PSone (PS1 slim) with OneChip, attenuated CSYNC and dual oscillators


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SKU: psone Category:


Heavily modified Sony PSone (PS1 slim) games console. Fully refurbished, with CD laser re-calibrated (laser voltage 11.6mV via rear potentiometer and pattern checked on an oscilloscope) and reading discs like new. The consoles may visually show slight wear and tear, but they are functionally very good and well-tested.

Modchip installed, for region-free unrestricted booting of games. Video circuitry tweaked for better quality on modern upscalers; ideal for live streaming of games on original hardware (none of that emulation rubbish).

This is a PAL PS1 Slim (PSone) with the following modifications performed:

  • OneChip installed. It’s a stealth modchip which disables the copy/region restrictions, allowed burned CD-R and imported discs to be used.
  • Dual oscillator mod; GPU has 2 clock inputs: one for PAL, one for NTSC. The NTSC clock is wrong by default, so RetroFreedom fixes it by replacing its 53.2mhz signal input with a 53.69mhz one, using an additional crystal oscillator. This fixes compatibility issues with modern upscalers for use with HDTVs, and also fixes a few issues in certain games
  • Attenuated CSYNC (composite video), to replace CVBS (composite video) and S-Video Luma. NOTE: This breaks composite video and s-video, which means that you *need* an RGB SCART cable (for consumer TV/upscaler) or BNC cables (for PVM) to use these machines that RetroFreedom sells. See below for recommended suppliers of these RGB cables.

Included accessories (NOTE: no video cables included):

  • 1 controller (dualshock)
  • 1 memory card
  • UK power supply, rated for 240V A/C input; if your country uses 120V, please use a step-up transformer. If your country uses different plug sockets than the UK, you can use a plug converter. Playstations sold by RetroFreedom will work in all countries, so long as you use the correct plug adapter (and a step-up transformer if your country uses 120V A/C, e.g. USA, Canada, Japan).

No video cables are included, but you can buy this separately from one of these companies (they cost more than cables on ebay/amazon because they are much higher quality, and fully shielded, so the picture quality will be much higher):

  • Retro Access (USA) (highly recommended. They make the best cables!)
  • Retro Gaming Cables (UK) (also good, and they sell RAD2X cables which convert analog RGB to HDMI, inside the cable inside, so all you need is the RAD2x cable)

Sample screenshot from OSSC, fully calibrated

You can get very high quality with any upscaler solution (RAD2X, OSSC or GBScontrol) as mentioned below, from one of the playstations RetroFreedom sells.

Here is a sample screenshot, taken from an HDMI capture card hooked up to an OSSC (click it for full size):

Note about upscalers for modern LCD/OLED TVs/monitors:

These playstations only output RGB, with attenuated composite sync (not to be confused with composite video! The yellow cables won’t work).

RetroFreedom strongly recommends purchasing an RGB SCART cable, from one of the suppliers listed above.

If you’re using a PVM, definitely order from Retro-Access *not* Retro Gaming Cables, especially if you need BNC cables (they make custom BNC cables with PS1 multi-out in mind).

If PS1/PS2 is going to be the only retro console you own, and you are not using a CRT, we recommend the RAD2X cable from Retro Gaming Cables. This cable properly handles 240p/313p and is very high quality (based on Mike Chi’s RetroTink product).

If you’re using a normal consumer CRT TV, or PVM with SCART on it, just use a SCART cable sold by one of the above suppliers. Don’t bother with sync stripper in the cable, because RetroFreedom’s playstations already output pure csync (attenuated to about 500mV).

If you’re going to be using *multiple* retro consoles in addition to PS1/PS2 on a modern flatscreen display, we recommend buying one of these upscalers plus one of the RGB SCART cables recommended:

The reason you want one of these is that most TV upscalers don’t properly handle progressive 240p/313p content (where only the odd or even scanlines are drawn to and one of the odd/even are left blank, which is a hack most old consoles did to get true 60/50fps). Most TV upscalers will treat these “progressive” images as interlaced video and those upscalers are optimized for DVDs and film, so they introduce a lot of lag in addition to producing image problems.

