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Expand M8067 (MSV-11) memory board

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shirsch

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Today I set out to add another 256K of memory to a working M8067-KA memory board. After considerable study of the technical drawings and schematic it really looked as if the only difference between a KA and LA (512K) was the addition of 36 M2864 64Kx1 memory chips and the associated bypass caps. I checked all the new chips with a Retro chip tester and they passed. Problem is, the board still shows as being 256K (128KW). Has anyone done this mod themselves? I'm concerned I overlooked a jumper setting, but there don't appear to be any particular to the RAM size. The VMJA ECC/Parity test passes what's there, but seems oblivious to the added memory. There are two PROM chips on the board but the K and L variants call out the same DEC part number.

I'm a bit stumped. Anyone have thoughts?
 
I haven't done this board myself, but EK-MSV0P-UG-001_MSV11P_Aug81.pdf pages 11 and 12 have the configuration jumpers for the 64K chips. Check these first. Unlike other boards that have just one or two jumpers/swtiches, the settings required here are bit more complex.
 
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Yes, but mine already had 36 64K chips installed. Are you seeing a jumper setting that is qualified on the total amount of RAM rather than than the type of chip? I do realize there would have been a lot more to change if I were going from 16 to 64K parts.

UPDATE: I did find a jumper that configures the board for 18 or 22 bit addressing. Unless there's a typo, it's already setup for 22 bit. Since 18 bit addressing goes out only to 256K that looks like it could be the smoking gun. Just for fun I'll try adding the jumper and see what happens.
 
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That was going to be my thought as well - but Steve beat me to it. It is not link selectable to change the memory size, but involved a ROM change.

Unless you can find a ROM out of a -LA card and swap it, or work out the bit pattern and program a new one, you may have reached the end of your journey.

Dave
 
I once did a similar thing on a M8044 MSV11-D board. Removed all the 16k chips and replaced them with 64k chips. It involved programming a new PROM. Not too difficult to figure it out if you have the schematics.


miyVaHC.png
 
I have a M8067-LC (Same board but different memory supplier). Is there any way to read the prom w/o removing it from the board?
 
shirsch said:
VERY interesting. I wonder why the parts list in the drawings doc shows the same part number for both sizes? If anyone has the PROM images I have a programmer here. Otherwise I'll take a crack at figuring this out.
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Do you have blank PROMs (these are One Time Programmable)? And can your programmer program them? From cchhrriiss11's photo, it looks like the 1Kx4 (E37) is a 74S573 (NatSemi) and the 256x4 (E38) is a 63S141 (MMI)...
 
My programmer can read anyone's bipolar PROMs, but burns only 82S and 74S parts. I have the 256x4 chips on hand and have just ordered a couple of 1024x4 pieces from eBay.
 
wa2flq said:
I have a M8067-LC (Same board but different memory supplier). Is there any way to read the prom w/o removing it from the board?
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Probably not so easy to do while in circuit. It's likely I can work out the programming myself, but a friend of mine has kindly offered to pull and read out the parts from one of his boards. When I have all of them on hand I'll send copies to Al Kossow. These should definitely be on bitsavers.
 
It looks like DEC just used whatever parts they had on hand. One of my boards had two National 74S parts and the other an MMI 6301 and Signetics 82S137.
 
My M8067-L MSV11-PL board (or one of my boards, I probably have more than one) has an MMI 6301 256x4 TS for E38, and a TI TBP24S41 1024x4 TS for E37.

I could probably dump the contents of the two PROMs in circuit by sweeping the Q22 address space, while I have a logic analyzer attached to the DAL lines and the PROM outputs. Maybe I'll give that a try.
 
Mission accomplished. I picked up a 512k board on eBay and copied the E37 PROM. My modified board now passes all xxdp diagnostics as a 512k M8067. Turns out that only E37, a 1024x4 part, must be updated. I used an 82S137, but any 1024x4 device should be fine. Here is a zip with both 256k and 512k PROM contents.
 

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shirsch said:
Mission accomplished. I picked up a 512k board on eBay and copied the E37 PROM. My modified board now passes all xxdp diagnostics as a 512k M8067. Turns out that only E37, a 1024x4 part, must be updated. I used an 82S137, but any 1024x4 device should be fine. Here is a zip with both 256k and 512k PROM contents.
Click to expand...

Glad you were able to get the PROMs dumped and get your upgrade working. Good to have that info for the next person that comes along and wants to do this.

I still meant to try to dump the PROMs on one of my boards, but the usual case of too many projects and not enough time to get to them.

Did you happen to buy one of these? https://www.ebay.com/itm/225621773739
$50.00 (plus shipping) for a 512KB M8067 board seems like a reasonable price in the current market. I was tempted to buy one or two myself.
 
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