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8032 Minimum RAM chips requirement to Boot

RizThomas

Experienced Member
Joined
Jan 2, 2012
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198
Location
Surrey,BC,Canada
Hello. Can somebody tell me what is the Minimum number of 4116 RAM chips required to be able to boot.
I have unsoldered all 16 RAMS and about to build a 4116 (MM5290J) Tester. I have this 8032 with busted screen and has been stored in a (damp) basement when I got it. I wasn’t getting any ‘Chirping’ sound even after installing a PET ROMulator.
Upon removal of all RAMs, I now get the Chirp sound when turned on. Of course, I don’t know if I have a video display.
So I’d like to test my original ROMs/RAMs if I can get the Chirp sound without the ROMulator.
Thanks
 
Not 100% sure for the 8032, but it will likely be 8 chips because in the PET each of the IC's provide one bit of data I/O and there are 8 bits, so it requires a minimum of 8 IC's to work.

But the actual memory amount required (at least in the 2001 PET) is 1k. It will boot with either 1k or 2k of memory. Better with 2k because then there is area above 0400h to test small programs. I know this because I created a system to run my PET from alternative SRAM memory, by deactivating the DRAM, so that the DRAM could be tested and diagnose the exact defective ones, that are soldered in, so that good ones are not removed from the pcb by mistake.

As noted in the article, if the PET boots with only 1k of memory present, there is an out of memory error reported ( ? OUT OF MEMORY ERROR IN 255) because BASIC checks above 0400h to find out how much working memory is available:


I developed this unique method for testing the 4116 IC, so they can be tested in the actual PET computer, which has the correct timing environment which support the 4116 IC's correctly.

The 4116 DRAM IC is a somewhat complex animal and there are some 4116 DRAM testers out there, which report them as faulty when they are not, leading a person up a very long garden path, into the neighbor's property, then up to the next street.

Having said that, I bought a number of 4116 DRAM testers to evaluate (I won't say who made the unreliable ones) but I will say that the better one I found, which appeared to match the DRAM check in the computer vs in the tester is this one:


So I think the person & seller who designed this one must have fully understood the 4116 and made a good tester, so congrats to him.
 
Correct. It is 8 chips in the lower bank of 16K.

The ROMulator contains my PETTESTER (if it will run) which requires no RAM to run and contains code to checksum the ROMs and tests the RAM - so there was probably no need to remove the chips.

Dave
 
Daver2 wrote “there was probably no need to remove the chips.”

Hi Dave...my 8032 has been in the backburner for while. I got it with a broken CRT and with some corrosions as if the system came from a damp storage. Long story short, after changing all white sockects, it did not give me a “chirp” sound with the original ROMs. I bought the Romulator, installed it but still no chirp sound. I have replaced the CRT chip but without success.
Lately, after removal of all RAMs, the board “chirped” so I suspect there must be something in the RAMs. I got the ROMulator very early in the development so I am not sure if Mike incorporated the PETTESTER. He customized it by adding an SJGray’s Edit ROM hoping the I can interface it with a composite monitor.
Now, after building the adapter, I get a consistent “garbage characters” in one line in the middle of the screen.
With this latest status, I hope it is actually outputting properly to a composite monitor.
I am currently in talks with BitFixer to reprogram ( to use a standalone programmer) my Romulator to incorporate the PETTESTER.
 
My next move is to build a 4116 RAM tester, install minimum RAMs, unsolder the Video RAMs too and test them. Then re-install original ROMs ( hoping they are good) and see if it still “Chirps”
With this setup, hopefully I could continue troubleshooting, even to the extent to use the 8032 PETTESTER and see what happens
 
My next move is to build a 4116 RAM tester, install minimum RAMs, unsolder the Video RAMs too and test them. Then re-install original ROMs ( hoping they are good) and see if it still “Chirps”
With this setup, hopefully I could continue troubleshooting, even to the extent to use the 8032 PETTESTER and see what happens
Hmmmm.... not a wise move.

I would not suggest building a 4116 RAM tester unless you are very familiar with the vagaries of the 4116 DRAM. They are quite picky about the timing requirements and then be prepared to modify the firmware so that your tester design actually works properly.

There are a number of 4116 RAM tester kits out there that are defective.

I devised a full-proof system to check them on the PET board as posted above.

Other ways that work are with Daver2's Pet Tester.

But if you feel compelled to buy an independent 4116 RAM tester,as I mentioned on this thread, this is the one I would go for because it works properly:


I have no association with this seller, but his is the only 4116 RAM tester, that I have found so far, that gives the same result as checking the 4116 DRAM in the actual computer.
 
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EDIT: I completely forgot to read fully your post ( first response) about the 4116 requirement. I apologize.

Thanks for the advise Hugo.
I was thinking of an Arduino (Nano) based tester but I will consider your advise. My 8032 also came with a RAM expansion board. It contains a few rows of 4116 unfortunately they, too, are soldered directly on the PCB.
I’d like to mention that a Composite adapter circuit that you recommended from another thread here is the one I built that somehow I get some display when connected with my 8032 board ( using the Romulator). However, as mentioned, the display is a consistent garbage characters in the middle of my screen. No scrolling.

EDIT: I will try again Dave’s PETTESTER with the original ROMs (and no RAMs) as he mentioned it does not require RAM, see if it Chirps and get a composite display
 
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Not sure if this has been answered already but the 8032 expects a full bank of RAM chips (unlike the 2001-8 where you can get away with only 4 chips to get it to boot). You can configure it for 16k only (bank 0) and then swap two resistors over to switch between the banks of 16k. I am typing this on my phone so need to consult the schematics to point to how to do this later
 
Ok found the info, you can swap the upper and lower banks around as per this link… but you need a full compliment of IC’s for each bank. It doesn’t isolate the bad IC though


 
Not sure if this has been answered already but the 8032 expects a full bank of RAM chips (unlike the 2001-8 where you can get away with only 4 chips to get it to boot). You can configure it for 16k only (bank 0) and then swap two resistors over to switch between the banks of 16k. I am typing this on my phone so need to consult the schematics to point to how to do this later
I don't think this is correct, a 4116 IC only holds one bit of data, therefore any PET model that uses them, must have a minimum of 8 IC's to boot, because it works with data bytes , the computer cannot operate with less than 8 IC's.
 
I think when Andy was referring to the 4 chips he was talking about a 2001-8 that doesn't use 4116 DRAM.

Dave
 
Thanks Dave, Hugo. I tinkered on my 8032 which I made a big improvement on my troubleshooting. I thoughI I got it beat but....
I am starting a new thread on it so we shelve this thread until I get my 4116 tester.
 
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