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Forthcoming XT-IDE Board - Cast Your Vote

Forthcoming XT-IDE Board - Cast Your Vote

  • As original XT-IDE, with a 40-pin header only

    Votes: 4 10.5%
  • With a 44-pin header and board space to mount a 2.5" IDE HDD (i.e. a hard-card)

    Votes: 7 18.4%
  • With an optional Compact Flash socket (as master or slave) and a 40-pin header

    Votes: 26 68.4%
  • With a Compact Flash socket only

    Votes: 1 2.6%

  • Total voters
    38
  • Poll closed .
Thanks, but that is a PCI bracket (card mount tabs are on the wrong side). If you can find an ISA bracket that would be great though!
 
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Not only that but the part Shadow Lord linked is basically a custom part. All the prices for quantities up to 25+ are essentially the same and very pricey. You would have to buy 50 to 100 or more to get the unit costs reasonable.
 
A possible solution for ISA vs PCI mounting would be to just use 1" hollow plastic standoffs and longer screws, so that you can still mount the PCB on the ISA side but use the mounting tabs on the PCI side.
 
Thanks, but that is a PCI bracket (card mount tabs are on the wrong side). If you can find an ISA bracket that would be great though!

I realize that but finding an ISA one is going to be impossible in prefab and a custom one would be expensive for a small run. The mounting holes are easily fixed w/ spacers and longer screws.

Not only that but the part Shadow Lord linked is basically a custom part. All the prices for quantities up to 25+ are essentially the same and very pricey. You would have to buy 50 to 100 or more to get the unit costs reasonable.

I think I already alluded to this in my post (the cost drops off significantly at quantities of 50 or more). I assumed that there would at least be a 50 run and maybe even a 100 run. At those numbers trying to mill blank brackets w/ any precision by hand is going to be expensive. Of course if you plan only on a run of 10 then yes by all means do it by hand.

BTW: this was just an example. They are hardly the only game in town and better deals maybe found. This was just one I found w/ quick googling at 2 am ;).
 
A possible solution for ISA vs PCI mounting would be to just use 1" hollow plastic standoffs and longer screws, so that you can still mount the PCB on the ISA side but use the mounting tabs on the PCI side.

My thought exactly. Its just a question of the production run (i.e. how many do we think are needed?)
 
The poll at the top suggests total immediate demand is probably only in the 20s, and some of those may well have purchased one of Andrew's XT/IDE v2 boards. DP also have (I assume) 10 boards on-order, so the market for the compact flash board, also bearing in mind assemblers will need to be willing to have a stab at SMT - probably 10 boards, tops.

Using spacers is a fair enough idea. But, that could then limit board placement to the right-most slot, or necessitate an empty slot next to it (to avoid potentially shorting the adjacent board). Wouldn't have that problem in a 5150 of course.
 
Yeah, I am not sure how much stock I would put in that voting. Heck, I haven't even voted (I think) and I would buy one. The reality is if it works as planned (8 bit ISA CF adapter w/ easy access from the back of the case) it will be an almost indispensable tool in the kits of anyone who uses old computers (hobbyist, collectors, support departments). I am a guy, like most of us here I would assume, who has computers w/ all sorts of floppy drives and sizes. Even then though I don't always have a certain program in a certain disk format (e.g. files are on 1.2mb disks but the computer I need them on only has 360KB drives). My biggest issue right now is getting my computers up and running enough to get them on the LAN where I can install software from. I think once there is a working prototype and prices are determined the orders will go up. But as has been pointed out you will need 50 orders or so for prices to drop

As a curiosity how much will it cost you to mill one bracket (taking into account time, equipment, supplies, etc.)? You might find that 30 of milled brackets will cost the same as 50 of the pro ones. In which case you'll get an extra 20 for free...
 
The poll at the top suggests total immediate demand is probably only in the 20s, and some of those may well have purchased one of Andrew's XT/IDE v2 boards. DP also have (I assume) 10 boards on-order, so the market for the compact flash board, also bearing in mind assemblers will need to be willing to have a stab at SMT - probably 10 boards, tops.

Using spacers is a fair enough idea. But, that could then limit board placement to the right-most slot, or necessitate an empty slot next to it (to avoid potentially shorting the adjacent board). Wouldn't have that problem in a 5150 of course.

Would there be a version of the board that does not require the buyer to solder surface mounted components?

While it is not an issue in a IBM PC, the right mounted slot in an IBM XT and many compatibles is the dreaded slot 8. Can or does the design work in slot 8?
 
What about ordering the PCI brackets stamped but unbent and letting the ones who will order the boards/kits bend them the opposite way from PCI to make it fit the ISA board and slot?

Or just bending the prebent PCI ones , a risk cracking the metal but it could work.
 
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I've revisited the idea of having 40-pin and CF on the same card - here's the result. The board has master/slave CF config, switchable pin-20 VCC (for DoM power), won't support IRQ or DMA based operation, but the CPLD has the necessary connections to support code providing functionality of the original XT/IDE, 'Chuck-mod' (enhanced read) and also any future memory-mapped IO.

