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Reference SRAM block update
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marnovandermaas committed Jan 27, 2025
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Expand Up @@ -114,16 +114,16 @@ In CHERIoT Safe the size of the revocation tag memory is 16 KiB.
### List of SRAM blocks

Here's a list of blocks by size that we need to allocate in SRAM.
The XC7A35T has 100 blocks of 18 kilobit block RAM, [see datasheet](https://docs.xilinx.com/v/u/en-US/ds180_7Series_Overview).
In total that gives use 225 KiB of block RAM, but we may not efficiently map onto 18 kilobit blocks and thus lose some memory.
The block RAM usage in the table below was calculated using Vivado 2023.2's block memory generator.
The XC7A50T has 150 blocks of 18 kilobit block RAM, [see datasheet](https://docs.xilinx.com/v/u/en-US/ds180_7Series_Overview).
In total that gives use 337 KiB of block RAM, but we may not efficiently map onto 18 kilobit blocks and thus lose some memory.
The block RAM usage in the table below was calculated using Vivado 2024.1's block memory generator.:

| Type | Size | Width | Depth | RAM Blocks |
|------------------------|---------|-------|--------|------------|
| Internal memory | 128 KiB | 33 | 32,768 | 60 |
| Revocation tags | 16 KiB | 32 | 4,096 | 8 |
| RAM capability tags | 32 KiB | 32 | 8,192 | 15 |
| Revocation tags | 2 KiB | 32 | 512 | 1 |
| RAM capability tags | 36 KiB | 32 | 9,216 | 18 |
| Instruction cache data | 4 KiB | 64 | 512 | 2 |
| Instruction cache tags | 1 KiB | 22 | 512 | 1 |
| Total | 181 KiB | | | 86 |
| Available | 225 KiB | | | 100 |
| Total | 171 KiB | | | 82 |
| Available | 337 KiB | | | 150 |

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