# \#rabbit-5000

**URL:** https://forums.digi.com/tag/rabbit-5000/4480.md

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## [Rabbit 4000 cbm instruction - (de) operand without ioi or ioe?](https://forums.digi.com/t/rabbit-4000-cbm-instruction-de-operand-without-ioi-or-ioe/21980)

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**Author:** [@spth](https://forums.digi.com/u/spth)\
**Replies:** 1\
**Last updated:** [November 28, 2020, 9:10am UTC](https://forums.digi.com/t/rabbit-4000-cbm-instruction-de-operand-without-ioi-or-ioe/21980 "2020-11-28T09:10:31Z")

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The description of the Rabbit 4000 cbm instruction states calls (de) “address of I/O register” and states “only (de) is affected by ioi or ioe”. What happens if neither ioi or ioe is used? What will (de) refer to? Inter…

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## [How to tell the difference between Rabbit 4000, 5000 and 6000?](https://forums.digi.com/t/how-to-tell-the-difference-between-rabbit-4000-5000-and-6000/21810)

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**Author:** [@spth](https://forums.digi.com/u/spth)\
**Replies:** 2\
**Last updated:** [October 1, 2020, 3:07pm UTC](https://forums.digi.com/t/how-to-tell-the-difference-between-rabbit-4000-5000-and-6000/21810 "2020-10-01T15:07:58Z")

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The Rabbits have the GCPU and GREV registers. they allow to easily identify Rabbit 2000 and Rabbit 3000 variants (GCPU for the Rabbit 2000 vs. 3000, GCREV for the revision). However, according to the user manuals, the R…