Amiga 500 fast RAM + IDE

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cmorley
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Amiga 500 fast RAM + IDE

Post by cmorley » Wed May 13, 2020 6:14 pm

Made some good progress with my fast 8M RAM upgrade for the Amiga 500. I modified it to generate the CPU clock and with a 68000P10 it will run at 13.7MHz just fine. I might build the overclock capability into the production device.. :-k

So 8MB of fast RAM + IDE interface :)

I might put 16MB of SDRAM on it to fill in some of the holes in the memory map & provide more fast RAM in the ranger RAM area. I think there is another MB or two in the memory map that could be added too for maybe 11.5MB or 12MB increase. 8)

Dev board:
Photo0935.jpg
Mandatory SysInfo screenshot:
Photo0937.jpg

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sydney
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Re: Amiga 500 fast RAM + IDE

Post by sydney » Wed May 13, 2020 7:45 pm

Woohoo!
I'd love one of those! I won't be able to afford one until I'm back to work but I will definitely be after one. Definitly keep the overclock!
I presume it fits in the cpu socket and if so is it fully internal? And it'll need kickstart 2 or 3 to have the code for the hard drive?
All I'll need after that is a super Denise and I'll be a happy chappy!
The Amiga is a great machine but to use it seriously you need extra ram and at least 1 extra floppy drive, a hard drive is ideal though.

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sydney
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Re: Amiga 500 fast RAM + IDE

Post by sydney » Wed May 13, 2020 7:51 pm

Looking at the Sysinfo screenshot, does it really say 1.11 times a standard 1200? Is that right?
Also why 13.7Mhz for the overclock?

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trixster
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Re: Amiga 500 fast RAM + IDE

Post by trixster » Wed May 13, 2020 7:58 pm

A stock A1200 has no fast ram, so everything shares the 2mb chip ram. This really slows down the 14mhz 020 as it sits waiting for it's chance to access thnis slower ram after the custom chips. if you fit some fast ram you pretty much double the A1200's speed.

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sydney
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Re: Amiga 500 fast RAM + IDE

Post by sydney » Wed May 13, 2020 8:08 pm

trixster wrote:
Wed May 13, 2020 7:58 pm
A stock A1200 has no fast ram, so everything shares the 2mb chip ram. This really slows down the 14mhz 020 as it sits waiting for it's chance to access thnis slower ram after the custom chips. if you fit some fast ram you pretty much double the A1200's speed.
Yeah. I knew about the fast ram doubling the speed but didn'trealise the bottleneck would have affected the performance so badly. Commodre really messed up with the 1200 didn't they? It was my first amiga and I loved it but it should have been so much better. I wonder what the performace would have been like if it came with 1mb chip and 1mb fast ram, with both being expandable on the motherboard.

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Re: Amiga 500 fast RAM + IDE

Post by trixster » Wed May 13, 2020 8:19 pm

it wouldve been a much more competative machine! commodore really made some bizarre decisions in their later years. in the 4000 the A3640 processor card was deliberately made as cheap as possible and without any local 32bit memory, so it too was crippled by motherboard ram speed. the 25mhz 040 should have been very rapid but it was hamstrung.

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Re: Amiga 500 fast RAM + IDE

Post by cmorley » Wed May 13, 2020 9:07 pm

sydney wrote:
Wed May 13, 2020 7:45 pm
I presume it fits in the cpu socket and if so is it fully internal? And it'll need kickstart 2 or 3 to have the code for the hard drive?
...
Looking at the Sysinfo screenshot, does it really say 1.11 times a standard 1200? Is that right?
Also why 13.7Mhz for the overclock?
Yes 68000 drop in board when done and dusted. You'll need patched kicstart or 3(?), 3.1 or 3.1.4 to boot from HD.

Yes a stock A1200 has no fast RAM so the 68020 CPU is somewhat crippled! 13.7MHz = 96MHz/7. 16MHz boots kinda but isn't stable.

Fast RAM makes aout a 25-30% difference on A500 if you're compute bound... if you're pixel pushing bound then it doesn't help as much. Chip RAM is slower to access but also gets blocked by DMA so the CPU has to wait sometimes.

