EaZy80, A Simple80 with KIO

[Bill Shen]

EaZy80 was designed around the same time as Simple80 in 2019 and based on the same concept of glue-less Z80 SBC, but it was based on KIO (Z84C90).  The pc board was fabricated in 2019 but never assembled and powered on until today.  A number of critical signals controlling the RAM and flash were not even connected, so I probably didn't have a good idea of how to power up the board at the time.  Simple80 concept is now proven, so I can transfer Simple80 design to EaZy80 and benefited by the more robust I/O and faster KIO.  20+MHz EaZy80 should be possible with the fast KIO.  With more control lines from KIO, it can have 512K RAM with eight banks of 64K.  I don't know whether RomWBW can be ported to such hardware.

Right now EaZy80 CPU clock is 7.37MHz.  I was successful bring up the board using Simple80 monitor with few minor changes.  With the addition of a CF board, I expect it will run CP/M and enhanced HiTech C like Simple80 but faster.
  Bill

[Mark T]

Maybe if the pio outputs in bidirectional mode can be tristated by A15, then you could have 16 x 32k pages of ram with the top 32k common. Not sure if the pio could be used like this.

[Bill Shen]

Yea, maybe it has some kinda handshake mechanism like 82C55 that can be used for this purpose...

[Alan Cox]

Mux also works. How my 8085 MMU works. A16 up are from the mux and the mux inputs are 8 latched bits. The mux select itself can then be A15 or some other combo like A15 and A14 to get a nicer layout or jumpered. Was common in S100 days to have jumpered common size and top or bottom so you could run different OS as some wanted common low and some only needed 1K common 63K TPA

Alan

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[Bill Shen]

A 7432 2-input OR also works, but I'm still hoping for zero-glue logic approach.  KIO has enough I/O to bit-bang SPI for SD card, so I'm hopeful it can run CP/M without glue.

Did a quick overclocking test; the RAM is AS6C1008-55, so it should be the speed bottleneck limiting the CPU clock to about 18MHz, by the databook.  Well, it ran memory diagnostic fine up to 33MHz and crashed at 34.5MHz.  When I replaced the RAM with 25nS part, it still crashed at 34.5MHz, so I don't think RAM is the bottleneck.  My previous overclocking tests have indicated Z80 is limited to around 33MHz.

[Alan Cox]

On Sat, 18 Nov 2023 at 12:51, Bill Shen <coinst...@gmail.com> wrote:
>
> A 7432 2-input OR also works, but I'm still hoping for zero-glue logic approach. KIO has enough I/O to bit-bang SPI for SD card, so I'm hopeful it can run CP/M without glue.

The advantage of using the mux instead of a 7432 is that it's still
the same number of devices but you get both the 32K fixed behaviour
and the ability to switch upper 32K only (so you can run stuff like
ISIS) or indeed all 64K, making it useful for more applications.

With CP/M 2.2 it's fairly easy to use the extra memory for ramdisc
even in the case you swap all 64K providing you've got a way to get
something into multiple banks initially (eg the Simple80 CP/M I did
does it via ROM as does the SC10x CP/M version I run).

Alan

[Bill Shen]

EaZy80 monitor copies a number of bank-sharing routines to both banks of memory so it can move data between banks.  These are Ladislau Szilagyi's routines for Simple80 to use enhanced HiTech C and TE editor.

RomWBW at 30+MHz is just too tempting, so I probably will have an option for a TTL device to support 512K RomWBW.  Maybe I'll put it under the RAM so the board still LOOKED glue-less ;-)

I've tweaked Simple80's CP/M22 BIOS and loaded zexall in RAM to run Z80 instruction tests at 33MHz.  It crashed after the first test, so I'm repeating the tests at 31.3MHz right now.  It is running well, finishing the test in 25 minutes.  

So I'm calling it good as a neo-retro 30MHz, glue-less, CP/M Z80 SBC.
  Bill

[Bill Shen]

This is EaZy80 with Simple80's CF interface board.  CP/M2.2 is ported to it.

Created a homepage for rev0 pcb of EaZy80.

