Dangerous Prototypes Open Source Hardware

Re: XT-IDE adapter with CPLD builds

Reply #75 – August 31, 2011, 03:25:31 pm

[quote author="J1mbo"]Entirely out of interest, could a CPLD be programmed to interface RAM to an XT?  I was just thinking how simple (looking) the old 256KB RAM expansion boards were, and hence whether by 'mearly' adding an SMD RAM chip of some description then the board could provide IDE and RAM to a system.  I'm not particularly suggesting it should, just thinking out-loud.[/quote]

I used to have an 16bit expansion board, up to 3MB, 2 x RS232, and LPT, was huge and heavy. ill donate a hand full of 72pin edo to the developer.

Re: XT-IDE adapter with CPLD builds

Reply #76 – August 31, 2011, 11:14:38 pm

Hi Pietja,

I just wanted to check that the XC9572XL code was definitely updated after the address bit switch problem, as the issue I have does seem to be very much like that you found in testing back on Aug 16, i.e. detects drives and BIOS image is good (checked with DEBUG dump compared to loading image) but I can't read or write to the drive.  Tried a couple of drives and cables (40- and 80-wire).

In the mean time, I've got a compact flash adapter coming soon so maybe that will be more successful!

Many thanks!

Re: XT-IDE adapter with CPLD builds

Reply #77 – August 31, 2011, 11:29:23 pm

I just rebuild the xsvf file again with the correct sources and attached it here.
(remove ".txt" from the file otherwise i couldn't upload it)

If this file works then the ones in the svn are wrong and i will update them asap.

Re: XT-IDE adapter with CPLD builds

Reply #78 – August 31, 2011, 11:31:09 pm

Here's my dodgy soldering!

Re: XT-IDE adapter with CPLD builds

Reply #79 – August 31, 2011, 11:36:43 pm

Many thanks Pietja, there are differences between that and the last version, so I will give it a whirl!

Re: XT-IDE adapter with CPLD builds

Reply #80 – September 01, 2011, 12:11:17 am

Unfortunately there's no change... it's late again so I'll look more tomorrow.  Thanks again.

Re: XT-IDE adapter with CPLD builds

Reply #81 – September 01, 2011, 01:15:59 pm

Just to check, the CPLD code above is for use with the standard (non-Chuck-mod) BIOS, correct?

Re: XT-IDE adapter with CPLD builds

Reply #82 – September 01, 2011, 01:23:31 pm

That's correct, the "Chuck mod" uses a file name to reflect the mod.
XTideCPLD1_XC9572XL_3.3V_v1a_Chuck_mod.xsvf

Re: XT-IDE adapter with CPLD builds

Reply #83 – September 02, 2011, 05:45:27 pm

Some success!  I peeled back the hot-melt glue and reworked the jump leads... ansd the board now works!

So far tested in a P200 OK - will pull out a proper XT later to see what happens there.

Also just to reiterate my thanks for the very patient assistance that you guys have provided :)

Re: XT-IDE adapter with CPLD builds

Reply #84 – September 02, 2011, 06:46:26 pm

Congratulations on finding the error.

I'm curious if the file from the svn also worked ?

Re: XT-IDE adapter with CPLD builds

Reply #85 – September 02, 2011, 09:35:17 pm

I can check certainly.  Quick update - seems to work perfectly in a real IBM XT 5160!

Performance stats with my tester - 90KB/s write, 129KB/s read, 4.8 IOPS (8k), 6.3 IOPS (sector).

Re: XT-IDE adapter with CPLD builds

Reply #86 – September 02, 2011, 10:27:11 pm

OK final update I think - the 9572XL CPLD code in SVN is fine for both standard and chuck-mod versions.  Sorry to have wasted your time on that.

With the chuck-mod applied in CPLD and EEPROM, in the IBM PC-XT 5160 the read performance rises to about 230KB/s.  My utility reports incorrect numbers in this configuration though - which I will debug.

What's next!?

Re: XT-IDE adapter with CPLD builds

Reply #87 – September 02, 2011, 10:40:22 pm

Tanks for confirming the svn builds are ok.
I programmed the CPLD from my local directory not the svn, so its good the have someone test the svn ones.


[quote author="J1mbo"]Entirely out of interest, could a CPLD be programmed to interface RAM to an XT?  I was just thinking how simple (looking) the old 256KB RAM expansion boards were, and hence whether by 'mearly' adding an SMD RAM chip of some description then the board could provide IDE and RAM to a system.  I'm not particularly suggesting it should, just thinking out-loud.[/quote]
I've got an Intel Above Board in my 286 testing pc but it needs drivers to work, so i dont think its easy to get working, but i could be wrong.

Re: XT-IDE adapter with CPLD builds

Reply #88 – September 02, 2011, 10:44:15 pm

I was thinking more of XT class RAM expansion boards, so no drivers needed.  Just provide RAM straight on the ISA bus.

Re: XT-IDE adapter with CPLD builds

Reply #89 – September 05, 2011, 09:24:06 am

Congrats on the successful test! Thanks for posting the benchmark results.

I think a simple RAM expansion card, if it just sits on an address range, probably doesn't need a CPLD at all. It seems like typical SRAM chips could be controlled directly from the bus. If you want DRAM you do need a complicated controller, but the advantages in this situation are minimal compared to the expense of prototyping a working DRAM driver.