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testing z80s....

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Unplug the built in one and plug in the one in question

if it boots and does all the usual stuff its a good Z80.

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Over the years the only Z80s I've seen that were bad

were either missing pins (obvious), or subjected to

significant over voltage.? In general it takes a lot

of mistreatment to kill one.? However people do

manage to do that.? Enough ESD and you can

blow up a pin, its input or output circuit on the die.

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More common this day and age is fake/fraud

marked parts that are not even z80.

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Allison

Hi Lee,

I am loving the Z80MC (thank you!), although so much to learn that is fine. Here are some suggestions for consideration (without altering the original art) :

1- Going back to 15K from 18K to resolve S8 button issue

2- Perhaps a micro piezo speaker

3- Instead of cutting one of the 10 pin connectors I used one of these black single row connectors. Much easier to cut and works fine.

4- If NVRAM is a viable option which I still couldn't figure out if it is plug and play (just like 1802 with super capacitor) or will require a lot of coding to work, nice to make it an option.

5- If there is room in the EPROM, some self test ROM/RAM capability accessed from the front panel would be great.

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*- I wonder if Z80MC can be used to test another external Z80 for NMOS/CMOS and full functionality

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Thank you and Best Regards,

Kerem

Yes, those days are now really old...? ;)

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I have a assortment of machines all speaking either CP/M or NS*DOS.

NS*DOS was a strange animal as it was basically bag and tag and tightly

bound to their hard sector controller.

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The worst part of hard sector was it was only compatible with

itself (or same brand) making portability not happening.? I had

to?add a soft sector controller 765 based? and a 8" drive to get

compatibility with the world as in SSSD 8" CP/M format.

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That said one of the more interesting things was to take the source

for NS*DOS and make it independent of the MDC controller.? The

result was a primitive file system but you could create directories

within directories.? It also was logical sector addressed and sector

size independant so that it could be 256 (original hard sector) or

512 (the double density version) or anything.??

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ISIS was another OS that was truly intel and strange.

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Most exciting to me was being able to tech the CP/M machine how

to read a RX01 (also SSSD8")? with RT filesystem (radix50 file names).

With that my CP/M crate to talk to the world of PDP11s and even

VAX/VMS machines that had floppy (RX06) or over the DECNET

Either pipe..

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Networking was easy I read a few papers and then

William? Wongs (microcomputing) and it was?then easy

if speed was not the major issue.?

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Most serial ports on s100 and similar could go fairly fast.? So

a protocol like?csma/cd at the physical level and then pile

stuff on it.? Only two signal lines signal and ground at

TTL levels.? I had easy interconnect wired into the BIOS

and 19.2 KB (faster always left a slow system behind).?

Proto networking between not less than 3 systems.

It would extend to 5 one being a LSI11/23 running

RT11.?

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Allison

Allison,

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Ah yes, the "good" old days. :-)

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My first disk system was a Heath H89 with a single H17 floppy. 40-track, hard-sectored, single-sided, single density, which stored 92k with CP/M. Operating with only one drive was tedious, but possible. Heath's clever BIOS created additional "phantom" disks (A: B: C: etc.) with one physical drive. So PIP B:=C:FILE.TXT would keep saying "put disk B in drive A and press Return" etc. as needed. Copying an entire disk was really slow. Lots of elbow exercise, but it worked!

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Later, I had an S-100 box with a Micromation "Doubler" and two SS Shugart SA801 8" drives, which stored 488k per disk. Then a Micromation "Doubler" and SD Sales "Versafloppy" controllers which put over 1 Mb on 8" floppies.

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Interestingly, my old 8" drives still all work, while most of my 5.25" drives are flakey, and the 3.5" drives are even worse.

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On networking: I have Woolf Software's "Move-It" program, which connects CP/M (and DOS) systems via their serial or parallel ports. Each box can see the other's drives. So A: B: C: are your local drives, and RA: RB: RC: are your remote drives. There was a DOS version as well, but I've lost it. That was my networking solution for many years.

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Lee

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--

Excellence does not require perfection. -- Henry James

But it *does* require attention to detail! -- Lee Hart

--

Lee A. Hart

Remap...

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Lets say drive B is a 8mb container file on some disk.

Elsewhere there are 124 more of them (1GB media).

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My box can make any of those 124 others appear as

drive B: same for C: and D:.??

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Mount is? CP/M program? written in BASIC that reads

a file DISK.DTA and that has all of the mappings

listed by name or a simple number (yet unnamed)

and what ones are active as? Drive letter.? I can

reassign B though C to any of those potential drives.

DISK.DTA is just a database.

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In use I boot nominal first 4 drives A: is always fixed for

sanity and also since all the mainline programs

( marked system) are there.??

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With that I can make C: into CLIB and D: into CPROG.

Or C: as PASLIB and D: PASCAL.? And so on.?

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It allows me to deal with the lack of hierarchical directories

in CP/M.

