Juno board revisions

There are a number of key differences between each revision of the Juno platform, including hardware limitations. Some of these are documented on the official Juno product page, namely:

• Juno r1 onwards supports PCIe
• Juno r1's Cortex-A53 cores have a pinned operating frequency (fixed in r2)
• Newer revisions of Juno incorporate newer revisions of constituent IP (processors, CCI, NIC, etc)
  • For example Juno r2 replaces the Cortex-A57 cluster with a Cortex-A72 cluster
• Juno R2 has 2 variants: VarA & VarB
  • Juno R2 VarB boards have different DDR memory fitted compared to VarA and the previous board revisions. This is because the DDR memory previously used is no longer available.   The change of memory requires the SCP firmware to use different DDR controller settings to configure the memory correctly. The SCP firmware knows when to use the different DDR settings by looking at the variant information in the motherboard EEPROM. 

We strongly recommend that users always use the latest deliverables on their board.  This is especially true for users of Juno R2, as you may have variant B which is not supported by older firmware.

There are three ways to reliably determine which revision of the Juno you have:

1. Look at the main SoC
   • Juno r0 has: Cortex-A57 MP2 r0p0, Cortex-A53 MP4 r0p0
   • Juno r1 has: Cortex-A57 MP2 r1p1, Cortex-A53 MP4 r0p2
   • Juno r2 has: Cortex-A72 MP2 r0p0, Cortex-A53 MP4 r0p3

    

2. Remove the fan on the back-plate and inspect the motherboard where it sat
   • Juno r0 has: HPI0262B
   • Juno r1 has: HPI0262C
   • Juno r2 has: HPI0262D

    

3. Use software to query the V2M APB `SYS_ID' register
   • The register is at address 0x1C010000
   • Bits [31:28] hold the `Rev' field
     • Juno r0 has `Rev' == 0x1
     • Juno r1 has `Rev' == 0x2
     • Juno r2 has `Rev' == 0x3

NOTE: The board prints out the version and variant from the MCC on powerup.