I'll see whether I can port RomWBW to it...
  Bill

[Bill Shen]

This is rev1 of Eazy80 with all the known engineering changes corrected.  It is functionally same as rev0 of Eazy80.  I've created a homepage for rev1 pcb with gerber artwork uploaded so if you are interested, you can order it from JLCPCB or other board houses.

I contacted the seller of Simple80 and ask him about a kit for Eazy80 (I have no financial interests in these kits).  He came up with a Z80/RAM/flash/KIO kit for $7.50 plus $5 shipping which is better price than Simple80.  I ordered 2 kits and will report back how they worked out.  

The board has a prototype area for experimentation.  KIO has so many I/O pins that I don't know what to do with, so the prototype area may be used to check out KIO functions.  One function I definitely want to try is interface to a SD disk to provide CP/M capability.

A hidden feature is under the RAM chip.  It is an uncommitted 14-pin DIP.  The idea is to install 512K RAM and wire in 4 bank selects through a quad OR gates (7432) to enable RomWBW.  In that configuration it is no longer glueless, but RomWBW is worth it.
  Bill

[Dave White]

Cool! Just ordered a couple of kits from the seller too.

[Bill Shen]

Good!  KIO runs faster, has more features than SIO and no more expensive.  The problem is KIO has too many features, I don't know what to bring out!  The seller says his Z80 and KIO are rated 10MHz, they are likely faster.
  Bill

[Alan Cox]

On Thu, 11 Jan 2024 at 01:11, Bill Shen <coinst...@gmail.com> wrote:
>
> Good! KIO runs faster, has more features than SIO and no more expensive. The problem is KIO has too many features, I don't know what to bring out! The seller says his Z80 and KIO are rated 10MHz, they are likely faster.

The problem with the KIO I always had is there are not enough I/O pins on it...

4 outputs for memory banking (preferably more to do 48/16 and 32/32),
5 for dual SD card, 2 for PS/2 keyboard
2 inputs for dual SD (to do it without glue), 2 for PS/2 keyboard, 5
for joystick
8 outputs 1 input for a printer port
15 I/O pins for CF
2 pairs of RTS/CTS

already run out by miles

Likewise 4 ctc channels you need two for the SIO leaving two for
interval timing but really they need chaining or you can take a fast
interrupt to get a sound channel, whereas a couple would be nice.

Maybe dual KIO is needed 8)

Alan

[Bill Shen]

I received the 2 Eazy80 kits in the mail today.  They looked good.  The date code on flash, RAM, and KIO are different so they are likely the original parts.  Both Z80 have the same date code, 0023, which I've seen previously with other "used" Z80 so they are probably re-labelled parts.

I already have two Eazy80 boards built up earlier; I programmed the flash without any problem, populated the boards and booted up with 7.37MHz clock.  Both boards booted without problems and passed memory diagnostic.

70nS RAM is likely the slowest part in the kits, but should run at 14.7MHz and they did.  Now going higher, 18.4, 20, 22MHz all working, but failed memory diagnostic at 25MHz.  22MHz is the top speed, most likely due to 70nS RAM which is working like a 50nS RAM with Z80 at 22MHz.

To further test Eazy80 at 22MHz, I loaded up cpm22 and ran zexall.com instruction test.  Both boards passed at 22MHz.  Power consumption while running zexall is 12...@5.0V.  

Good, I'm satisfy the Eazy80 kits are good.  it is a good deal at $7.50 plus $5 shipping. In my case it was 2 kits for $15 plus $5.50 shipping.  Disclaimer, I have no financial conflict with the seller.

Now I'm going to ask Alan Cox to help me with bit-bang SD card with KIO and make this into a glue-less CP/M computer.
  Bill

[Bill Shen]

An Update, I replacing the 70nS RAM with 25nS RAM on 32pin DIP carrier.  It booted at 34.5MHz, but failed ZEXALL.  I replaced with 33MHz and successfully ran ZEXALL in 23.5 minutes.  Current consumption for the board is 140mA, 5.0V.
  Bill

[Paul dB]

Very interesting! I was going to ask about putting a faster RAM on a 32pin DIP carrier to get past the speed barrier as I've just received Bill's DIP carrier boards from JLCPCB. I've also got EaZy80 boards and a couple of IC kits on the way 8).