With this size board it's pretty tricky; there just isn't enough room to make it work without some highly dubious routing. Attached a design - any comments on these would be very gratefully received. Main problem is that traces run very close together, and to e.g. CF mounting holes, and right to the top edge of the board. Someone with more experience could do a better job with it I'm sure.

In particular, a second pair of eyes on the schematic would be great (edit - I've picked up missing ground connection on CF-CSEL DIP switch already, just not updated the ZIP file). CF slot is first-in-line, then routed on to the 40-pin header. PDIAG and IOCS16 are linked between CF slot and 40-pin header, 40-pin header also has DMARQ with 5.6k PD. None of those go back to the CPLD.

Do we need B8 (/nows) hooked up? According to the PC/XT technical reference it's not defined on the XT anyway (listed as reserved).

Design pack here.

xt-cf-ide.jpg

Re PC/XT slot 8, I can't answer that. The technical reference describes the signals on JP8 preceded with an X, i.e. XD0 as opposed to D0 (page 1-45). Re SMT, minimum run for professionally assembled boards is qty 100 I think, but I just don't have the capital available to fund that.
 
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Hi, in case anyone is interested in this, I've been chipping away at my compact flash version of the XT/IDE adapter, and am currently awaiting delivery of the first prototype PCBs. For the custom made ISA slot bracket there are a couple of options, laser cutting and CNC stamping; laser isn't too bad with a qty.50. Bracket/board/parts, on qty.50, looking at ~$30.

More info on my wiki page: http://vintage-blog.peacon.co.uk/wiki/Peacon_XT-CF_Board

I'd note that the board may not even work and the CPLD code isn't done yet - so just an update really.
 
It would be interesting to see an XTIDE that was port- and interface-compatible with a standard XT controller. I'm not expecting it, just speculating.
 
Yes, the early XTA drives had port organization essentially identical to the MFM controllers. I've always used either the WD 8-bit or IBM (Xebec) port descriptions. BIOS ROMs seem to be swappable between them.

It would certainly be more "authentic" than the current XTIDE, which is compatible at a BIOS level only, but juggling the differences between ATA and XTA would be a subject more for MCU or FPGA implementation.

It might be fun to program an FPGA with a simple processor to handle this and have it interface to a couple of SDHC memories. Of course, one gotcha is that the XTA interface is limited as to the amount of storage it can address:

Command "packet" structure:

Code:
struct XTCommandBlock {
  unsigned char CommandClass:3;
  unsigned char Opcode:5;
  unsigned char Reserved:2;
  unsigned char Drive:1;
  unsigned char Head:5;
  unsigned char CylinderHigh:3;
  unsigned char Sector:5;
  unsigned char CylinderLow;
  unsigned char BlockLow;
  unsigned char RetryCount:2;
  unsigned char Unused:3;
  unsigned char StepRate:3;
}

So, as-is, you've got an 11-bit cylinder, 5-bit head, and 5 bit sector field. However, since the XTA/ST412 interface only provides for 8 or 16 heads, you have 1 or 2 bits left over in the "head" field, so you could go to 4K or 8K cylinders, as some manufacturers did.
 
Hmm so a drop-in card that would work with the on-board MFM/RLL BIOS? It's an interesting idea certainly, but isn't the controller BIOS usually on the card itself?
 
Not too sure how to put this.... so I put up this survey, and then built the card with the least responses - one with a compact-flash header only!

http://vintage-blog.peacon.co.uk/xtide-the-future/

It's awkward to have 40-pin on it too, and personally I'm not convinced there is any point since CF cards are so cheap and have more capacity that could ever be used in an XT. But that's just my opinion of course! Enjoy...
 
If I had any clue how to surface mount components I would get one of these in a heartbeat, but as it stands I am not all that confident in my soldering skills of standard through PCB components...
 
If I had any clue how to surface mount components I would get one of these in a heartbeat, but as it stands I am not all that confident in my soldering skills of standard through PCB components...

Same here, I am comfortable with through the hole, or even surface mount provided its got large pads, but I do not have the dexterity or steady hand to pull off soldering those tiny pins on a CPLD or other SMT parts.

EDIT: I have seen some CPLDs and what that come mounted on a ZIF or DIP package that you can buy, would there be any way to do something like that for this project, I think that would be something most people here could handle soldering.
 
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Thanks, I kind of feared as much. SMT does take some practice - but the trick is to blob it on with some flux, then suck up the excess with more flux and solder wick, leaving the solder just around each foot.
 
EDIT: I have seen some CPLDs and what that come mounted on a ZIF or DIP package that you can buy, would there be any way to do something like that for this project, I think that would be something most people here could handle soldering.

Take a look at "Schmart Boards", little boards with a raised mask so that device mounting is very easy. Here's an example that mounts a QFN-48 to a DIP configuration They're not exactly cheap, but they're an option.
 
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