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The selected disk named are just? pointers to where that

"partition" starts on meda as everything else like size

are fixed.? So the only? parameter in the DPBlock is "offset"

as a variable.? ?That database also has information like

where it was before as in if B was CLIB and I change to

BASLIB it will have an entry listing what B was before.

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I was a VMS user and used to moving around directories?

as needed to organize projects and all.? ?Closest thing is the?

directory system of Linux.?

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Allison?

Lee,

My first system with disk was Altair box NS* disk and 48K ram

and that was 1977.? FYI the NS disk was Sa400 35 tracks,

10 hard sectors and the boot disk has about 81K of usable space.?

Since the altair backpland and from panel were on a good day

flakey and only got worse with Z80....

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Next system was Northstar Horizon crate.? Good backplane,

two serial ports, one parallel and 56K of ram and the NS* floppy

controller.? That would go from hard sector to softsector using

d765 and to 64K ram.? less than a year later St506 (5mb) and

soon after quantum D540 31mb. Boot was from eprom.

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Multiple generations later...

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The Compupro based in a new Northstar horizon box was

created to get the most possible out of CP/M.? It still lives.

That has many CPUs with slave cards and other smart

hardware support. by 1985 it had more resources than

the then average PC.

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Actually the whole 20 CP/M systems still live and work as?

desired.

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Needless to say there were many generations of BIOS to suit

hardware and support expanding ideas.? I did it to get

performance and avoiding the bag on the side 8088.

I managed to stay out of PC until the mid 90s networking

was the inflection point.

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Allison

Josh,

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You still? need a ap on your PC to read the CP/M directory in the container file.

so going direct is one step less.? If the one available works great.

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Fat with the container file fragmented (scatter gather) would be bad and

CP/M itself? has the scatter-gather in the file system.? So you can have a

literal double scatter.? ?That is unlikely as the FAT file is built as whatever

size on formatted media, delete it and write again all bets are off.

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Oddly in normal operation CP/M does more reads than writes.? Most

common is directory.? Second most common file loading.?

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Indeed it beats floppies hands down.? ?Ask me how i know... ;)??

Hint a very early adopter....

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Still baffled why anyone would? small container files (like 360K)??

Might as well all be 8mb for elbow room not as if it takes much of the uSD.

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Also what's missing is a way to remap any container file on the media?

to one of 4 drives.? CP/M allows that and I do that all the time on my

AmproLB+.? ?It allows me to use more of the larger disk without?

eating up the TPA for allocation tables.? ?Most of the systems

I've built are 4 logical drives (some 8 if the tables are in mapped

ram) with a mount utility to access other sections (containers)

on the larger disk on the fly.?

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Allison

makes sense since you'd probably otherwise need a special app on the PC side to read/write into the raw block store.

no urgency on any of that, of course; I happen to enjoy reading code.
yes, coincidentally I've seen your posts on QRPLabs; lol.

Josh Bensadon originally wrote the Z80MC's CP/M code for his JAIR board. It's a single-board S-100 computer with an 8080 CPU, 64k RAM, boot ROM, 2 serial, 3 parallel ports, and a parallel interface to an SD-card serving as its "disk" drive. He noted that the 2 MHz 8080 parallel interface was about the same speed as the 4 MHz Z80 with "bit banged" SD-card interface. So that's what we went with for the Z80-SIO.

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It's not as fast as modern hard drives, but is certainly faster than any floppy disk system I've had. CP/M programs also tend to be small, so disk read/write time is not nearly as important as you might expect.

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Josh used FAT16 so you could read/write/format the SD-card on a PC. It does slow down the Z80 to read the FAT16 directory structure instead of the simpler CP/M structure, but was a straightforward way to allow up to a 2 Gb disk.

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Lee

--

Excellence does not require perfection. -- Henry James

But it *does* require attention to detail! -- Lee Hart

--

Lee A. Hart

Dave,

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Code for direct sector access is currently only for CF (and IDE).? Since only two of

my machines are uSD I haven't gotten to it but the basic skeleton would based

off the CF versions with the device level interface and command protocols

being different.? ?For bit bang uSD that is a lot of code that is different but

it eliminates the code needed to find a directory and file under fat16.? The

read and write to a sector (physical 512) will be the same.

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The two sections of the BIOS impacted is (D=Disk) DREAD and DWRITE.

If I get that far I'd likely add large buffers in one of the unused 32K ram

banks.? And foreground background as I have systems with that built in

most common use is print spooling.

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As it stands the current code is very good and the TPA is large enough

to run most C compilers and screen editors.? I use BDS-C, BASCOM,

Mbasic, Pascal, assembler and macro assembler,?and Vedit.? Generally

save for screen specific code ( cursor and keyboard keys) if it runs

on Kaypro it runs on MC (using serial terminal).?

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Right now I'm spending more time on RF analog stuff (222 transverter,

432 power amp).? ?Lots of drilling and blasting (mechanical construction).

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Allison

Generally its better.

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Since the SPI interface is bit banged having to shuffle less means

less time doing bit bang to move stuff.? Think in terms of layers.