Bill, which 25nS RAM chips are you using? I'd like to order a few.

BTW, this would be a good first step into SMD soldering; messing it up would just sacrifice a DIP carrier. Take another from the batch and try again!

Thanks,

Paul

[Stefan V. Pantazi]

Hi Bill,

Thank you for sharing. For the overclocking tests, did you use the 10MHz CPU that was sent? Or did you replace with a 20 Mhz part? I have been busy testing a batch of 20 Mhz Z80 CPUs and found none (other than a completely dead chip) that did did not pass zexall at 25 Mhz on Z80All. The only discernible differences between them seem to be related to the reset. Some behave differently at power on vs. button reset. My guess is that this due to small electrical differences between the parts, maybe the reset supervisor threshold, etc.

Stefan

[Bill Shen]

Paul, I used CY7C109-25VC which is SOJ32 package.  It fits the carrier board perfectly as shown in the photo.

Stefan, I used all parts from seller for the overclock tests which worked up to 22MHz.  For 33MHz overclock test, I only replaced the original 70nS RAM with CY7C109-25V on DIP32 carrier board.  

CMOS Z80, regardless of labeling, should work at 25MHz (this is why Z80ALL is 25MHz).  Most of them will work at 29.5MHz and some of them will work up to 33MHz.  It turns out KIO also works at much higher frequency than its rated frequency.
  Bill

[Paul dB]

Hi Bill,

Thanks for the info, but I was a bit too hasty; the carrier boards I had made were your PLCC32-to-DIP32 adapter boards.

Did you make the SOJ32-to-DIP32 carrier boards yourself? I looked through your projects but couldn't find these.

Paul

[Bill Shen]

Paul,
I was about to point you to my adapter homepages where I have quite a number of adapters designed over the years and realized I've never published them!  Well, I need to do that, but in the meantime this is the design file for SOJ32-to-DIP32 adapter.  It is only one board per design, I usually do a step-and-repeat to put 10 of them on a 100mmX100mm and send them to Seeeds Studio for fabrication because Seeeds does not charge extra.
  Bill

[Paul dB]

Thanks Bill, I've just put in an order for 5 adapters at JLCPCB.

Paul

[Bill Shen]

Returning to Eazy80 after almost a year hiatus.  I want to replace the 128K RAM with 512K RAM and port RomWBW to it.
 
First I wired a 74HCT32 quad OR gate to the uncommitted 14-pin DIP under the RAM, that control 16 banks of RAM with KIO's PC1, PC2, PC3, and PC6 outputs.  That worked OK, so now I have 512K RAM accessible as 16 banks of 32K memory.
Then I modified HBIOS's memory manager that'll work with the new bank switching hardware and generated a version of RomWBW that contained 256K of RAMdisk.
Lastly I added a SD card bitbang via PIO discretes, so now RomWBW has 8 slices on the SD card.

Here is screen capture of RomWBW booting up and accessing SD card.  Pictures of component side of Eazy80_512K and solder side of Eazy80-512K.

I'm not done; I need to come up with a RTC routine for RomWBW that bit-bang DS1302 using PIO; and I need a monitor command that boot RomWBW system file from SD card.
Bill

[pakt...@gmail.com]

Nice.

Easy80 and K80W are quite similar projects. Will you be consolidating K80W into Easy80 or will it continue as separate project?

If Easy80 will be able to boot from an SD card, then the CF card interface becomes optional. Adding at least one RCBus connector, a regular CF card module could be used (but, IIRC, the CF card device I/O address would need to be changed).

The RTC is nice to have, apart from showing the time, for reporting the CPU speed when you can't remember what oscillator is installed ;-)

Paul

[pakt...@gmail.com]

I forgot to mention that the eBay seller of the Simple80/Easy80 kits also has the PLCC version of Z80 should space be a premium.
Paul

[Wayne Warthen]

Looks great Bill!

