Synchr030/S 256MB SDRAM Accelerator for the SE/30

[YMK]

Synchr030/S is a 256MB SDRAM accelerator PDS card for the Macintosh SE/30. It combines a custom memory controller with 256MB of SDRAM to double the SE/30's memory capacity and throughput. There's no longer a need to deal with broken SIMM slot tabs, dodgy contacts or aging SIMMs. Synchr030/S provides fastest possible 2-cycle reads and writes to the 68030 CPU, making it the performance equivalent of a 256MB L2 cache that never misses.

To enable 2-cycle reads, installation of the included /ECS Tap PCB is required. This small board fits over the CPU pins on the back of the logic board and routes the CPU's /ECS signal to the PDS card. This signal is not present in the SE/30's PDS connector:

A System 6/7 extension enables fast 2-cycle access to SDRAM and expansion to 256MB under System 7 with a IIsi-derived ROM, such as the Rominator II. The extension also performs ROM shadowing, which relocates ROM-resident Toolbox routines to SDRAM, where they can execute faster. Without the extension, the card operates as 128MB of DRAM with the stock 4-cycle access time.

The controller operates at 63MHz, providing a 32-bit data path to memory at a maximum throughput of 31.33MB/s. Unlike the stock DRAM controller, Synchr030/S does not stall for refresh cycles, so consistent access times are guaranteed. All signals through the card are unbuffered, routed directly to the PDS passthrough connector. The two large capacitors on the board are polymer and will not leak.

Connectix Maxima is supported under System 7, which enables large, disk-backed RAM disks. SDRAM-based RAM disks typically yield 4.5MB/s with the stock CPU, faster than any SCSI device.

/STERM and /DSACK signaling options are selectable via jumper for compatibility with CPU accelerators. Compatibility is confirmed with @zigzagjoe's Interware Booster 50-SE30F clone (with /DSACK) and @Bolle's PowerCache P33 (with /STERM). Both of these accelerators benefit significantly when paired with Synchr030/S.

On the rear of the PCB, three LEDs indicate various conditions. These are visible through the SE/30's frame, and MacEffects clear case:

• "ACCEL" LED (emerald): Indicates fast 2-cycle SDRAM access, after the extension is loaded.
• "/ECS" LED (white): Indicates activity on the stock CPU's /ECS signal. Will be off when a CPU accelerator card is in use, even if connected to the logic board.
• "FPU" LED (yellow): Indicates floating point unit access. This indicator is mirrored at the "FPU LED" through holes at the upper right corner of the PCB. An external LED header may be soldered here if desired. No resistor is needed.

MacBench 3.0 Results:

Performance summary:

MacBench 3.0 CPU score: +24%
Apple Personal Diagnostics 1.1.1 memory bandwidth: +70%


Specifications:

Power consumption: 0.43A @ 5V (2.15W) typical
Capacity: 256MB
Bandwidth: 31.33MB/s R/W
Clock speed: 62.66MHz
Slot space: C, D
Connections: SE/30 PDS male and female, expansion port, FPU LED
Weight: 123g
PCB construction: Eight layer, ENIG


Note:

• CPU accelerators may be sensitive to placement in the PDS chain.
• BMOW or other IIsi-derived ROM is required to enable 256MB under System 7.
• Basic soldering skills required for installation.

Special thanks for compatibility testing, accelerator insight and feedback:
@JDW @Bolle @zigzagjoe @MacEffects

Synchr030/S by YMK Devices on Tindie

Synchr030/S is a 256MB SDRAM accelerator PDS card for the Macintosh SE/30.

www.tindie.com

 

[JDW]

Folks, I've done extensive testing with this fabulous 256MB card, and have been pondering a video about it, but I've just been so busy with other video work (and my day job — man, I need to retire!) that I've not gotten around to it yet. And I do apologize for that because the blood sweat and tears that went into making this amazing card is simply incredible. YMK is to be highly praised for doing such innovative work!

You can have fun pestering the vintage Mac community with the question: "What's the maximum RAM I can install in an SE/30?" And when they all reply 128MB, you can fire back with: "Nope!"

Yes, yes... I know... You may thinking that even 32MB of RAM "is enough" in an SE/30, but consider the possibilities with a massive RAM DISK.

If you don't care about acceleration (which means the card RAM will run only as fast as stock RAM SIMMs would), you don't need to solder on the little /ECS Tap PCB to your motherboard. But of course, you would then lose one big advantage to having that card. Acceleration is pretty neat.

My notes have the following points of interest:

1. Up to 256MB of card RAM can be used under System 7, but only up to 128MB under System 6.
2. Extension is not required for the card to function. Those two files unlock acceleration, including the copying of ROM into fast SDRAM for improved toolbox routine performance.
3. All motherboard RAM must be REMOVED before using the card. (But this is a BENEFIT, actually. Many RAM sockets have broken tabs these days.)
4. Card does NOT disable RAM checks at cold boot. So if you don't install a custom ROM SIMM that kills cold boot RAM checks, you will spend an eternity waiting every time you flip on power. A custom ROM SIMM does not mean a stock IIsi, IIfx, or IIci ROM! Those ROM SIMMs are compatible, but they do not kill RAM checking at cold boot! Take note!
5. The ROM-inator II (with IIsi-derived ROM flashed), or similar custom ROM SIMMs from CayMac Vintage, Kero's Mac Mods, GGLabs, SiliconInsider, Garrett's Workshop is recommended to disable RAM checking at cold boot, and to enable extra RAM under System 7, and for the Extension to copy ROM contents to fast 2-cycle SDRAM.
6. Connector at the top is PDS “pass-thru” and is not for cache cards like the Turbo040. But accelerators like the DiiMO, or Ethernet cards like MacCon will work fine because they are true PDS cards, not cache cards.
7. The small "/ECS Tap" PCB is optional. It won't cause problems with any PDS cards you have installed in your SE/30 or even if you have no PDS cards installed at all. When that small PCB is installed on your motherboard and its jumper wire attached to the RAM Card, and when the Extension is also installed, it will boost memory performance from 3 cycle Reads to 2 cycle. The board is easy to install. It is to be soldered only at 2 points to the bottom side of the SE/30 logic board. A jumper wire leading from the small PCB to the PDS card must slide onto the /ECS pin that is on the RAM Card.

For many, the biggest reason to buy and install this RAM Card isn't the acceleration it offers or even the massive 256MB of RAM. It's broken RAM SIMM slots! Swapping those out is a real pain, and paying somebody else to do it is costly. Installing YMK's RAM card means you don't need to worry about those slots ever again, and you get a massive amount of RAM and in some cases RAM acceleration too! Plus your helping a small developer to continue to innovate and produce some insanely great stuff for the community. It's worth a look for any SE/30 owner!