Well, it's not like anything else suddenly can go bad on that module.

the bus buffers are easy enough to test if you want to be 100% certain, but I would look at that PAL

I had a PAL on a SIMMCONN act a fool for me - would always show as 0kB DRAM available no matter what SIMM was installed, once I replaced it everything worked proper

I recall Wu made the PAL code available, so I guess I could replace it. But in reality, it takes so long to load large sound font banks that I find the Gold's onboard 4 MB sufficient for my patience. I have contented myself with using the 3.5 MB GM35REVC.SF2 sound font. The shelf-life of the SIMMConn I feel is more of a concern for the Value cards which only have 512 KB. I'll have to test my Value system next I pull it out. I won't be surprised if it is not working as well. From your experience, sounds like the PAL is to blaim.

The PAL chips have limited data retention time, on the worse side only a decade is specified as maximum. This is a general problem with charge capture based memory cells, all the NOR and NAND flash chips, CPLDs, EPROMs and EEPROMs are affected too and will eventually "expire". A reflash will fix this until next time.

I see. So it is likely that everyone's will go bad. Can the PAL be reprogrammed, or do I need a new one? Also was wondering if they can be replaced with something a bit longer lasting?

It depends on a particular part, many are reprogrammable. For longetivity you need to cherry pick a device with highest rated retention time. I don't know any to suggest since I never looked into it in any detail.

Tiido wrote on 2020-03-07, 23:14:

The PAL chips have limited data retention time, on the worse side only a decade is specified as maximum. This is a general problem with charge capture based memory cells

Sorry mate, but that is just plain wrong. PALs are programmed by blowing fuses, not by charging memory cells! This is irreversible and can only be done once. There's nothing limiting the lifetime of a PAL chip apart from the fact that any semi-conductor will die at some point of time.

What you probably had in mind is a GAL.

If the PAL chip on those old SIMMconns fail so early, they were probably of very low quality or not programmed within specs (too fast, with too little voltage, etc.). PAL chips have an interesting behaviour when a fuse is not fully blown: electrons may jump the gap and build up a conductive bridge over time, kind of "repairing" the fuse. However, this can only happen if the PAL chip is in use, not when it sits on a shelf.

I keep mixing up PALs and GALs, but and it doesn't help that there are devices that are reprogrammable and are still called PALs in their datasheet (and i think because GAL got trademarked by Lattice so others couldn't use that name).

Tiido wrote on 2020-03-08, 09:15:

it doesn't help that there are devices that are reprogrammable and are still called PALs in their datasheet

I'm pretty sure they are rather called PLAs in their datasheets, as that is the umbrella term for all these. But true, it's easy to mix up.

Thanks for the information. Unfortunately, my digikey and mouser hobby orders are done for the year, so I'll just add this PAL chip to my list for the next order, which is probably another year away.

I'd be interested to hear from others who got a SIMMConn 10+ years ago to see how repeatable this failure rate is.

derSammler wrote on 2020-03-08, 09:24:

I'm pretty sure they are rather called PLAs in their datasheets, as that is the umbrella term for all these. But true, it's easy to mix up.

For example in a datasheet I had lying around :

The PALCE16V8 is an advanced PAL device built with low-power, high-speed, electrically-erasable CMOS technology. It is functionally compatible with all 20-pin GAL devices

I have seen others (praticularly stuff not AMD and Lattice) that refer to themselves as a PAL in their datasheets while being reprogrammable (even without the "CE" part) so it certainly muddies up things. I always check the particular part's datasheet to be sure.

I took a look at an AWE64Value SIMMConn and an AWE64Gold SIMMConn. They have different PLD chips.

AWE64Value
Lattice GAL16V8B-15LJ

AWE64Gold
Cypress PALCE16V8-15JC

The datasheets (attached) indicate that both are re-programmable and contain 64x32 AND arrays. The GAL's datasheet claims to have 20 year data retention, while I was unable to locate the retention time spec for the PAL. It is possible that Wu programmed these all at once, e.g. 1998, or in batches, and I'm past the 20 year mark. The GAL's programmable type is listed as "EE PLD" while the PAL is "PAL Flash".

I had been planning on just cutting the leads of the PLD, but since they both claim to be re-programmable, it would be nice to save them. I'm not quite sure how to remove it. I have one of those "hairdryer" hot air guns but wasn't sure if heating the whole thing up will damage it. Don't really want to waste my chipquick on these either. Easiest is just to replace them.

Does anyone know what PLD is used on the Sedrashop's SIMMConn Revival? In the photos, a sticker is covering the part number. But, looking on digikey for an 8 macrocell, 20-PLCC, 9x9, 5 V, EE PLD, 15 ns reveals a Microchip ATF16V8B-15JU : https://www.digikey.ca/product-detail/en/micr … 15JU-ND/1118925

They are $1.32 CAD each. 5 ns PLD's are also available, but are double the cost. I'll have to see if either of my programmers can handle this.

serdashop uses the PALCE16V8

please do NOT use that heat gun you will wreck everything

just use the damn chip quik is it really that valuable?

Financially, it would be cheaper and quicker to cut the PLD and program a new one compared to using the QuikChip.

maxtherabbit wrote on 2020-03-10, 13:30:

serdashop uses the PALCE16V8

More specifically, the Revival uses PALCE16V8H-7JC/5.

You really should consider investing in a proper hot air rework station. If chip quick is as expensive as you make it out to be might pay for itself pretty fast 🤣

I have one of those cheap Chinese 853D stations and it made quick work of removing my bad PLCC PAL

It's on my list of things to do.

The PLD is only 5x5x2, costs $1, and is low priority for me. Think I'll save my unopened package of QuickChip for something more deserving; I've had it since 1995 after all. Put another way, I don't think it's "sponge worthy".

EDIT: The 853D hot air station only costs $16 USD shipped? Sure takes up a lot of space though.

feipoa wrote on 2020-03-11, 02:08:

EDIT: The 853D hot air station only costs $16 USD shipped?

I'm a big fan of inexpensive Chinese soldering gear, but that seems suspiciously low. I'd accessorize with an upgraded insurance policy.

$16 does sound crazy cheap but if you go through ebay they have a pretty bullteproof buyer protection, worth a shot

as far at the thing taking up space that seems pretty silly - I mean how many retro PC cases do you have laying around right? At least this is a practical tool