-Wayne

[Bill Shen]

Eazy80 started from the cheap $7.50 kit on ebay and the desire to have zero-glue logic Z80-CP/M design.  The current development is a variation of Eazy80, where I added the 74hct32 gate and 512k RAM to enable RomWBW, but that pretty much marks the end of its development.  I plan to revise Eazy80 pc board to have the option of 512K RAM and SD card interface.  The large prototype area will be preserved because I want to explore various functions of KIO.  Eazy80 will remain an inexpensive experimental computer that’s cheap and easy to build.  BTW, the $7.50 eazy80 kit is still available on eBay.

I see K80W as a classic Z80 for RomWBW with 512K ROM and RAM and many features that RomWBW supported such as CF disk, SD card, I2C, RTC, video/keyboard, and RC2014 expansion slots.  It’s CPU clock is independent from IO clock, so it is a good platform to check out traditional RC2014 expansion cards.  Its downside is the CPLD which is difficult to find.

PLCC version of Z80 is more expensive, but in my experience it is always CMOS Z80 and capable of 25Mhz or faster operation.

Bill

[pakt...@gmail.com]

Hi Bill,

Have you had a chance to work on K80W? Were you able to boot from SD?

Looking forward to the finished board!

Thanks,

Paul

[Bill Shen]

 I have added a command to Eazy80 monitor so it can copy RomWBW system file stored in the SD card and boot into RomWBW.  Because SD interface is bit-banging, the transfer rate is only about 30KB/sec.  I have limited the system file copying to the first 128KB to speed up the booting time to about 5 seconds.  The RAM disk on drive A of RomWBW is blank, but there are valid files in drive B to drive I.  More details are here: https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:eazy80:eazy80r1pcb:eazy80r1home#eazy80_modifications_for_romwbw

I plan to update Eazy80 pc board to include SD card and enable the RomWBW feature with jumpers..

Bill

[pakt...@gmail.com]

Bill, thanks for the update on EaZy80. As I've got some extra boards, I'll try making the engineering changes to get RomWBW and SD working
with EaZy80.

BTW, did you notice the strange hiccup on your Tera Term printout, at the point where FD: is detected? Instead of printing the '0' (after 0x5),
there is what looks like a LF, and then 'NOT PRESENT' is printed.

Regarding my previous post about K80W, I think that wasn't exactly OT; I'll post my questions in a separate topic.

Thanks,
Paul

[Bill Shen]

Paul,
The "strange hiccup" where FD is detected has to do with KIO's I/O addresses overlap that of FD I/O.  Eazy80's KIO occupies I/O addresses $0-$7F which clash with many RomWBW supported devices, so I need disable FD to turn off autodetect.  Once that's done, the "strange hiccup" is gone.

In your previous post, I thought you meant Eazy80 when you mentioned K80W, so I didn't respond to your K80W question.  Anyway, since I've not worked on K80W in the last few weeks, I don't have any progress there.
  Bill

[pakt...@gmail.com]

Gotcha. There are only so many hours in a day ... or should I say only so *few* 8/
Paul

[Bill Shen]

While K80W has more features plus its lightening fast CF interface, I still find its poor cousin, Eazy80, more interesting.  This may due to its simpler design, lower cost and slower yet adequate SD interface.  Having a prototype area to explore many possible uses of KIO is particularly attractive.  Along with revision of K80W that I published today, I've also revised Eazy80 to rev2 to correct all known bodges.  Over the holiday I've built up a board and checked out the new revision.  I've also tested it OK to 22MHz despite the KIO and Z80 are marked as 10MHz part.
Bill

[pakt...@gmail.com]

Biil, thanks for publishing the revisions to both K80W and Eazy80. Much appeciated!

I noticed that you didn't include links to the revisions, so I'll include them here:

K80W Rev2.1, A RomWBW-capable Z80 SBC

Eazy80-512 For RomWBW

Also, on the project pages, the 'Schematic of Eazy80 for 512K RomWBW' is missing as well as the 'Bill of materials' for both boards.

