27C400/27C800 EPROM emulator

[terriblefire]

Great work. This is what all my Amiga's need.

[GadgetUK164]

Looking very cool!!! Super useful if it can be programmed easily enough!

[cmorley]

I did a PCB to adapter to an Acorn Master MOS (1Mbit 128Kx8 mask ROM). Just sent the PCB order off.

Master MOS adapter.jpg

[cmorley]

Working well in a rev 5 Amiga 500. The data buffers are HCT so 5v CMOS output levels - won't require pull ups like a 27C400 does in a rev 5... The wire goes to the _RESET signal to get ROM swithcing from the keyboard with ctrl+A+A. (ROM switching can also be done via the USB which might be useful for synths, drum machines and other non-computer gear)

rev5_a500.jpg

Firmware is functional. I have features to add but the core functionality is proven working :D

[PaulJ_2.0]

Shut up and take my money!

[JanHolbo]

Hi!

Great product in the making!

I think if TerribleFire and Chucky test then the Amigas are covered.

I know that you seem to have Amigas covered. I would like to help out as well if you need though. I would pay the cost of both kit and P&P to Denmark, if it is not too expensive.

Is it possible to mix rom sizes? 4 x 256K images (1.2, 1.3, DiagRom) and 2 x 512K images (2.04, 3.1.4) ?

Again, great to have people like you and others making new hardware for the machines we grew up with and still love and use :-)

EDIT: I am using an A500 Rev 6a motherboard.

JanHolbo

[cmorley]

Is it possible to mix rom sizes? 4 x 256K images (1.2, 1.3, DiagRom) and 2 x 512K images (2.04, 3.1.4) ?

Only with manual switches. You need A17 connected to the Amiga for 512K image but controlled by the switching for a 256KB image.

Chris

[JanHolbo]

Is it possible to mix rom sizes? 4 x 256K images (1.2, 1.3, DiagRom) and 2 x 512K images (2.04, 3.1.4) ?

Only with manual switches. You need A17 connected to the Amiga for 512K image but controlled by the switching for a 256KB image.

Thank you for the answer. Checking on my 2.0 Rom it is a 2.04 (37.175) that does not support IDE boot.

Would putting DiagROM and 1.3 on 512K images together with 2.04 and 3.1.4 (4 x 512K images total) work?

Any preview on price and date of release for either a prototype or RC board?

Jan

[cmorley]

Would putting DiagROM and 1.3 on 512K images together with 2.04 and 3.1.4 (4 x 512K images total) work?

Any preview on price and date of release for either a prototype or RC board?

Yes that works. I have tried (4 of) 1.2, 1.3, 3.1, 3.1.4 & DiagROM.

If you set the module up as 4x 512KB ROMs and program a 256KB image my firmware programs it twice (so either high/low on A17 is the same ROM image). It also handles byte swapping at program time.

I know there is space in the memory map on an Amiga for an extra ROM but not what you can use that for. In 1MB mode with a flylead from the CPU or Gary you could use this from one module. Is this useful on an A2000 I don't know?

I have a few more of the prototypes. Some are destined for testing in other systems. Terriblefire isn't testing so I sent 2 to Chucky. I don't know how much they will be yet because I am going to get these assembled - batch size and economy of scale will make them cheaper but then I need to pay more money up front and greater risk if there is a fault with them. My aim is that these will be cheaper than the existing multi EPROM/ROM switchers that are for sale now.

Chris

[cmorley]

Working in an 8-bit machine. This is an Acorn Master using the ROM emulator/switcher to replace the 128KB MOS mega chip (contains MOS, ROMs & character set). ROM switching working from the BREAK key :)

I will send this off to a friend who uses his Master daily (he did Y2K fixes and assembled MOS images for various versions/configs including a OS 1.20 for better model B compatibility).

Photo0798_800.jpg