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In the case of XT-IDE/XT-CF card, premature failure sounds like a production problem rather than design. 'Mileage will vary', but to date, on my XT-IDE/XT-CF cards, I have seen only experienced failure of the 28C64 EEPROM. Sometimes corrupt contents, fixed by rewriting the 28C64. In those...

Some possibilities that I can think of: 1. Bad/corrupted Supersoft/Landmark ROM's. 2. Odd ROM went into even socket, even ROM went into odd socket. 3. The motherboard is advanced enough that its chipset requires some chipset-unique configuration, something that the Supersoft/Landmark diagnostic...

There should not be a problem using that chip. In my opinion, use of an IC socket is prudent. The "10" is pointing to the 4K block at address 64K, RAM that does not exist in your test configuration. Yes, this is sure to be due to the combination of: - The nature of the failure of your 8255...

Confirmed. Supporting diagram at [here]. IBM changed things in the move to the IBM 5160 (IBM XT). In the IBM 5160, the two RAM related motherboard switches in SW1 now enable/disable motherboard RAM banks. The 5150's populate-motherboard-RAM-banks-first rule can be found in some...

I now see that RTCDRV.EXE displays them.

That is up to you. For now, I will just create an entry along the lines of, "As reported at xxxxx, it appears that in certain circumstances, MacOS 14 overwrites part of the MBR, necessitating the use of FDISK /MBR (from DOS 5 or later) to restore booting from the IDE device ..."

The 1701 error message, has many possible causes. You could try the RAYXTMFM tool at [here] and from that, see if the hard drive subsystem is at least seeing the drive reporting as 'ready'.

I have added the software to the collection at [here]. What I/O ports is the BC88's MC146818 accessed via ?

The RTCDRV.7z password is: trigem

I do not own a Gotek, but I have recorded earlier threads that concern a Gotek in an IBM PC (IBM 5150). • https://forum.vcfed.org/index.php?threads/gotek-emulator-as-primary-floppy-drive-for-ibm-5150.69619/ • an earlier thread is...

No. Others here might. Those are expected to work. FYI: On a second IBM MDA that I have, the RAM chips are AM9114EPC. Very suspicious. If you have not already, you should be investigating the possibility that your tantalum-above-U13 replacement activity did damage to the PCB, e.g. severed a...

I looked more at the circuit diagram. U12 and U13: Character - bits 7 to 4 U14 and U15: Character - bits 3 to 0 U8 and U9: Attribute - bits 7 to 4 (attribute is blinking, etc.) U10 and U11: Attribute - bits 3 to 0 Each chip covers about half of the screen. The first 'half', the top, is 1024...

I did that. I am very confident, based on the circuit, and an experiment that I did, that U13 and U15 are for the top 'half' of the screen, and U12 and U14 are for the bottom 'half'. ( And I confirmed John Elliott's information. The card decodes more than 4 KB of motherboard address space: 32...

I suggest that you be careful there. 'Arcade' CGA is not the same as IBM CGA. Discussed by tomxp411 at [here]. Maybe you have a TV that can accept the composite video from the CGA card's RCA jack. An example screenshot of the AT version of the diagnostic is at [here]. If I put a faulty 8259...

Behaviour that I observed today on my Windows 10 computer: I have recently moved from a Windows 10 desktop computer to a Windows 10 notebook. (Draws less power.) I connected up the Toshiba diskette drive that is shown at [here]. I.e. Actually an FD-05PUB. I brought up a 'normal' command prompt...

I did observe that the IBM CGA card was unaffected. I see in the Supersoft/Landmark Diagnostic ROM (SLDR) code, that the '1 to CRT control port before population of 6845 controller chips data registers' is done for both MDA and CGA. For CGA, is that the SLDR author 'playing safe'? Perhaps I...

After more analysis, it could be U14 or U15. On my to-do list is to work out which.

Further regarding the unexpected characters on the IBM MDA. Looking at the circuit diagram more: U12 and U13: Character - bits 7 to 4 U14 and U15: Character - bits 3 to 0 U8 and U9: Attribute - bits 7 to 4 U10 and U11: Attribute - bits 3 to 0 Each chip does almost half of the screen. So, if we...

I get the impression that you did not read the link that I pointed to in the 'Background' section of post #1. What I believe that I have done is proven the hypothesis in that link. Looking at the video, some readers may believe that my 8253 timer chip is faulty in a way. But my 8253 is still...

Related are posts #7 and #8 in the thread at [here]. There, the change of a space (20h) to an exclamation mark (21h) is a change of bit 0. When I simulated RAM bit 0 on my IBM MDA being stuck high, basically, the whole screen (where spaces) changed to exclamation marks. Only some of the OP's...