H8 Memory Test Procedure...

[Joseph Travis]

I've been asked several times in the past, how to troubleshoot H8 memory boards.  As luck would have it, I'm currently troubleshooting 5 SRAM boards and decided I would document my procedure in hopes that others may find it beneficial.

H8 Memory Test Procedure

If your H8 has an H17 Floppy Disk Controller or the HA8-6 Z80 CPU Board, there is a built-in RAM test that you can use to help debug your memory board(s).  Use the following steps to execute the RAM test.

1. Perform a reset by pressing and releasing the '0' and '/' keys simultaneously.
2. Enter the following sequence: REG, PC, ALTER, 030 003, ALTER, REG, BC, GO, GO

The 3 left digits on the front panel will display the value being written to all RAM addresses starting from 040 000 and increment the value in each pass.  If an error occurs, the H8 will beep and stop the test.

3. Write down the value displayed on the 3 leftmost digits.
4. Enter: REG, HL to display the 6 digit address of the failure and write it down.
5. Enter: MEM followed by the address, the 3 rightmost digits will display the value read from that location.  Write it down.
6. Using the value written vs. the value read, you should be able to determine the faulty bit location (0-7).  Use a programmer's calculator to convert from octal to binary if the mental gymnastics necessary are too difficult to perform.
7. Convert the memory address location from split octal to your preferred number base, divide that number by the memory size of the RAM used on your memory board(s) which should be 4096 if using any of the SRAM boards or 16384 if using a 64K DRAM board.  That value will identify which bank the faulty RAM is located in.
8. Use the memory board documentation / schematics to identify the proper IC.

Good luck!

Joe

[Geo Monroe]

Keep in mind if you are configured for org 0 operation your rom contents maybe copied into ram and your ram on the controller card my not be accessible.

George

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[Joseph Travis]

Just to clarify, the built-in RAM test starts at 8K (040 000) and tests up to the top of memory. The easiest way to test the bank of RAM below 8K is to use the switches / jumpers on the memory board(s) to reconfigure their starting addresses.  Yah, it's a bit slow and tedious but this is the way we did it "back in the day".

BTW - If you have multiple memory boards, you'll find the memory test runs faster with lesser amounts of memory.  I find it much easier to test just one or two boards at a time.

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[glenn.f...@gmail.com]

So thanks for posting this discussion, Joe. it’s been a little quiet here lately. My two cents on top (hopefully I won’t go overboard on information dump!):

 

• (nitpick) from: https://sebhc.github.io/sebhc/software/Roms/SYDD/HOS1SL_2_07_SYDD.PDF

 

Technically the ROM-based RAM test goes from 40.100 to the top of RAM minus 64.  The 100 (octal) bytes of RAM at the bottom are used by the panel monitor and the 64 (decimal) bytes at the top are the stack area. As Joe says, in an ORG0 configuration you can’t test the bottom 8K in place as relocated ROM code resides there. Best bet is to move (preferably via reconfiguration of boards) that portion of RAM to an upper address space for testing as Joe suggests.

 

 

• Note the HLT instruction above. It’s there to pause to allow you to change the range under test. After you hit the first “GO” in Joe’s instructions the system will halt. You can then change HL (starting address) or DE (last address to test) before hitting the second “GO” to start the test.

 

• If you have an H17 board it has 1K of RAM chips on the board. These reside in low RAM from 024.000 to 027.377. The H17 operation manual describes how to use the above test routine to test this segment of memory. If you are using a Z80 or 8080 with the XCON-8 ROM and ORG0 your H17 board should have been modified so that these chips are not used (instead system RAM occupies the entire lower 8K space).

 

• On power-up the panel monitor does a quick scan to find the top of RAM. It will stop when it encounters either bad RAM or a gap in memory boards. It then subtracts 1 from the first non-RAM location and sets that to be the Stack Pointer (SP). I recommend configuring the RAM boards so that there is a gap between the top of the “known good” RAM boards and the “board(s) under test”.  For example, if you have a known good 8K board installed at 040.000 then set the board under test to start at, say, 200.000. The “known good” RAM will range from 040.000 to 077.377. The board under test will start at 200.000 and go to:
• 217.377 (if test board is 4K)
• 237.277 (if test board is 8K)
• 277.377 (if test board is 16K)

You can then set HL and DE accordingly to test the range you need. The attached Excel spreadsheet may be useful for this.