Meanwhile, all of the upscalers mentioned above are zero/low(and non-variable) input lag and properly handle progressive content; the OSSC in particular is capable of handling higher resolution like 480p (or even 1080i like on a few PS2 games when using component video cables) and can even accept RGBHV (VGA cable from a dreamcast, or RGBHV modded console). These aftermarket upscalers are highly recommended, if you want the best picture quality possible.

OSSC is also capable of sync on green, and can handle 480p and above on *RGB SCART* cables *if* there is no sync on green and the sync is a pure signal (e.g. csync-modded PS2 with sync on green disabled). We strongly recommend the OSSC, but RetroTink 2X-SCART and GBScontrol are also very good options.

OSSC is a very high-end solution, and can be tweaked heavily to get a pixel perfect output. It’s one of the best scalers available, and zero lag. It converts analog RGB into HDMI but you can also use VGA with a HDMI to VGA adapter. It also accepts component video input and even *RGBHV*.

GBS8200 with GBScontrol is a cheaper option. It’s a *low* (not zero) lag upscaler and upscalers to higher resolutions in VGA mode. It also (unlike OSSC which uses Bob de-interlacing) uses *motion adaptive de-interlacing* with *very low lag* which makes GBScontrol ideal for use with interlaced content (e.g. most PS2 games. Note that most PS1 games don’t have gameplay in an interlaced mode, but some of them have cutscenes/menus in interlaced mode).

RetroTink 2X-SCART is the easiest option, and gives very good results (similar to GBScontrol-installed GBS8200) but it’s a plug and play solution. Just plug it in and it Just Works. No mucking around, just plug the thing in and use it.

There is a hidden 4th option:
Buy OSSC *and* GBS8200(and install GBScontrol please!). RetroFreedom uses both, in its lab, for different things (OSSC mostly used when testing/tweaking and especially when checking for interference/noise on a video line, when modifying video circuits on consoles).

About OneChip

Unlike other regions, PAL PSone slim consoles have a check in the BIOS that restricts the ability to boot NTSC games. The OneChip contains a special fix for this, which basically is to make the console start in 60Hz mode by default, including at the BIOS screen, so that NTSC games will boot properly. (NTSC = USA/Japan and so on. European games are PAL).

Older non-stealth modchips (such as the oldcrow modchip) are always on, and constantly send the SCEA, SCEE or SCEI text expected when the PS1 BIOS checks this on the groove in the commercially pressed disc (burned discs don’t have this information, and can’t, but the modchip fools the PS1 BIOS region by sending the correct signal, which also allows therefore burned CD-R to boot). This check is supposed to fail after the game has booted, but succeeds on non-stealth modded playstations, which is how games detect a modchip in-game. The stealth modchips (such as onechip) turn themselves off after the game has booted, or after successfully changing disc in multi-CD games, and thus these anti-modchip games will not detect the presence of the modchip.

The OneChip is *stealth* which means that anti-modchip games (such as Japanese version of Ape Escape) will work. The modchip turns itself off after the game has booted, thus making itself invisible in games that try to detect a modchip.

Fun fact: Many Japanese consoles additionally check the territory information on the disc, so a modchipped japanese playstation will only boot Japanese games (including burned copies). The playstations RetroFreedom sells are PAL consoles and don’t have this check, so they will boot games from any region. Technically, a game could check what BIOS is present and refuse to boot if it’s not the right region (and check what video mode is in use, which the BIOS sets to PAL on a PAL console until a game changes it to NTSC mode), but no games ever did this, they just did the very simple check to verify whether or not a modchip exists and is sending the SCEE/SCEA/SCEI signal.

About dual oscillator mod

The GPU has two master clock inputs: 53.2mhz for PAL, and 53.69mhz for NTSC. This is because on PAL, 53.2mhz divides perfectly by 12 to create the 4.43mhz PAL subcarrier signal used on composite video. 53.69mhz divides perfectly by 15 to create the 3.58mhz NTSC subcarrier used on composite video.

