DesTestMAX: A revolutionary new diagnostic ROM for the C64

It's not often I see a testing tool for the C64 that moves the needle, but I feel that the DesTest MAX ROM is one such test that should help more people fix more Commodore 64 computers.
-- Links
DesTestMAX:
factorofmatt.c...
Apple II March-U RAM test:
github.com/mis...
TRS-80 March-U RAM test:
github.com/mis...
XT March-U RAM test:
github.com/ki3...
Adrian's Digital Basement Merch store:
my-store-c82bd...
Adrian's Digital Basement ][ (Second Channel)
/ @adriansdigitalbasement2
Support the channel on Patreon:
/ adriansdigitalbasement
My GitHub repository:
github.com/mis...
-- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/...
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
www.rigolna.co...
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM Programmer: (The MiniPro)
amzn.to/2wG4tlP
www.aliexpress...
TS100 Soldering Iron:
amzn.to/2K36dJ5
www.ebay.com/i...
EEVBlog 121GW Multimeter:
www.eevblog.co...
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
www.ebay.com/i...
Magnetic Screw Holder:
amzn.to/3b8LOhG
www.harborfrei...
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
www.ebay.com/i...
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
www.retrotink.com/
Plato (Clone) Side Cutters: (Order Five)
www.ebay.com/i...
Heat Sinks:
www.aliexpress...
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Instructional videos
My video on chip removal without damage:
• How to remove chips wi...
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino

[@adriansdigitalbasement]

Small note: when I mention the zero page (and stack) is the first (and second) 100 bytes of RAM, I wasn't clear in the video that it is the first $100 of RAM when counting in hexadecimal. It's actually 256 bytes when counting them up in in decimal. Also, I was chatting with Matt about where people can buy a cart with the ROM already installed. He is looking to work with vendors so people can buy it directly without having to build one. Please check Matt's website (in the description) for more info, which is where he'll put updates as he has them.

[@danman32]

I was going to comment about your page size mistake.

[@thomaslindell5448]

@@danman32mission accomplished

[@herberttlbd]

Can you tell us what the silkscreen is on the cart Matt is using for the cart he gave you? His documentation doesn't give any specfic recommendations.

[@BrainSlugs83]

Not me, shouting at my screen, it's 256 Adrian! 😅😅😅 Very cool video btw. Keep up the good work. 🤘

[@emily1743]

Matt Desmond's software was the stuff of legends, great to see he's still creating stuff for Commodores today!

[@myleft9397]

Lol. He's fixed so many C64s he can't find a broken one...

[@danman32]

Late 80's I worked for a shop that had a cartridge with a 4x4 LED matrix to tell what chips were bad. Hardly needed anything on the board. CPU and I forget which chip provided the clock.

[@falksweden]

Every C64-video day is going to be a good day!

[@elmarschwarz535]

Really cool cartridge. Great video. Did not know that VIC II could display ROM.

[@twocvbloke]

Certainly makes it easier to sort out bad RAM before delving into something else being a problem, clever little creation there... :)

[@TheRetroChannel]

Cooooool!

[@tarajoe07]

I have zero interest in C64 but still watch every video because I just enjoy you fixing them.

[@Blood-PawWerewolf]

Annnd of course this gets released AFTER I ordered a 4-in-1 diagnostic cartridge from Retro Rewind…

[@jamesarthurreed]

Of course! Then again, you might consider this an opportunity: you could buy this, too, and upload a review comparing and contrasting their features and limitations....

[@Blood-PawWerewolf]

@@jamesarthurreed would it work on a flash cartridge?

[@jamesarthurreed]

@@Blood-PawWerewolf I don't know for a certainty, but given its flexibility in use, I'd be surprised if a working solution couldn't be created. I have no experience with this ROM, but I'm planning to get one now that I know about it.

[@thomasandrews9355]

We talked about me fixing one of these boards and having absolutely nothing happening...guess I know what I need to try now

[@josch1710]

Actually, the zero page is the first 256 bytes, not the first 100 bytes.

[@bozimmerman]

He's thinking hex $100 bytes. :)

[@josch1710]

@@bozimmerman What I also thought ;-)

[@adriansdigitalbasement]

Yes -- hahaha -- I need to pin a comment or I think I'll have about 10000 comments about it :-)

[@codahighland]

​@@adriansdigitalbasementDo you mean 10000 or 65536 comments?

[@retrozmachine1189]

With a bit of logic would it be possible to toggle the MAX line once the 4K only tests are done to flip the C64 back to normal mode and carry on testing all the RAM? Since the 6502 has no IO port space it'd need to have a sequence of writes to avoid false triggering the change back to normal mode during RAM tests, but still doable.