 

• If you don’t have an H17, Z80 or XCON8 ROM you can manually enter the memory test program from the H8 Operation manual (attached PDF). See instructions on P. 9 for entering the program. Note the start and end addresses must be specified in RAM (040.101 and 040.104 respectively).

 

• For intermittent RAM failures you may want to execute a more in-depth test. HUG Utilities disk VIII (885-1062 disk A) contains a more thorough testing program. The disk image is available on the SEB Hug Archive (volume 3) sebhc.github.io/sebhc/software/Applications/H8DCATALOG_VOL3.HTML
  You can use Darrell Pelan’s very useful H8D Utility to extract these files and copy to your system:
  https://github.com/sebhc/sebhc/wiki#h8dutility

 

• A very useful board to have for testing RAM is Norberto’s “H8-8080A-64KB-RAM-ORG0” board
  https://koyado.com/heathkit/New-H8-Website/h8-8080a-64kb-board.html
  This board lets you enable or disable any of the 8 8K memory banks. It also has a battery backup for the on-board RAM so that, for example, if you load a memory test program in RAM it will stay there until overwritten. It also has the “ORG 0” logic, effectively replacing the HA-8-8 Extended Configuration board. Blank PCBs for the 64K RAM board are available from Todd Goodman.

 

• If you have an H89 with the MTR-90 monitor there is a “T” command in the monitor for testing RAM. If you have an older monitor (MTR-89 or 88) there is a test routine at 007.375 so just do G 7375 to initiate the test. You can have the RAM test run automatically on power on by setting SW501 (on the CPU board) switch 5 to “0” (you must reset it to “1” to resume normal operation).

 

Happy to try and answer any questions this discussion may generate…

 

• Glenn

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[Joseph Travis]

Thank you Glenn!  You can say I'm a practitioner of the KISS principle and tend to leave out details which some might have difficulty understanding or not necessarily care about.  I do appreciate all of the additional info you provided and wish it was composed as an article and published in REMarks.

For anyone following along, the method I described is what "I use" to bring up an unknown system.  I minimize the hardware down to the essentials, CPU and RAM then go from there.  Some memory failures won't allow you to boot let alone run a better memory test.  It seems to me that using a different CPU board such as the H8-808A-64KB-RAM-ORG0 only complicates / confuses the matter and isn't really necessary.  Please don't get me wrong, I'm not poo-pooing the idea - go with what you know.  I will deviate from my basic procedure if / when necessary.

I didn't mention the H89 memory test because I was talking about the H8.  Testing the H89 uses a different procedure.

Best Regards (and I mean it),

Joe

To view this discussion visit https://groups.google.com/d/msgid/sebhc/1e1201dc7cbd%241bfbc420%2453f34c60%24%40gmail.com.

[Glenn Roberts]

It is always good to hear about what everyone’s doing. Anyone have any interesting updates? Or questions? Tales of woe? 😀

Sent from my iPad

On Jan 3, 2026, at 12:20 PM, Joseph Travis <jtravi...@gmail.com> wrote:



Thank you Glenn!  You can say I'm a practitioner of the KISS principle and tend to leave out details which some might have difficulty understanding or not necessarily care about.  I do appreciate all of the additional info you provided and wish it was composed as an article and published in REMarks.

For anyone following along, the method I described is what "I use" to bring up an unknown system.  I minimize the hardware down to the essentials, CPU and RAM then go from there.  Some memory failures won't allow you to boot let alone run a better memory test.  It seems to me that using a different CPU board such as the H8-808A-64KB-RAM-ORG0 only complicates / confuses the matter and isn't really necessary.  Please don't get me wrong, I'm not poo-pooing the idea - go with what you know.  I will deviate from my basic procedure if / when necessary.

