Is anyone interested with the Z80?

Did you know that the Z80 has different memory access timings for instruction fetches and standard memory accesses?

Did you know that the Z80 has different memory access timings for instruction fetches and standard memory accesses?

No, can you site a URL to see?

http://www.zilog.com/docs/z80/um0080.pdf

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I worked at Mostek maintaining the Fairchild Sentry testers used to test the Z80s when they first began to manufacturer them. The second computer I every

built (parts, pcb, solder) was the SDB-80 which was the Mostek Software Development Board for the Z80 with 16K bytes (8 - MK4116 16K bit) dynamic RAMs

which Mostek also made. The first wire wrap board I ever made was a 48K byte dynamic RAM board also using MK4116s that worked with the SDB-80. I can

tell you there were a bunch of happy technicians when we were told that Mostek would be second sourcing the Z-80 and even happier when we were told we

could buy SDB-80 kits and build them ourselves! Those were really fun days. I still have a Zilog Z80 in a ceramic package that says it was manufactured in

Dallas even though Mostek was actually in Carrollton a suburb in Dallas County just north of north-west Dallas.

Are you still in the Dallas area. So am I.

Clem

Wow! that's amazing that you got such a large DRAM board working with Wire-wrap.

Do you still have any photos or schematics of it?

It was quite rare to come across Mostek parts in Australia. We usually got Zilog, SGS and Sharp.

And from memory the SGS parts didn't support the undocumented instructions.

Yep, lived here all my life (more years than I want to admit to).

No photos but the schematics were from a Mostek Z80 application note which I may still have. I used a tool from Vector called the Slit and Wrap which used

small spool of wire coated with a soft insulator kind of like magnet wire that was slit by the wrap bit just before it was wrapped on the post. It was a great tool

for speeding up wire wrapping with one fatal flaw. If two wires pressed against each other hard enough, they could displace the soft insulator and short.

When ever I powered it up and it did not work I would have to look for two wires pressed against each other in a rats nest of wires (actually I was more

systematic than that but there were always problem areas) and separate them. When the offending wires were separated it would usually make a distinctive

"plink" sound so I knew when I found it.

I used the same tool and a Z80 to wrap up a 256 x 240 x 4 bit/pixel graphics display controller. The schematic was from Byte Magazine and I modified it from

the original 1 bit/pixel configuration and to use static RAMs that were fast enough to allow the Z80 full speed access to the video RAM by interleaving the

accesses with video timing generator. The Z80 assembly language software had to be entered in by hand to be assembled and of course modified to handle

the multi-bit/pixel mod and to use a 8 bit parallel interface to the SDB-80. I believe it only had commands for pixel read/write, line and circle drawing.

Unfortunately after quite a few sessions of find the Slit and Wrap short I gave up and disassembled it for the parts and never used my Slit and Wrap again.

Like I said, fun (and sometimes frustrating) days.

Ahhh!

The days of triple power supplies (+5, +12 and -12V).

Slit-N-Wrap from Vector.

It's still available today but not on the e14 catalogue.

I used a competing product called JUST WRAP and I think I've still got the blighter!

Yes, three voltage power supplies ruled then. And you can add +24V for the 8" floppy drives but they were usually in their own case with a separate

+5V, +24V power supply. The MK4116, and all other dynamic RAMs of the time used +5V, +12V, -5V which was usually derived from the -12V which

came in handy for  RS-232RS-232 drivers

I thought it was Slit-N-Wrap but I couldn't remember so I went for the long version. I thought Vector was still around, I wonder if they fixed the shorting

problem ?

I remember the Just Wrap too and I know I was very interested but for some reason, lost in the mists of time, I never bought one which is made even

more curious after all the Slit-N Wrap problems. I think I just went to pre-cut wire wrap wire (which I still cut to length) with an electric wire wrap tool but ...

I still have a motorized Slit-N-Wrap and I still use it once in a while. It used to be really fast for wiring low-speed backplanes - much faster than manually soldering connectors on PCBs. I built a circuit that would make it automatically stop wrapping after 7 turns.

I never had problems with shorts. They have 2 types of wire, one with a Tefzel (Teflon) jacket that is thicker than normal Kynar, the other is  a thin green enamel coating (a bit like magnet wire). I never had problems with either type although I was always careful not to let the green stuff rub on square pins.