AST 4MB 64-Pin SIMM for GVP

[RiP]

Will these AST 4MB 64pin memory modules work with GVP?

[thebajaguy]

No - the pinout for GVP 64-pin SIMMs are unique.

Also, GVP 4MB SIMM32's are all 60ns, and IIRC uses a more rare 4K-type refresh part.

[hyami]

If you need GVP Simms, you can usually buy freshly made simms on Amibay. Worked fine for me.

[Kin Hell]

Originally Posted by hyami

If you need GVP Simms, you can usually buy freshly made simms on Amibay. Worked fine for me.

"Freshly" made GVP SIMMS!?

I wasn't aware GVP or any SIMM for that matter could go "Stale".

You're probably watching too much of the "Travel Show" on BBC1.

[hyami]

Originally Posted by Kin Hell

I wasn't aware GVP or any SIMM for that matter could go "Stale".

So you're one of the few you haven't come across a stale simm...

Lucky you! The sheer horror of a stale simm...

[RiP]

Originally Posted by thebajaguy

No - the pinout for GVP 64-pin SIMMs are unique.

Also, GVP 4MB SIMM32's are all 60ns, and IIRC uses a more rare 4K-type refresh part.

So what is this?

https://www.ebay.com/itm/334471303537

[Snoopy1234]

Originally Posted by RiP

So what is this?

https://www.ebay.com/itm/334471303537

With this item you will notice it has 9 ic's on it. The ninth one is the FPM component (Fast Page Memory) which is like an mmu for ram. While it is compatible with most Amiga simm based accelerators, the original memory simms were not FPM and would have 8 ic's usually for a 4mb stick.

As is mentioned previously, GVP branded Zorro expansions and other products had a specific requirement for GVP style simms only. I have a GVP TBC+ in my A3000 with such simms giving 8mb Z2 ram. I bought them on eBay listed as GVP 4mb simms.

[hooverphonique]

Originally Posted by Snoopy1234

With this item you will notice it has 9 ic's on it. The ninth one is the FPM component (Fast Page Memory) which is like an mmu for ram. While it is compatible with most Amiga simm based accelerators, the original memory simms were not FPM and would have 8 ic's usually for a 4mb stick.

No... It has 9 chips instead of 8 because it supports parity, meaning you can detect if a single bit of a byte has been flipped.
Why one of the ram chips in the photo of the linked SIMM is different from the others, I don't know, they are all 1Mx4 DRAMs.
If the SIMM supports FPM (almost all do), all the ram chips supports this, there is no separate chip for the FPM support.

[thebajaguy]

Motorola chose to ignore the use of the parity bit. That's the reason for the x8 or x32 -bit nature of SIMMs used by the Amiga.

During the late 1980's/early 1990's, 8-bit/9-bit memory on 30-pin SIMMs was the standard. 32-bit memory standards had yet to be established.

PC/Intel chose to use the parity bit, so there is always an extra bit, so x9 or x36 (and what became the 72-pin SIMM standard through the 'EDO' period). Later server memories went one further (ECC), and wit that, could repair one bit, and detect a second, in an 8-bit grouping. Desktops eventually dumped the parity bit detection. FWIW - You don't really want to know what goes on inside modern DDR3/DDR4 server memory today, which now has a form of self-healing properties/spares.

There has been an intermittent eBay seller from the UK which makes and sells the cloned GVP SIM32's. That's your best option.

[Kin Hell]

tbtorro designed some "fresh" GVP SIMM's a while back.

https://eab.abime.net/showthread.php...p+simms&page=2

https://www.amibay.com/threads/4mb-6...erators.94046/

Might be worth a P.M. at least.

[thebajaguy]

Originally Posted by Kin Hell

tbtorro designed some "fresh" GVP SIMM's a while back.

https://eab.abime.net/showthread.php...p+simms&page=2

https://www.amibay.com/threads/4mb-6...erators.94046/

Might be worth a P.M. at least.

I've had conversations with tbtorro in the past few years. He's stepped away from building them due to a relatively low yield. Even with his pick-and-place gear, his clone of the SIMM32 PCB needs another revision for better yields). Plus, the issue of ascending cost/harder to find the proper memory type.

[Kin Hell]

Originally Posted by thebajaguy

I've had conversations with tbtorro in the past few years. He's stepped away from building them due to a relatively low yield. Even with his pick-and-place gear, his clone of the SIMM32 PCB needs another revision for better yields). Plus, the issue of ascending cost/harder to find the proper memory type.

Fully understand....