I didn't mention the H89 memory test because I was talking about the H8.  Testing the H89 uses a different procedure.

Best Regards (and I mean it),

Joe

On Sat, Jan 3, 2026 at 9:27 AM <glenn.f...@gmail.com> wrote:

So thanks for posting this discussion, Joe. it’s been a little quiet here lately. My two cents on top (hopefully I won’t go overboard on information dump!):

 

• (nitpick) from: https://sebhc.github.io/sebhc/software/Roms/SYDD/HOS1SL_2_07_SYDD.PDF

 

Technically the ROM-based RAM test goes from 40.100 to the top of RAM minus 64.  The 100 (octal) bytes of RAM at the bottom are used by the panel monitor and the 64 (decimal) bytes at the top are the stack area. As Joe says, in an ORG0 configuration you can’t test the bottom 8K in place as relocated ROM code resides there. Best bet is to move (preferably via reconfiguration of boards) that portion of RAM to an upper address space for testing as Joe suggests.

 

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[B9]

Not an interesting update, yet, but I got distracted from fixing my floppy drive with learning 8080 assembly. Wrote a shim which works with Travis's BOOTSTRP to load .abs files directly over the serial port. Oh, and I learned a little Forth so I could make a version of H89TRANS that is platform independent (or at least tries to be).

[Thom Cherryhomes]

Mine is on the bench. Slowly working through bring-up issues with the H89 FujiNet.

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[glenn.f...@gmail.com]

So maybe I'll answer my own question with not just activities but "resolutions" (goals?) for 2026 and my Heathkit hobby:
- develop and demonstrate some fun new Heathkit capabilities at VCF East
- get to one or more of the east coast vintage museums (e.g LSSM, System Source, etc.)
- finalize testing, documenting of the NC Super89 and Sigmasoft & Systems capabilities for the H89
- get back into writing for the group - more REMarks! Etc...
- improve the organization of our web spaces and repositories
- continue to write useful software and update, document tools I support (VDIP, jukebox, etc.)
- downsize my collection (share the wealth)
- complete my H11 setup (currently boots RT11 via SCSI)
- Build a color Z120 (LED screen in case).
- Get the UCSD P system working on a hard drive system (Z67-IDE+, dual CF, etc.)
- archive the disks that I have and share them
- do something fun and interesting with the ET-3400
- help save systems and software whenever I can
- build cool new stuff, especially mixing old and new tech.
- help other SEBHCers wherever I can to achieve their own goals

Hey if I get half that done it'll be a good year! 😊

- glenn

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Sent: Saturday, January 3, 2026 6:54 PM
To: se...@googlegroups.com

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[Mike Cassidy]

Great list of goals Glenn. As is said - under promise but over deliver.    I'd like to second an earlier recommendation from Joe that you publish a next edition of your REMarks newsletters.  Your writeup on H8 Memory Test Procedures is fascinating and a great example of the knowledge base that exists in the heads of guys like you, Joe, Norberto and many others that have been at this for awhile.  One idea for your next REMarks could be a collection of "Tips and Techniques." Those of us newer to the Society would certainly benefit from a handy reference guide of interesting tips - things that are likely buried in hundreds of pages of reference guides that one might only ever stumble onto but find incredibly useful.  Case in point - in your memory test write up I learned that there is a nice memory test routine baked into the H89 monitor - MTR89.  A simple G 7375 initiates that test.  I hope to never have to use it but it would beat keying in the code.  I pulled out my MTR-89 Op Manual and I see that this test is referenced there.  But admittedly I have not studied the text. Nor the hundreds of pages in the HDOS3 manual.  If I read these and others cover-to-cover I'm betting there are dozens of nifty tricks worth knowing.  I've been through many of the REM magazines you gave me and dog-eared many a page with good-to-know pointers.  But those tips are still spread out across lots of paper.  I have a folder on my computer where I often save discussions posted by you and other Society experts so they don't get lost.  But it is just a collection of emails.  Anyway - regardless of the content - it is time for REMarks Issue 7.

