Is anyone interested with the Z80?

I assume you mean Bletchley Park?  Not sure what was at TnMOC when you last came, but the Bombe is up and running in its new home with daily access - Tuesdays are engineering day so it may not always be running that day but you can still visit and get an explanation.  There is also an Enigma machine to support the demo.  EDSAC is pretty much done and going through its final tweaks: it can run a program but still some minor issues to resolve.  The Harwell Dekatron (WITCH) is in place and that’s a fascinating machine to watch, especially its decimal storage.  And of course Colossus, Tunny and Heath Robinson, the air traffic control display and all the 1980’s home computing machines you can play on - who remembers Manic Miner?

At the moment the roof is being replaced and the large systems gallery is closed so you can’t see EDSAC or the WITCH (or the ICL and other large systems). Check the website for when that work is finished.

I've not been since the separation from the war museum, I suspect it's changed a bit since I was last there.

I'm not deeply into the Z80 these days (apart from just general interest since it was the CPU in my first home computer), but there are some Z80 reference books here, although you've probably already got them or equivalent info:

Index of /components/zilog/z80

That site is great in general for all sorts of retro stuff from different manufacturers.

Many thanks for the offer but it's a little hard to pop in from Australia.

Are you able to take a photo instead of a list?

When I went to Bletchley Park a few years ago the Museum was closed.

I volunteer at The National Museum of Computing in Bletchley (Milton Keynes).  For anyone who is interested, can move fast, and happy to donate to the museum, we have a ton of z80, 6502, Spectrum, ZX81, Commodore etc books we want rid of.  No lists, you’d have to visit.  It’s a good library to do some research into old machines.

For Specy fans, some interesting books

If anyone is playing with Z80s and CP/m be aware that Microsoft BASIC Compiler is only marginally faster than its interpreter sister.

The BASCOM and interpreter are 8080 based programs that are not optimised for the Z80.

From what I have experienced, the compiling a BASIC program results in a huge binary file that consists of the user's original BASIC program with keywords/tokens replaced with generic machine code mechanisms that call up rather large runtime library.

A simple (but fantastic) game like LADDER ends up being 40K in size when its Z80 counterpart is magnitudes smaller and efficient.

G'day Bob!

Yep, the Z80 has 3 interrupt modes.

IM0, IM1 and IM2.

IM0 (Interrupt Mode 0) is exactly the same as the 8080 where the interrupting device places a CPU instruction on the data bus during an Interrupt Acknowledge cycle. This instruction is usually a singly byte RST instruction but  can be any instruction one wishes. Not often implemented by hobbyists due to the additional hardware involved.

IM1 (Interrupt Mode 1) is just a simple RST 0038.  When and interrupt is asserted the CPU calls the routine at memory address 0038H.

IM2 (Interrupt Mode 2) is popular for hardware designs with Z80 peripherals such as the PIO or CTC are present. To get this working, the programmer must firstly set the CPU's I (Interrupt Register) as the Page number (i.e. the most significant byte) of where the nominated 16-bit Interrupt Service Routine addresses will be placed, secondly configure the supporting peripherals to generate the required interrupt vector (i.e. the least significant byte of the address) to fetch the ISR address, and of course execute IM2 and EI (Enable Interrupt) instructions.

Upon exit from an ISR it is usual to perform an EI, RETI combination.  The Z80 is configured so that the EI instruction does not become effective until the completion of the following (usually a RETI or RET) instruction.

However nested prioritised interrupts can be supported with the insertion of EI, NOP instructions at the beginning of ISRs but appropriate management is required to ensure correct operation.

Milton Feng and Walid Hafez have an experimental BJT working at 605GHz. IBM and AMD claimed to have switching transistors as fast as 2.0-3.3TeraHertz.

At that speed I wonder how they'll dissipate the heat and everything would have to be soo close together to work.

It is what I was thinking reading this. Maybe I can plan to put this topic in one of my next articles. But it is possible that when I can do this Z89 is no longer in production

Enrico