[@narayanbandodker5482]

Maybe you can send him some "known bad" chips so that he can try them on his board, and make adjustments to the firmware that detect these defects, and reports them properly

[@tony359]

Amazing!

[@RetroCaptain]

My cousin traded me some stereo equipment for his old Vic 20 after he was finished high school. He walked me through connection to the TV and startup. It showed the Commodore screen then boot screen then stayed stuck in "reboot" something like that. That's all it would do.

[@timothygrupp]

Tres trop bien!!

[@the_beefy1986]

If MAX mode is enabled by pulling a pin to ground, couldn't a simple switch be installed on the cart to switch between MAX and kernel modes?

[@tomteiter7192]

oh wow... I didn't know about the max mode... I wondered how the deadtest rom might work, but I never looked it up... And I call my self a collector... I'm ashamed...

[@williamsquires3070]

Oh, come on! When are they going to get around to doing February testing?? 😆🤣😝 (yeah, I’m biased here, I was a February baby.)

[@flagrama]

Red and Green to indicated different status are not colorblind-friendly.

[@dcarlin3]

How does the swiftlink version work? Do you need a cartridge port expander to plug in both the swiftlink card and the DesTestMax cartridge?

[@pb_magnet]

Do you think it would work to have a switch on the cartridge to disable Max mode and test the upper memory?

[@adriansdigitalbasement]

There could be two ROMs yes, with both versions on here. Or some kind of intelligent cart with a RP2040 would need to be created which could swap modes on the fly, first testing in MAX mode and then moving on to normal mode, or maybe some kind of DMA mode to test the RAM directly.

[@jandjrandr]

​@@adriansdigitalbasement Yeah, it could certainly do both in one cartridge, but it would need to toggle reset at the same time as switching off ultimax mode. The C64 would need to support writing to the ultimax ROM space for software to control the reset. This depends on whether the PLA allows writes to go to the cartridge address space by software, if not, a physical button is required. If the cartridge has a mapped register or RAM with a bit mapped it can trigger a software reset, and keep that RAM/register powered and write protected while reset is underway. This can also double as the ultimax mode switch. Since it is a simple on/off logic switch even some NAND gates setup as an S/R latch would work here. There are a few more details, but they aren't necessary for explanation. Reset tricks on C64 are limited to non rev-A boards of course unless they have the reset fix applied.

[@shmehfleh3115]

Does this work with the C128? I have a 128D with the dreaded black screen, and as you point out in your video, all I get from the dead test cart is a more-or-less randomly blinking white screen that doesn't tell me much.

[@alakani]

Dang that's cool, now I'm curious if anybody made one with an arduino in place of the rom, then it might not even need the cpu to work

[@andrewf9041]

Or if you can't burn it to an Eprom, is anyone selling the cart? A quick Google, couldn't find anything apart from Matts site. Thanks.

[@robertorenz7103]

so where do I buy a DesTestMax full working cartridge.. ?

[@herdware]

Huh, I did not that about the short board and U2 either.

[@charade993]

Hi!

[@smerf1979]

Did U checked supposedly bad 6526 in other board ?

[@bryondillon1302]

What cart PCB do you have that ROM installed in?

[@BobHannent]

Could this card act as a bootloader to launch the regular test afterwards?

[@mikb5165]

Neat!

[@Felice_Enellen]

Adrian, I think you should be clear that when you say "hundred bytes" you mean "hundred hex". Not all viewers will be clueful enough about 8-bit page sizes to know that's what you meant.

[@mikesilva3868]

Great 😊

[@AnnaDemersonon]

This video is like a drop of inspiration in the gray weekdays. Thank you for the positivity!🍑🍑 7 🦄!

[@MDYori]

GREAT! Sooo how do I get this cartridge???

[@Snowsea-gs4wu]

DIY by downloading the code from the link?

[@r0kus]

Your hex is showing.😦 Several times you talk about "100 bytes", when you mean 100 hex bytes, or 256 decimal. Probably most of your viewers will know what you mean, but it will be unclear to some people.⬅ Besides that distraction, very interesting product.

[@cmuller1441]

These days a small LCD screen is a few $ at most. Wouldn't it be better to have an external display the status ?

[@C64Lover]

I need to give this cart a go however I also welcome you to see my improved dead test in action, video: oNt4CL1cpOg - I made changes to the original corresponding my repair practice and convenience (especially text mode is set up early so you don't have to wait with black screen), itself being based on some other mod of dead test.