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Code may be smaller as well, less code executed is faster.

However the BIOS changes!??

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To date I only have two systems with uSD the z80MC and

SC131 (20mhz z180).? Note the Z180 uses the SPI interface on chip

so speed is very fast.? The rest of my systems are IDE one

with spinning media and two with CF (CF is byte parallel, faster).

The rest of my 8085/z80 systems have MFM-hard disks D540

31mb (spinning rust) and intelligent controllers.? I have over

20 CP/M systems of various designs and performance levels

many running BIOS I had to build.? Of those 5 are S100 crates.

Most portable of the is the Epsom PX-8s laptops I have.

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Me, been using CP/M since '76 and did V1.3, 1.4, and usually V2.x.

I also use PCP/M variant and Zrdos enhanced CP/M clones.? The

clones are structurally similar but add features like logical devices

larger than 8MB as the internal math is more complex and can

directly address 1GB.? Only one comment is that big devices

have big flat directories that take forever to search.? CP/M

does not hierarchical directories.? So partitioning devices to

smaller 8MB is the general way.

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I also write code for CP/M but also have modified CP/M internally

and run with ZCCP replacement for CCP.? ?For the non-CP/M fluent

the CCP is the command line processor, Bdos is the base logical

Filesystem and IO, the BIOS is the layer that does logical abstraction

to physical for IO and mass storage.

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CP/M discussion are based on logical devices and physical.? For

example logical sector is always 128 bytes.? Physical can be anything

that is usually device inherent (IDE, CF, uSD that's 512bytes).??

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A must have is the entire CP/M manual set (many thin manuals

or one thicker book) as they pretty much give the whole of

required information on use and modification.

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I speak PDP-8, 8080,8085,Z80, fluently and passable conversations in

1802, TI9900 , PDP-11 and solder (hardware).

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Allison

That's super interesting. ?I wonder what the numbers are on the Z80MC for the elimination of the FAT layer relative to direct block I/O. ?I would guess that a majority of the time is spent in the bit-banged SPI, which might swamp out the benefits, but you never know until you measure... ?(and maybe ram/rom savings alone makes it worth it).

Anyway, if you have code, I wouldn't mind seeing it. ?I am Z80 competent, but a CP/M dilettante, so I'm sure I would have knumbskull questions.

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-dave

Unless the system has a real floppy I do not bother with smaller

disk formats.?

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When you use CP/M larger disks makes life easier as anything

under 500K can get cramped fast or force spreading out across

multiple drives.? Assembling CP/M (CCPand BDOS) from source?

on a 8" 241K disks needed three drives source on A: and output

to B: and C: even then it was cramped.? The resulting new version

with new bios and FDC that could support double density two

sided on the 8" drives 1020k system, usability and speed improved.

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Allison

Thats it!? That dang DLL, easy to find and install.

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Myself I do large devices and I don't do from container files in

Fat file systems.

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My approach is format the uSD or CF as fat.? Then use parted(linux) or

other tool discover where the device Block replacement table

that is used internally.

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The system treats any foreign format as meaningless.? ?The BIOS I've

done treat CF or uSD as a contiguous collection of 512 byte blocks

addressed as LBA.? Usually starting at 1000h and for every 16384

(0x4000)blocks are a? 8mb disk.? The parameter block in the bios

has a parameter called offset by making sequential logical drives

easy to do on large devices.? ?No need to partition the device.

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One trick I've started to use is make the first block in a non file space

a format table so I can move the device to another system

(mostly IDE/CF).? It describes size and organization.? A single

block is easy to read and understand than a partition table.

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Using FAT16 to do this works but adds another layer of?file system?

to find the desired container files and its starting address or

extended address.? Adds overhead and makes the device

readable by PC save for the file contents still needs a tool

to understand the CP/M directory structure.? A similar tool

could easily read the device directly without using FAT.

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Actually I have tools for CP/M that can write RX01 (RT11 format)

and DOS fat12 or fat16 floppies and write them as well.

I found that more convenient when floppies were a thing.

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Allison

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; the 250 KiB format for Z80MC
diskdef z80mc0
? seclen 128
? tracks 77
? sectrk 26
? blocksize 1024
? maxdir 64
? skew 0
? boottrk 2
? os 2.2
end

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; the 8 MiB format for Z80MC
diskdef z80mc1
? seclen 128
? tracks 1024
? sectrk 64
? blocksize 2048
? maxdir 1024
? skew 0
? boottrk 2
? os 2.2
end

cpmls -f z80mc0 DAVEDISK.BIN

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cpmrm -f z80mc0 DAVEDISK.BIN CPMTEST.COM

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cpmcp -f z80mc0 DAVEDISK.BIN cpmtest000.bin 0:CPMTEST.COM

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I wanted to but, it would have been 600 miles round trip and?

I'd not be able to stay over night.? Maybe next time.

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Last time I was down there was about 1980 when it was

TCF Trenton Computer Fest.

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Hope it was good for you.

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Allison