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Re: Amiga 500 fast RAM + IDE

Post by marcusjambler » Wed May 13, 2020 9:09 pm

=D> Awesome...
I'm definitely interested in one if it works with A500+

Marcus

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Re: Amiga 500 fast RAM + IDE

Post by cmorley » Wed May 13, 2020 9:10 pm

trixster wrote:
Wed May 13, 2020 8:19 pm
it wouldve been a much more competative machine! commodore really made some bizarre decisions in their later years.
There FTFY :)

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Re: Amiga 500 fast RAM + IDE

Post by cmorley » Wed May 13, 2020 9:12 pm

I haven't tried it in the 500+ yet but it should work... it is supposed to!

If I knew enough about the ST then it could go in there as well :O

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Re: Amiga 500 fast RAM + IDE

Post by marcusjambler » Wed May 13, 2020 10:16 pm

Also hoping it will work along side my current 2mb upgrade [-o<

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Re: Amiga 500 fast RAM + IDE

Post by cmorley » Wed May 13, 2020 10:20 pm

I put one of my 2MB upgrades on that board (you can see the Gary adapter bypassed in the picture) and it has been runnin Keir's Amiga Test Kit memtest for the past 6 hours while overclocked. So far so good 8)

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Re: Amiga 500 fast RAM + IDE

Post by marcusjambler » Wed May 13, 2020 10:24 pm

2MB upgrades on that board
Is that the ribbon cable running south?

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Re: Amiga 500 fast RAM + IDE

Post by cmorley » Wed May 13, 2020 10:25 pm

No. The 2MB trapdoor card isn't fitted in the photo. The ribbon cable is the IDE cable going off to a CF adapter. I've also tested it with an SD adapter and a CF to SD card adapter- all work fine :)

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Re: Amiga 500 fast RAM + IDE

Post by trixster » Thu May 14, 2020 12:43 pm

Any thoughts about a MegAChip clone, chris?

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Re: Amiga 500 fast RAM + IDE

Post by cmorley » Thu May 14, 2020 12:47 pm

trixster wrote:
Thu May 14, 2020 12:43 pm
Any thoughts about a MegAChip clone, chris?
There's a French guy on amibay who does them tuxbar81 IIRC.

edit: I have wondered about an FPGA 8375 Agnus + RAM now they are getting more expensive.. but that would be a major development effort.

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Re: Amiga 500 fast RAM + IDE

Post by Barnabas » Mon May 18, 2020 9:48 pm

I like the sound of this - I think it would go nicely in the new A500++ board I've recently finished building, so would be interested in one of these for sure :D

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Re: Amiga 500 fast RAM + IDE

Post by cmorley » Tue Jun 02, 2020 7:14 pm

My PLCC to DIP adapter PCBs arrived today so I soldered one up and put a 68HC000 into this project.

Adapter jenga:
Photo0962.jpg
Obligatory sysinfo screenshot:
Photo0964.jpg
Yey success. This CPU runs quite happily at 36MHz in this setup. Quite the speed boost over a 7.1MHz stock A500 :)

I could get a bit more performace out by doing some tuning on the fast RAM. I'm quite pleased with this though as I didn't consider reclocking the CPU at all when I designed the development board. It's allowed me to learn quite a lot about 68000 systems.

Now I need decide what products to make out of all this :shock:

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Re: Amiga 500 fast RAM + IDE

Post by Boydie » Mon Jun 15, 2020 11:12 am

Just ordered an A500, so would be interested in one as well.
Probably ought to get a 2MB upgrade as well.

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sydney
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Re: Amiga 500 fast RAM + IDE

Post by sydney » Mon Jun 15, 2020 11:23 am

How did I miss that update? 36MHz? What speed is the cpu rated at?

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Re: Amiga 500 fast RAM + IDE

Post by cmorley » Mon Jun 15, 2020 11:29 am

sydney wrote:
Mon Jun 15, 2020 11:23 am
How did I miss that update? 36MHz? What speed is the cpu rated at?
It is marked as a FN20... what it really is is anyones guess.

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Re: Amiga 500 fast RAM + IDE

Post by Kazzie » Tue Jun 16, 2020 8:42 am

cmorley wrote:
Mon Jun 15, 2020 11:29 am
sydney wrote:
Mon Jun 15, 2020 11:23 am
How did I miss that update? 36MHz? What speed is the cpu rated at?
It is marked as a FN20... what it really is is anyones guess.
If you feel the need for speed, perhaps "Fast as N2O"? :wink:
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