Sim Adapter and 16 MB SImm for CT60.

[CiH]

Hi there,

I'm thinking of an early Xmas/birthday present for self, which is to switch from a 4MB ST-RAM board, to a 14MB board for my Falcon.

The Falcon in question has an original first run CT60. The system as a whole was was refurbished by Doug Little recently. He did a brilliant job. .

The question is whether the 16MB 60ns Simm sold by Exxos is suitable for a CT60? It's sold adjacent to the unpopulated board in the Exxos shop.

Any existing customer reports of successful use with CT60, or recommendations for alternative CT60 friendly Simms are welcome.

[Steve]

Confused as you're jumping between ST-RAM, TT-RAM and EDO modules. What exactly are you looking to upgrade, your ST-RAM or CT60 TT-RAM?

[CiH]

Confused as you're jumping between ST-RAM, TT-RAM and EDO modules. What exactly are you looking to upgrade, your ST-RAM or CT60 TT-RAM?

It's the ST-RAM upgrade, as available from the Exxos Shop.

CT60 fast ram is already sorted. There's 256 MB worth. No issues there.

[Steve]

Well in that case you can either get the 14mb full module or the simm-type using that 16mb stick of ram.

[CiH]

There is only the unpopulated memory card and 72 pin SIMM in 4 MB and 16 MB flavours in the shop.

I'm guessing the 60 nanosecond (ns) is important. For a bit more context, my CT60 Falcon did have 14 MB before the CT60 was fitted, but that RAM did not agree with the CT60, so a 4 MB board replaced it.

More than a few things seem to like using lots of ST RAM, I'm looking at demos that use the NoCrew mp2 player. Also some newer standard Falcon software doesn't make concessions to lower amounts of ST RAM either.

[exxos]

@CiH The STram board doesn't have much to do with CT60.

I went with a simm socket as RAM tends to fail. So you can easily swap the simm out if that happens.

Also if you overclocked the main bus, you need faster STram. So again you can experiment with various simms as they are removable.

[exxos]

There is only the unpopulated memory card and 72 pin SIMM in 4 MB and 16 MB flavours in the shop.

You just get the card and 14mb simm.

I'm guessing the 60 nanosecond (ns) is important. For a bit more context, my CT60 Falcon did have 14 MB before the CT60 was fitted, but that RAM did not agree with the CT60, so a 4 MB board replaced it.

That doesn't sound normal. The CT60 shouldn't care unless you're overclocking the bus.

But you can have RAM faults which is why I developed this board..

viewtopic.php?p=93087#p93087

[dml]

CiH's machine has a Czuba-era CT60 with bus booster. I think it is 20MHz but it might even be 25MHz.

(you can confirm this with NEMBench and check the STRam speed in mono/hires - if it reads approx 150% on uncached reads, you have a 25MHz bus boost. 125% would mean 20MHz bus).

If 25MHz, I would make sure the STRAM board is 60ns for success. 70ns *might* work but I would try to get 60ns for that case.

[exxos]

When i had nemesis back in the day 25mhz would work fine some days then not others. Its likely I had 70ns back then.

[dml]

When i had nemesis back in the day 25mhz would work fine some days then not others. Its likely I had 70ns back then.

I still have one in my AB40/68040 machine and it works nicely so I'm trying not to open or disturb it for 20 years if I try to clean the board or tidy up the installation I know it will turn into a flaky mess.

The main problem I remember though from STRam being too slow for a bus booster is 'snow' on the display in various high res display modes. The CPU and main peripherals access the STRam at a lazy pace with waitstates etc. so they are quite insulated. The VIDEL though accesses the STRam much faster and when you go into high res modes 256 cols or TC, you start getting vertical columns of random snow every 16 or 32 pixels, as the VIDEL can't read the RAM fast enough. The CPU keeps going even when this happens,

(I'm talking about a plain Falcon here with a 20/24MHz bus, not a CT60 machine - that could be different)

So it's not a clear cut case of crashyness, it usually will start failing on the VIDEL fetches first. Crashyness will usually come from something else like clock skew or phase & noise problems at different parts of the board - which also get worse as you speed up the board. But the STRam speed itself is not something I saw causing crashes directly. Maybe it does become more of a problem with lower speed RAM at 80ns.... I don't remember.