Here are some of the products in question, by the way:
Note that in both of these cases, these products appear to be primarily advertised for "industrial environments". As I understand it, "industrial environments" means that the product this drive would be used in is mainly intended to be solid-state all across the board (barring fans, etc.) and has to tolerate extreme low/high temperatures, with very little downtime. Speed is usually not a focus. These are products usually deployed in custom black-box products, or sometimes boxes along the side of a road somewhere (there's one near my apartment actually, from AT&T for their Uverse offering -- I can hear fans running inside of it, so it's probably a UPS + some servers/industrial hardware).
It's fairly obvious these products are being phased out, however. That's very, very apparent from both their websites.
The reason the prices for the PATA models is higher is because 1) they're less sought after and 2) they're mainly marketed towards military or industrial environments. I'm sure you're aware of the economics behind why the price of something which isn't bought regularly tends to increase, followed by it disappearing from stock entirely.
PCB-wise, yes, there is absolutely redesign needed on all levels. Actual PATA ICs are not pinout-compatible with SATA ICs (that almost makes it sound like the fact that they're ICs matters -- doesn't). Power/voltage requirements for these chips are different as well. Finally, the firmwares are *completely* different.
There were some god-awful first-gen SATA mechanical HDDs which actually used PATA-to-SATA bridge chips on their PCB (basically just a PATA drive with a bridge chip that converted PATA to SATA). Seagate and Western Digital I can confirm both did this briefly. This was a cheap and awful way for them to get-to-market a SATA-based hard disk. I don't want to talk about them. Those things were just awful. Awful awful awful.
My advice to you would be to NOT
invest in a PATA SSD. The reasons are as follows:
1. You will eventually have to upgrade your system, and when you do, there's a very good chance you won't have a PATA port on your motherboard (some boards today do not offer them any longer, and good riddance), so you'd be forced to buy a SATA SSD anyway (and do what with the PATA one? Sell it? To whom?)
2. TRIM is not available via PATA/IDE. It's an ATA8-ACS2 extension, which is significantly newer than what PATA/IDE drives offer protocol-wise.
3. NCQ is not available via PATA/IDE. PATA/IDE does offer what's called TCQ, but it was very rare. Safe to say those drives do not implement it.
4. Depending on the speed of the ATA controller on the SSD PCB, you're going to either be limited to 100MBytes/sec (ATA100) or 133MBytes/sec (ATA133), while the SSDs (SATA ones) you're looking at can easily do 2-4x that.
Because of all of these things, I would instead recommend you simply buy a SATA controller for your system. Because of the age of your system I imagine you only have standard PCI slots, so you're going to be limited to 133MBytes/sec anyway (maximum speed of standard 32-bit PCI). The choice would then be for you to invest in a SATA300 card (sure, you're not going to get 300MBytes/second with it, but newer SATA chipsets are more likely to have less compatibility issues with underlying drives, as well as better drivers) and get yourself whatever SSD you plan on using in years to come. Sounds simple enough, right? Wrong.
Finding classic PCI bus SATA controllers is becoming difficult. This is compounded by the fact that many first-gen SATA HBAs sucked (I'm looking at you VIA and Silicon Image).
One card I can recommend you is the Rosewill RC-217 (you do not have to use the RAID feature of the card):
Note that I recommend this card because it's driven by a Silicon Image 3124 chip (one of the few which can be trusted), has AHCI, and is inexpensive (US$30). But as I just said, this card is hard to find (out of stock most everywhere).
Do not go looking at these cards
(SATA150). Most of them are driven by Silicon Image 3114 chips, which you do not want (they have known silicon-level bugs).
So this puts you in a somewhat precarious position, given that you don't want to upgrade your system to a board that has SATA support (I understand why -- you'd need to buy a new CPU, RAM, etc.). I'm sorry to say the "best" or "easiest" choice you have is simply to buy a PATA MHDD (not SSD) and expand your capacity that way. Basically, you need to decide whether or not you want to upgrade your system now or stick with what you have + get a PATA MHDD for the time being (which you'll just have to replace later with SATA anyway). I can't manage your financial decisions.
Finally, I have to tell you right now (and this circles back to an earlier paragraph): please do not
. These things are well-known to cause CRC errors or "general issues" (drive falling off bus, I/O stalls, etc.). This is especially prominent with the ones that have exposed circuitry (no shielding), although the ones in plastic shells are just as worthless (same reason: no shielding).
Good luck with your decision.--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.