Thanks again,
Paul

[Bill Shen]

Paul,
Thanks for including the links to latest revisions of K80W and Eazy80.  K80W rev2.1 artwork was a minor tweak and I published it without getting a board made first.  Afterward I did send in rev2.1 design to JLCPCB and I should receive the pc board tomorrow.  This way I'll have an accurate photograph for rev2.1 homepage.  Beside adding the missing ground trace, I also removed the "I2C" silkscreen (between CF connector and Z80) because the I2C design didn't work, but I kept the original jumpers which may be useful for something else.

The last few days I was working on Wayne Warthen's RomWBW for K80W and Eazy80.  In his latest RomWBW Wayne has kindly included RomWBW drivers for K80W and Eazy80 based on my bare minimum descriptions and without having actual hardware!  Not unexpectedly they have a few bugs that I managed to patched up, but I've assembled a K80W and Eazy80-512 and shipped to Wayne this morning to thank him and more importantly, so he doesn't have to work in the dark!

I'll continue to update K80W and Eazy80 homepages with new rev2.1 K80W board, design files, software, and updated RomWBW.  One interesting development is Roger (norwestrzh on vcfed.org) has designed his version of Eazy80-512 and it appears to work fine as described here.  Attached is picture of Roger's Eazy80-512. 
Bill

[Bill Shen]

The simple decoding scheme of Eazy80 can only accommodate a 64K flash, W27C512, which is too small to hold the 128KB RomWBW system code.  Currently to boot RomWBW, the ROM program initializes the SD card, figures out the type of SD card, and loads RomWBW system code from SD card via bit-bang SPI interface.  It is working, but is rather slow.

Eazy80 is a simple SBC, so RomWBW is fairly small such that the actual RomWBW code for Eazy80-512 is 96K interspersed with many strings of 0's and FF's.  It occurs to me that a simple compression scheme may reduce the code to fit 64K flash with an equally simple decompression program to restore it back to 96KB in RAM.

Attached is a 64K flash binary for Eazy80-512 that contains the compressed RomWBW and a small program that decompresses it into RAM then executes RomWBW.  With it, Eazy80-512 will boot directly into RomWBW in about a second.
Bill

[pakt...@gmail.com]

Nice move, Bill!

Paul

[Bill Shen]

I created a page in Eazy80 homepage that describes the compression and decompression of RomWBW.

Beside fast booting, another benefit of booting into RomWBW with program stored in ROM is now I can run p-System SD image without serially loading RomWBW.  Still don't know how to use p-System, but now I have no excuse not to learn.
Bill

[pakt...@gmail.com]

Bill, thanks for the updates on the Eazy80 homepage. Will be interesting to study.

Still don't know how to use p-System, but now I have no excuse not to learn.

That makes two of us  8-)

Paul

[Fernando Carolo]

Bill,

Thanks for all the updates and for such an interesting design. I am thinking about building an Eazy80-512 myself and I have a couple of questions, if you don't mind.

I am having trouble finding a 22MHz oscillator and I wonder if there is any issue if I use a spare 20MHz one while I find the correct one. My understanding is that the serial port clock is based on the 3.6864MHz crystal, so the main clock frequency does not matter, right?

My second question is just to confirm that I should just leave the spaces marked for R11 and R13 unpopulated. 

Best,

Fernando

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[pakt...@gmail.com]

Hi Fernando,

I built Eazy80-512 a while ago and also had to figure out the resistors.

There are actually 3 resistors that shouldn't be populated: R11, R13 and R17. And I should warn you that mounting R5-R9, R12, R18 and R19 on the component side may keep the PLCC socket from sitting flush on the board. On my board, I used 1/4 W resistors and the socket is literally sitting up on them. You can always mount the resistors on the solder side.

As to the oscillator, any frequency up to 33Mhz will work, and not affect the serial baud rate. I did get it to pass ZEXALL at 33MHz, but any port I/O caused a hang.

