wiretap wrote on 2021-08-29, 03:04:

Here's the first rev of the first board soldered up. I'll setup a system to test it on and flash a BASIC ROM for testing. This i […]
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Here's the first rev of the first board soldered up. I'll setup a system to test it on and flash a BASIC ROM for testing. This is really the first day in about a week I've been able to have 20 minutes free.. haha. I've been covering for my manager at work while he's on vacation and it's been some lovely 18hr work days. I hope to have Monday free to get this tested, but no guarantees. My wife starts back to college Monday, so I'll have to keep my 4-year old occupied as well. Busy times 🤣.

Thought I had some 20-pin sockets for the 688 chip, but apparently not. I'll have to order some.

that looks great thank you for sharing 😀

I have to setup a few different test rigs to test the two cards soon. I have one more work trip to go on this coming week, then I should be free for more play time after that.

Have you had a chance to test these? I am planning to order some PCBs and build a few for myself, for use as small cheap XT-IDE boards to use in systems having issues with larger HDDs..

Sadly not yet. Dealing with several health issues in the family and I haven't had time to setup any older systems for testing.

wiretap wrote on 2021-11-02, 10:31:

Sadly not yet. Dealing with several health issues in the family and I haven't had time to setup any older systems for testing.

Sorry to hear that I hope everyone is fine. I will order some PCBs and do some testing myself I think, I'll let you know how that turns out 😀

Thanks. What I had planned on doing was use the EEPROM card in a system to flash XT-IDE, and if that works, dump the pre-configured bin file to be flashed onto an EPROM for testing the other card.

I am planning on building the EEPROM version, and doing the XT-IDE BIOS flashing with a programmer. Should work, right?

You have to run the XT-IDE tool in DOS to configure the custom bin file, then dump it for burning, or just burn it using the EEPROM card itself.

wiretap wrote on 2021-11-02, 11:25:

You have to run the XT-IDE tool in DOS to configure the custom bin file, then dump it for burning, or just burn it using the EEPROM card itself.

Yeah but the configuration can be done in DOSBOX, and then the burning can be done in an EEPROM programmer right? Sorry, I'm an XT-IDE virgin 😁

Yes

One last question: Is the main reason there is an EEPROM board to enable flashing it while in the computer? Considering I can program the EEPROM elsewhere, can the original EPROM board be used with a 28C256/512 EEPROM?

Pinouts are different on the chips. You'd have to mod it to work. ( https://electronics.stackexchange.com/questio … -how-to-wire-we ) But the EEPROM board enables flashing on the computer itself if you put on the enable jumper. But yes, you could flash the chip outside the system beforehand.

Two quick questions for the EEPROM card:

1. Would electrolytic caps work in place of tantalums in this?
2. a) Would the card work without the write enable switch?
2. a) Upon checking the circuit, I think the answer to the above is NO, so I guess we could just bridge 1-2 and 4-5 permanently to make it work in write protected mode?

1Permanent Write Protect
21-2 3
34-5 6

2. b) Can the switch be replaced with a jumper block instead? So that shunting 1-2,4-5 protects the EEPROM, and 2-3, 5-6 write enables it?

Here's a (possibly dumb) question: Could you put DOS on one of these roms, boot off it and (in the case of an EEPROM equipped card) actually mount a partition so you could edit autoexec and config.sys? Sort of like an ancient SSD? That would be kinda cool... At least I think so.

Socket3 ,
put dos on it, yes,
boot off it, yes
mount a partition ... it's an 8 bit card that lives in a 1MB address range in which all your RAM, BIOSs and videoram is located,
which, best case, leaves you with, in ideal circumstances, I think around 368KB, less ideal 256KB, worst... 64K or less.
for which you'll likely need some software to use it.
So, yeah, It's possible...

I have an XT clone with DOS in ROM. It's mapped to the upper memory area with only the bare minimum files (io.sys, msdos.sys, command.com). It's a neat trick but really only useful if you don't have a hard drive.

i can not make it work for some reason. Did it ever worke? I have both cards done. The small one does not want to work. I have not tried the other one as I am waiting for the switch.

wiretap wrote on 2021-07-23, 16:37:

Designed a little boot ROM card this morning for running various ROMs in one of my XT boards that doesn't have additional ROM so […]
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Designed a little boot ROM card this morning for running various ROMs in one of my XT boards that doesn't have additional ROM sockets. It has a jumper block for setting a wide variety of addresses as designated on the silkscreen. Should work on XT-->486 and other systems. I saw some other boards for sale that are similar, but they use more parts and are more expensive -- this should be a pretty cheap option if you want to build just a simple/small boot ROM card. I designed it for a 27C256 EPROM/OTP since those are pretty common and cheap.

KiCAD, gerbers, BOM attached. Not tested yet, but I have some boards on order.

--------------------------------------------------------------------

EEPROM Version that is flashable, supporting 28C64B and 28C256. This one should be better if you need to configure and flash the chip from within the PC itself. (configurable ROMs) - just put the write enable jumper on:

^--the black box (S1) is a little DPDT switch, no 3D model available.

i am sure there is one 10k resistor missing from the circuit. This is the ROM enable.

Yea it is a possibility. I never got to test that board. I'll have to revisit the schematic design when I get back from out of town next month. A bodge could be soldered in place in the meanwhile.

ignore my previous posts.
The small card works like a dream. Obviously I made a mistake when I used the incorrect XTIDE bin. If you look at the picture It only works where the jumper is set to. I tried it in 3 different machines. 2x386 and a 486 machine. The card works with 27c128 and 27c256. Whichever chip you use you will have to make the bin file to fit into the chip.

The bigger card? Hmm. It does not want to work yet. I have the correct chip. I have the correct bin. I just need to find the address where it wants to work.
Follow up.

Both type of cards are working.
Found the address. I use AT28c64. Only the first jumper needed.