The Z80's feature discovered after 40 years [video]

Re:The Z80's feature discovered after 40 years [video] by Starwatcher2001 on Monday October 17, 2022 @05:12AM (#33231294)

I did a lot of that on my CPC464 and TRS-80 too. Thanks for rekindling the memory. Relative jumps were the easiest way to make code relocatable, but you were limited to +/- 128 for an offset.

I used the "Programming the Z-80" book by Rodney Zaks, which is still on my bookshelf. Some manuals just can't be disposed of!

From memory I recall my favourite instruction - LDIR (Z80 block memory move) is EDB0, and JMP is CA.

Slightly more on topic, I piggybacked a 2716 EPROM onto the back of the TRS-80 ROM so I could get to the previous hard-coded RST locations and interrupt vector of the Z80 processor. In a nutshell, that allowed me to stop/debug/hack running programs without software being able to prevent me.

Fun times.

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Re:The Z80's feature discovered after 40 years [video] by jgrahamc on Monday October 17, 2022 @05:23AM (#33231367)

I used the "Programming the Z-80" book by Rodney Zaks

I have that and the 6502 book by Zaks also. I read those books when I was a teenager as if they were tomes filled with wisdom of the ancients. I protected them with plastic book covers and wrote my own notes in the margins in pencil. I worked a Saturday job when I was 16 and spent the money on them. At the time they were so expensive!

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Re:The Z80's feature discovered after 40 years [video] by davidgerard on Monday October 17, 2022 @06:18AM (#33231638)

same, protective plastic cover and all

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Re:The Z80's feature discovered after 40 years [video] by GeorgeTirebiter on Monday October 17, 2022 @02:08PM (#33237484)

Thanks you guys, now the eBay price for those chestnuts has likely doubled! ;-)

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Re:The Z80's feature discovered after 40 years [video] by abraae on Monday October 17, 2022 @01:10PM (#33236593)

Ditto, I've been purging my old tech books but I just couldn't let the Zaks book go.

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Re:The Z80's feature discovered after 40 years [video] by pmontra on Tuesday October 18, 2022 @04:56PM (#33253812)

Same plastic cover on Zaks' book (it's still there) and excellent paper quality.

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