HTH,

Paul

[pakt...@gmail.com]

I should have added that Bill has actually specified 1/8 W resistors in the BOM, so the resistors *might* just fit under the PLCC socket while leaving the socket flush with the board. I've noticed some differences between brands; some have a more "hollow" bottom. My tip is to try before soldering.

(Sorry if I've stepped on your toes here Bill)

Paul

[Bill Shen]

Paul,

I appreciate you helping out explaining R11, 13, 17 should not be populated for 512K mode, and that many resistors should be on the solder side of the board so socket will fit properly.  Yes, I generally design with 1/8W resistors so 1/4 W resistors will be tight fit.  Because IO clock is independent of Z80 clock, I’ve tested Z80 as low as 1.8432mhz and as high as 31mhz.  I’m pleased to see you even tried 33Mhz which some Z80 is capable of reaching, but RAM, ROM, IO also need to keep up.

I’m spending lots of time outdoor as weather warmed up, so I only have few hours in the evening answering questions.

Bill

[pakt...@gmail.com]

You're doing the right thing, Bill. Enjoy the nice weather when you can ;-)

[Fernando Carolo]

Bill,

I just want to report back that I built my EaZy80-512 and it works fine. I followed the advice from this thread about the resistors and placed the ones that are located under the PLCC socket on the back of the board. I was lucky to grab a 20MHz Z80 before they were gone and it is working fine at 22MHz.

I am using the original ROM monitor that loads RomWBW from the SD card and I noticed that it only works for me if I use an "original" SD card, up to 2GB. If I try to use a 4GB card, which is technically an SDHC card, the loader hangs when I try to (B)oot CP/M from option (4). I guess this is a limitation from the loader?

In any case, thanks for your project. It is really nice to see a CP/M machine running so fast!

Best,

Fernando Carolo

To view this discussion visit https://groups.google.com/d/msgid/retro-comp/c5e418b9-dcd9-4130-b2c0-0046f0724b8dn%40googlegroups.com.

[ladislau szilagyi]

Hi Fernardo,

it's not the fastest one... Z80ALL runs at 25.175MHz :)

regards,

Ladislau

[Fernando Carolo]

Hi Ladislau,

Stop making me want more CP/M computers ;-)

At least I have one of the fastest CP/M machines that can be assembled with through-hole parts only.

Best,

Fernando

To view this discussion visit https://groups.google.com/d/msgid/retro-comp/dcb5797d-15ef-4cf3-bf21-b09607ae3690n%40googlegroups.com.

[Bill Shen]

Fernando,
You are correct that the original Eazy80-512 ROM monitor can only handle the original SD card (up to 2GB); it does not know how to deal with SDHC and SDXC card formats.  However, RomWBW does know how to work with SD/SDHC/SDXC cards, so this was the motivation for a version of boot ROM that contains compressing/decompressing of RomWBW, bypassing the needs to recognize various SD formats at boot time.  Booting RomWBW using compression/decompressing is also much faster than the original ROM monitor which loads from SD using bit-bang interface.

I do need to work on a routine that can work with different SD formats because Eazy80 (128KB) version does not have the help of RomWBW; CP/M on 128K version of Eazy80 needs to work with SD cards on its own.

Bill

PS, because Eazy80-512 only has one simple glue logic, it can actually run 25.175MHz reliably, just replace your 22MHz clock with 25.175MHz.  In fact, I just replace it with 29.5MHz and it is running zexall.com instruction test right now.

[Fernando Carolo]

Hi Bill,

I agree that moving to the compressed RomWBW loader in ROM is a better setup. I intend to get there after I run a couple of tests with the existing expansion cards I have, to try and see which ones can work at 22MHz or more. Then I can build an image with the drivers I want and write it to the ROM. At least until I order a few more oscillators and have to start the tests again.

Thanks,

Fernando

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[pakt...@gmail.com]

Not to forget the "simple" Simple80 ;-) The one in the picture runs at 29.5MHz. 

For RAM, it's using a 15ns IS61C1024-15N 32-pin "skinny-dip" mounted on an adapter board, and a CMOS SIO/2. Only drawback with this setup is that serial needs to be jacked up to 230400!

Paul