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RE: [N8VEM-S100:6025] Dual IDE/CF V2a

Guys, it’s unclear to me why you are having so much trouble with the Dual IDE/CF board.  I never have an issue with it.  Offhand the CPU’s I have use it with are:-

Cromemco CPU-Z, Intersystems Z80-II, all versions of our own Z80, 8088, 8086, 80286 and  80384 CPU boards. There were some low capacity brands of CF cards it did not work with I seem to remember, but all the Kingston’s I’ve ever used work reliably.  In the past when I got involved it turned out the problem was the 74cxx chips, the CPU or the 8255 being defective.  There is nothing particularly novel/special about that boards circuit. It’s just a few I/O ports on the 8255 talking to the CPU.   The only thing that was “touchy” was the length of the CF cards reset signal.   This was mentioned on the web page.





From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com]
Sent: Thursday, January 15, 2015 8:07 PM
To: n8vem...@googlegroups.com
Subject: Re: [N8VEM-S100:6025] Dual IDE/CF V2a


Rich and Gary,


>> Good points - my Z80 CPU is a decades old Compupro CPU-Z with a vintage Z80 running at rated
>> 6 MHz - nothing fancy there.

One of the CPU cards I've tried is the CompuPro CPU-Z, but at 4 MHz.  I even tried turning on I/O wait states, but nothing changed.  I also tried to get the IDE/CF card to work with a Cromemco ZPU.  Same problems.


>> The card manufacturer is worth looking at. I have  been using a 256 MB Sandisk card.

I've tried a number of different CF modules.  In frustration, I bought some of the 4 GB Kingstons pictured on John's build page (the ones with the white flowers on them).  Didn't change anything.


>> What bothers me about this discussion is that other IDE-CF interfaces appear to work
>> without problems - for example John Coffman's ECB SBC Mk IV works with anything I
>> have thrown at it with no issues. Same for my digital cameras that work flawlessly with
>> any CF card I have tried. Something about this S100 board is marginal.

Well .... I've designed and built 2 different Z80 SBC's with CF interfaces, and both work flawlessly.  On both, the CF interface is directly on the Z80 bus signals (no 8255).  Both run at 10 MHz.  I have even designed and built a 68k SBC (again, running at 10 MHz).  On the 68k, I was forced to use an 8255 because I couldn't figure out how to utilize the raw 68k bus signals for the CF.  The biggest problem is that the 68k R/W* signal isn't a pulse as such, it just switches level.  The 68k CF works flawlessly too, but I'm still in the process of trying to figure out how to get CP/M 68k up on it.  Everything I've tried with the 68k CF seems to work well ... so far.

No worries -- my efforts to build a "diskless" S-100 system continues.  I have designed and built an S-100 RAMdrive.  It is 4 MB, and battery backed.  It looks like 4 ports to the S-100 bus.  Without the latency of rotational media, even a 4 MHz Z80 is quite responsive.  I use the second serial port of the N8VEM serial card to access a UDrive, and I can read and write files from/to that.  No floppies or hard drives required.  BTW, that serial card is a real "keeper" -- excellent, once you figure out the serial port headers.  I can run a very nice S-100 system with just a cpu card, 64k memory card, the above mentioned serial card, and my RAMdrive.  I'd love to have an IDE/CF card working, but it appears that won't happen.  Anyone who might be interested in any of this can see the 68k and RAMdrive projects on my Web site:  www.hanscom.us.




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