similar. Like we often write Win2K

Ah, the bits to bytes. That was the part I was missing.