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Topic: XT-IDE adapter with CPLD builds (Read 201439 times) previous topic - next topic

Re: XT-IDE adapter with CPLD builds

Reply #90 –
Here's an update on v1b, also in SVN:

Quote
on 3.3V v1b
-put a solder jumper for the CPLD voltage select, default is with 3.3V VREG and the jumper is open, there should be no VREG when in 5V and the jumper should be shorted out.
-HDD activity LEDs have their individual limiting resistors
-moved HDD led external connector, R5, R4 and R6 to make way for the shrouded 40-pin connector
-connect pin 20 of the IDE connector which is the index pin mostly on IDEs to +5V (Is this correct?) connected through optional jumper
-The 3.3V v1b can now be used with 5V with only the CPLD voltage selection properly configured.
-updated CPLD CX9572 package, has now pin 1 marker :)

I need to double-check the change list, but I think this is probably the next revision for now. More major updates can be made to the 100% CPLD-based device.
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Re: XT-IDE adapter with CPLD builds

Reply #91 –
Great stuff, can I just ask for a little more spacing between the 40-pin header and JP2, as a straight box-type header fouls that.

Would still be nice to have a CF socket on board, but I understand that we could go on for ever with feature requests!

Re: XT-IDE adapter with CPLD builds

Reply #92 –
Thanks for the feedback. My goal for v2 is to be a big CPLD, EEPROM, and an on-board CF card (only, no big IDE maybe...).

I don't see a lot of room to move the jumper much more. Using a bigger CPLD on v2 will open up a ton of board space and simplify routing. Then it should be super easy to keep headers clear and accessible.
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Re: XT-IDE adapter with CPLD builds

Reply #93 –
OK great, sorry I'd mis-read the comment above about the 100% CPLD version.  All sounds good to me then, looks that pin-20 supply can be 3.3 or 5v (for example here) (jumper for either, but would there be enough mA available from the 3.3v regulator?).

Re: XT-IDE adapter with CPLD builds

Reply #94 –
There's 150mA from the vreg, but it probably gets pretty hot at more than 100mA in that tiny package.
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Re: XT-IDE adapter with CPLD builds

Reply #95 –
It looks to me that power consumption for DoM could be anything from 20mA to about 100mA, but it also looks that all of them I can find will take a 5V input too.  Perhaps it could be jumperable between non/3.3/5v, with another VRM for its supply.  But is this over complicating the issue?

BTW, just to add.  I notice that all my old 'commercial' ISA cards have gold plated slot contacts - why is that, and would a 'production' xt/ide need similar?

Re: XT-IDE adapter with CPLD builds

Reply #96 –
I assume the contacts are plated to prevent tarnishing and give the best possible connection over long-term use. I don't actually know how to make PCBs with gold plated contacts or if our fab house can do it :)
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Re: XT-IDE adapter with CPLD builds

Reply #97 –
A modest contribution to the project ... a hardcard like in the old times, using a 2"5 HDD. the connection to the disk is made with a small piece of cable. Moving the IDE-44 connector to the left could be possible also. I will be glad to make the modification for V2. The HDD is light enough to be screwed to the pcb without bending over time.

Re: XT-IDE adapter with CPLD builds

Reply #98 –
By the way, I was a bit surprised to see all the VCC lines tied together. This theorically induces problems if the voltage level is not quite the same on the extremities of the connections due to power consumption on the board. But I checked the original IBM PC 5160 schematics and they did it as well, so ... I guess it's OK :-)

Re: XT-IDE adapter with CPLD builds

Reply #99 –
Nice idea attaching a board to the end. We're lucky that Eagle free version lets you extend the board outside allowable dimensions :)
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Re: XT-IDE adapter with CPLD builds

Reply #100 –
Actually, I had to use a non-free version of Eagle. You are right, the board and traces are limitless in the free version. However, I wanted to have grounded holes for the screws of the hard disk. These holes are considered by Eagle as components and therefore cannot be placed where I placed them, in the free version. There's a workaround if you want to stick to the free version : standard holes and vias are not limited either, so you may replace grounded holes with standard holes with a via over them with the same diameter. Only con, they will not appear in the schematic.

Re: XT-IDE adapter with CPLD builds

Reply #101 –
The hard card is a very neat idea certainly, and is the approach that's been taken by the PCjr port, JR-IDE.

Because of the different ideas and options being floated, I've taken a little liberty in putting up a poll on vintage-computer.com, to get some idea of what the most popular options are presently.  Currently the poll is showing some support for a hard card, but the most popular option by some margin is to have a compact flash socket and the 40-pin header.  See the poll and ensuing discussion here.

Then there's the question of the likely life of compact flash and indeed compatibility.  CF has seen something of an upsurge recently in the pro camera space, so I'm going to test all the CF's I can get my hands on to try and assess any compatibility issues.

Anyway, hope this is all of some use!

Re: XT-IDE adapter with CPLD builds

Reply #102 –
This poll is a nice idea. While I like the idea of mimicking a hard disk with the network, I think it is out of scope of the project. USB on a PC-XT for mass storage is utopic : I am presently working on a USB interface for a french 8 bit computer similar to the C64 and while low speed is very easy to achieve (keyboards, mice), full speed is a nightmare due to extremely short timings (the devices simply time out and often reject the enumeration).

I have also developed a CF interface for my french 8 bit computer and I have quite some knowledge about CFs. The issues with modern CFs are related to the metaconfiguration of the card, which is not quite achievable through the ATA interface itself. But I managed to make 4 and 8 GB CFs work on my machine (my interface does not use ATA but direct memory mapping). Using all kinds of CFs on the XT-IDE would mean adding an extra software configuration step at boot time and a bit of electronics, not much, to access the extra registers of the CF and configure an ATA mode compatible with the XT-IDE. Which is certainly achievable with a bigger CPLD.

My original goal, before discovering the XT-IDE project was to design a hardcard to replace the one I have (A WD Filecard with 20MB) which has been running fine for 25 years now (not a single bad sector). It's just perfect, except for its capacity.  A 2 GB 2"5 hard disk is a few bucks on ebay, so with the XT-IDE, this will perfectly fit my needs.

nb. I am pretty confident that when the 2 GB hard disk will have worn off, the WD Filecard will still be operational ;-)

Re: XT-IDE adapter with CPLD builds

Reply #103 –
Thanks for sharing the poll in the vintage computer forum.

Thanks for the info on the CF cards, that addresses some of the concerns about modern CF cards discussed in the forum.
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Re: XT-IDE adapter with CPLD builds

Reply #104 –
Quick update - I imaged three CF cards with 10MB FAT-12 partition containing DOS 2.1.  Results, with 3.3v CPLD card with Chuck Mod CPLD code & BIOS, are thus with CF supply at 5V:

1. Kingston Elite Pro 50x 2GB (made by Samsung).  Detected and booted fine.  Chkdsk found numerous errors.
2. SanDisk Ultra 30MB/s 4GB.  Detected and booted fine, chkdsk no errors, ran Word 4 no problems.
3. Industrial Compact Flash 1GB.  Detected OK, reported slave "too old".  Booted fine, chkdsk no errors, ran Word 4 no problems.

Changing the CF supply to 3.3V, all three cards worked properly (booted, chkdsk no errors, Word 4 started fine).