Because in practise, unmodified PAL consoles only boot PAL games, Sony cheaped out and only ran 53.2mhz, into *both* clock inputs. This works perfectly fine. Technically, all playstations start in NTSC 60Hz mode but PAL BIOS quickly switches to PAL mode by default, so on unmodified PAL consoles that NTSC clock is only ever required for simply booting the console (without the NTSC clock, the console won’t boot at all, and without the PAL clock, 50Hz PAL mode won’t work).

Thus, by default a PAL playstation modded to boot NTSC games will have a 3.55mhz subcarrier on composite video, causing wrong colours. This is irrelevant to us, because the playstations RetroFreedom sells do not output composite video or svideo (only RGB, plus attenuated composite sync on the composite video and luma multi-out pins). However, that master clock also affects hsync/vsync timings; on a real NTSC console, in 60Hz mode the vsync will be roughly 59.9hz or so but on a PAL console it’ll be 59.3hz instead; this out of spec timing works fine on old CRT TVs when using RGB (or composite video with PAL60 mod) but causes major problems on a lot of modern upscalers; e.g. OSSC will stutter.

What I, Leah Rowe, do is this: cut (disable) the 53.2mhz clock going into only the NTSC master clock, but leave the 53.2mhz clock going into PAL master clock intact. I then simply wire up a crystal oscillator to 3.3v rail, and wire the outputted (via 220ohm resistor, as per schematics) 53.69mhz signal to the GPU master clock input for NTSC. This fixes the issue, resulting in perfect timing in 60Hz mode (same as on a real NTSC console).

There is an alternative to the above mod: dual frequency oscillator modboard, which wires into both clock inputs but changes the signal when detecting mode switch between 50/60hz mode. I don’t install this mod, because my method is more efficient (less parts, and it accomplishes the same task).

About C-sync

The playstation outputs RGB by default, even without modification. However, the composite sync signal (combining hsync and vsync) is not present; instead, it is derived from the composite video or luma signal.

*Most* RGB SCART cables available on the internet use composite video for sync. Most TVs/upscalers can use this just fine, and the necessary sync info is extracted from that signal. In some cases, such TVs/upscalers will just use the composite video signal and *not* RGB.

RGB is the highest quality analog signal possible on a playstation, but it is subject to a lot of interference from the subcarrier in the composite video line which is commonly used for sync.

SOME RGB cables will use sync on Luma instead. The Luma signal (part of s-video) is less noisy because it does not contain the subcarrier frequency, so higher quality RGB cables will use this signal.

One other problem: with sync on composite video or luma, some modern TVs, upscalers and converters will not work because they expect pure sync.

The playstation GPU outputs roughly 3V TTL composite sync, which can be attenuated to a more correct ~500mV level by using a 470ohm resistor (because in your TV there is a 75-ohm resistor to ground, on the line, which creates a resistor divider). Roughly 520mV (give or take) is the correct level for composite *sync* signals (just the sync signal, nothing else).

So what I (Leah Rowe) do is simply run a 470ohm resistor. I disable composite video output on the video DAC, aswell as subcarrier input on the DAC (reduces noise within the DAC). I then, via that 470ohm resistor, hook up to the same capacitor that was previously used for composite video. I cut luma on the multi-out and bridge that to what is now the sync pin.

By doing it this way, *all* RGB SCART cables will work properly, whether they use sync on luma or composite video.

NOTE: this is *attenuated* composite sync. If you require *TTL* (3v) composite sync, please say so and I (Leah Rowe) will ship your playstation without the 470ohm resistor (the sync line will be a straight line, hooking up to the capacitor). With or without resistor, that 220uF capacitor is necessary for AC coupling.

NOTE: unless you request TTL sync, your PS1 will output an attenuated sync signal. TTL is only required in specialist setups; for instance, certain RGB capture cards expect TTL sync. With TTL sync, you can still use normal SCART cables but you just put a 470ohm resistor on the sync line *inside the SCART cable*. On default/standard RGB SCART cables for playstation, the sync line is typically used for composite video and is a straight-thru connection which means the console outputs it already attenuated.