As far as updates - or my list of goals - back to the MTR89.  I now have what I need to upgrade my H89 to MTR90 (thanks to Joe for help in programming a few chips).  I know that's a pre-req for installing the H89-Z37 Norberto designed Double-Density Floppy Controller.  I'm not in a big rush to build that board, though all parts are in hand.  But I would like to put MTR90 in motion and it will give me a reason to get inside my H89 and poke around. 

 

I think my next project is to build the Standalone USB Controller for my H8.  Terry Smedley kindly hooked me up with his original design and all that is needed for that build. Norberto designed a good looking standalone USB board but the stock is depleted.  Wonder if there is interest in a re-order?  I'm eager to try out Glenn's Vinculum. There are a few other items on my bench that have been looking at me.  And there is my own resolution to learn some Assembly Language.  I bought the Heathlit Individual Learning Program last year.  

Given the relatively mild late-fall/early-winter temperatures here in the South, I've been working down a long list of outdoor projects.  But we'll get our taste of winter before long and I'll get to the bench.  And looking forward to VCF-East in April.  Will be my first time. So much to learn.

Happy New Year to the Society.  Such a great resource. 

Mike   

        

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Regards,

Mike Cassidy

[glenn.f...@gmail.com]

Good ideas Mike, thanks.  One thing we could use is a “FAQ” (maybe essentially your “tips” idea).  We do get the same questions asked many times. Not sure I’m ready to take that one on but it would be useful…

 

To add USB (VDIP) to an H8 you can either use one of the CPU/Daughterboard combinations (e.g. Z80 Rev4) or, to keep your current CPU use the H17/VDIP1 floppy controller board H8 H17 VDIP1 FSB.  I’m not sure if the instructions indicate how to build out just the VDIP portion but that’s not a bad idea. The board should be available from Todd Goodman (I can’t check at the moment – the server for his site seems to be overloaded?).  Not sure I’d recommend building out Norberto’s old stand-alone H8 USB board but the gerber files are there if someone wanted to. Terry’s design has some nice improvements. I’ll see if I can work with him to get this posted more visibly (see my goals list ☹  )

 

The VDIP1 boards can be hard to find.  Currently Mouser is out of stock but has them on order. You can substitute the V2DIP1-48 as it is functionally equivalent and physically compatible (24 pins, though the jumper settings are configured differently). The V2DIP1-48 uses square pin headers so it won’t work with a machined socket (use dual leaf style instead).

 

Mouser: https://mou.sr/4nDaO55   (389 in stock @$21.56)

Digikey: https://www.digikey.com/short/f71tqwp1  (21 in stock @$24.20)

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[norberto.collado koyado.com]

My list is as follows:

1. H8-UPI interface board
2. S89-UPI interface board
3. H19 - New IGC V2 with 512KB of RAM
4. H89-H17 (new board)
5. H89-H47 (new board)
6. Release S89 V2.0 baseboard
7. Debug/program Z67-SDC-SCSI to replace Z67-IDE+
8. Debug/program H8-Z67-DUAl-IDE board
9. Debug/program Z47-SDC to support H8/H89 H47 interface board.
10. Release S89-SD interface board
11. Release S89-CF interface board
12. Add Terry S. Standalone USB board to the website.
13. Torture Thom to enable the FujiNet network on the H89 system. Debug latest issue reported by Thom with logic analyzer.

My systems:

1. Update H19/green screen with H19-IGC board.

2. Update H8 with UPI controller

That will keep me busy for a while. 

Norberto

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[thego...@gmail.com]

My list is as follows:

 

Build the H88 I picked up from eBay and have a working H89

Build the H89-Z37 board

Attend VFC Midwest

 

A small list but I’ll be happy if all is working at the end of the year!

 

Fred G

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[glenn.f...@gmail.com]

Great. Keep it realistic.

 

Suggest you break #1 into two: 1) first build the ’88 exactly as specified in the Heath instructions, then 2) figure out what’s needed to upgrade it to an ’89 and do the upgrade).

 

I know you’re still counting the days ‘til retirement 😊

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[thego...@gmail.com]

Hi Glenn,

 

That is the plan.  Do you know anyone that has a cassette with HDOS on it?  That is the piece I don’t have.  If I can’t find that, I’ll build the H88, do all the test/checks, etc. and then add a floppy next.  Once that works, add memory, then add the serial card. 

 

And not that I’m counting days to retirement (81 total days, 57 working days) yes I can’t wait! 

 

The nice part about the next 3 months is I have no accounts assigned to me, I’m just training a new person so very low stress and it will give me time to start the H88 and get paid doing it 😊

To view this discussion visit https://groups.google.com/d/msgid/sebhc/001c01dc8026%24bae625f0%2430b271d0%24%40gmail.com.

[glenn.f...@gmail.com]

So it’s a bit of a misnomer to talk about “HDOS on tape”.  The D in HDOS is “Disk”.  Maybe HTOS? (Heath Tape Operating System)?  But back in the days of tape Heath didn’t have a brand for the whole system.  Instead it was a bundle of five components: 1) the Panel Monitor (PAM), which is actually in the firmware of the H8; 2) the console debugger (BUG-8); 3) the Heath text editor (TED-8); 4) Heath Assembly Language (HASL-8); and Benton Harbor BASIC (which came in two flavors BH BASIC, which needed only 8K of RAM, and Extended BH BASIC, which required 12K). The documents for these components are on the SEBHC site:

https://sebhc.github.io/sebhc/documentation.html

(scroll down to Software Reference…)

 

There are likely some SEBHC members with copies of these tapes, I’ll let them weigh in if they care to.  (I believe the H88 version was different than the H8 version?  Not sure.)  I’m not aware of any .WAV (audio scans) of these tapes on line. Mark Garlanger does have .WAV copies of HUG 885-1009 which is the first volume of Heath User Group software, which was released on tape.

https://heathkit.garlanger.com/software/library/HUG/

 

Another option is to modify your H88’s serial board to download files digitally.  The digital versions of the tools are on the SEBHC site:

https://sebhc.github.io/sebhc/software.html#Cassette_Tape_Images

 

 

• Glenn

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[norberto.collado koyado.com]

The H89 tapes used a different baud rate as the H8 tapes. I build an H89 controller to run on my H8 to create specific H89 tapes. 

Get Outlook for iOS

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Sent: Thursday, January 8, 2026 5:10:48 PM

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[Fred G]

Wow thanks for that info Glenn and Norberto. When I got my H8 in college it had the cassette tape interface. That is how I first started it up. I have so much to learn. Norberto, it sounds like you might have a way to make a cassette tape I could is to start/boot the H88?

Thanks,

Fred

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[B9]

Didn't someone on this list make a version of the H88 that runs in the MAME emulator? Since it is emulating at the chip level, it should be accurate enough to output a .wav file.

Even if that works, I think it is important that someone digitize the original tapes before they are lost forever.

--B9

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[Mark Garlanger]

Yes, I implemented the H88 and the cassette interface card in MAME. You can find more info about it on my site - https://heathkit.garlanger.com/emulator/mame/, and iirc, the wav files for the tapes at the bottom of that page were actually digitized from the original tapes.

Mark

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[norberto.collado koyado.com]

Yes, I can make H89 tapes on my H8 system. Let me order some tapes at Amazon. You will need a cassette player recorder to load them. At Amazon you can get one for under $40.00 dollars.

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Subject: H88 cassette tape. Was: [sebhc] It's 2026, where's your Heathkit at?

 

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[glenn.f...@gmail.com]

Great to see you have all the “HTOS” WAV files there Mark!

 

Fred: you can also use an electronic device to play these if you don’t have a tape player.  For example, I used an iPad to convert Mark’s .WAV files (the HUG tape) into digital form (H8T). As I recall I had to set the volume high (90%?):

https://photos.app.goo.gl/RuTojPLGfGNRrjzW9

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